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Gear / Technical Help => Microphones & Setup => Topic started by: jerryfreak on March 05, 2008, 03:50:17 AM

Title: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on March 05, 2008, 03:50:17 AM
well, i received these yesterday, SN 134&135, always fun to be on the bleeding edge! they're only a few mm's longer than the end of a KC5 active cable.

http://flickr.com/photos/10466474@N04/2311424533/ (http://flickr.com/photos/10466474@N04/2311424533/)

(BTW, somebody wanted a picture of my 'universal ortf bar', there it is.

I was playing around with them a bit, i would describe them as a typical '3-wire' mic. Basically if you can give them 4-9V on the third wire, pure gold comes out of the other ones. :)

I built a simple (and I mean SIMPLE - one cap, one resistor) powering circuit kindly given to me by bernhard vollmer, and hooked the unbalanced outs from the mics to my V3 (grounding pin 1 and 3 on the V3, of course).

I close mic'd a monitor and recorded at two different volumes:

-monitor playing at a whisper with maximum gain on V3

-monitor playing at typical concert volume, V3 gain at the usual 35 dB

sounded great in both cases, in the louder test, the noise floor of the mic was down in the -70's as expected. The CMRs allow for the full SPL of the capsules (132 dB for an MK4). in the lower volume test, i could hear the self noise of the mic, but i also could clearly hear my voice whispering across the room.

When i get the time, i will be doing a controlled comp vs a CMC6. Schoeps claims the CMR has the same sound and specs (I suppose i could believe that with advances in miniaturization of components in the 30+ years since the CMC6 has been around.), we will see.

The fact that it works at all with my V3 and will still allow me to run a full on open rig with (hopefully) no compromises is a huge breakthrough in my book. Esp since it will make for a killer stealth rig when needed, using the same equipment as people are currently running with the at953s and dpa4061s, except for the bigger mics

this battery circuit literally sips power, 1mA per mic is nothing. i am thinking about switching from a 9V to the tiny 6V silver oxides the CMBI's use.

note that there are two different types of CMR, i got the version with the decoupling capacitor on the signal wire to protect the mics from inputs with 'plug in power', to allow for more preamp options.

i'm working with our favorite north-of-the-border preamp guru to come up with some fun stuff. Trying to get him to expand his talents into the miniature A>D world :)

FWIW, my 'all in one' miniature box of choice, Len's mic2496 didnt really work (yet?). i currently have it setup with voltage on the signal lines for my 2-wire DPA's, and was hoping the presence of the decoupling caps in the mics would eliminate the need for me to reconfigure it. I am gonna try to jumper it to eliminate any mic powering, and then pull power off of the same or a dedicated 9V with the mini-circuit bernhard gave me

stay tuned!


Title: Re: Schoeps CMR
Post by: shaggy on March 05, 2008, 04:01:19 AM
Jamie, do you got a Kwon bar around?  Can you see if the collar of the CMR fits the bar?

What is the cabling like?  Soft and pliable or rather stiff like the KC5 & KCY?

+T fer sharing!
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 05, 2008, 08:01:03 AM
i'm behind the times.
what is the CMR ?
Title: Re: Schoeps CMR
Post by: drewloo on March 05, 2008, 08:18:34 AM
Microphone Amplifier for Pocket Transmitters
CMR

    * specially designed for using SCHOEPS "Colette"-series microphone capsules with pocket transmitters
    * low power consumption: only about 1/20 to 1/48 that of a phantom-powered microphone
    * low-impedance, unbalanced output

A SCHOEPS Colette-series condenser microphone normally consists of a CMC microphone amplifier plus one of the many available types of SCHOEPS Colette-series microphone capsule, operating from a source of 48 Volt phantom powering.

However, such powering is not available when the microphone is used with a pocket transmitter, as is often the case in film and television production. As a result, SCHOEPS ”Colette” series microphones have been difficult to use for this purpose. Electret microphones have often been the only practical solution.

The SCHOEPS CMR microphone amplifier puts an end to that situation. The CMR allows any SCHOEPS ”Colette” series capsule (except the BLM 03 C active boundary layer capsule) to be used with pocket transmitters. As with electret microphones only a very low supply current is required, yet the CMR offers low output impedance and good immunity to interfererence. The biggest benefit of all, however, is SCHOEPS' well-known sound quality, which this amplifier delivers fully.

The robust connecting cable is reinforced with Kevlar fibers. It remains flexible at low temperatures, and does not twist.

What types of equipment can the CMR be used with?

If the input of the equipment provides 1 mA for a micro­phone at 4 Volts or higher, the equipment should be suitable.
The current list of compatible devices is available on here.
If in doubt, simply ask your SCHOEPS representative or dealer.

Output cable

In many cases you would only have to tell us the type of equipment and the desired cable length. We could then make up an output cable for you with the proper wiring and plug.

Lead arrangement of the two-conductor shielded cable:
Shield: ground (both signal and powering)
Blue: + pole of the power supply
White: audio output
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 05, 2008, 08:34:00 AM
Interesting.
but what would be the need for this in a "taper" situation ?

seems like it could pose more problems than solutions.  and who in their right mind would set up a stereo pair of these and then walk away to record from a different location ?
I could see that in orchestral settings / churches I guess.
Title: Re: Schoeps CMR
Post by: Shawn on March 05, 2008, 08:41:41 AM

well you don't have to use a wireless type setup nick. I believe the CMR is really just the cables, which have some elctronics in them. think of it like a nbox except you provide the battery box portion of it. does that make sense?
Title: Re: Schoeps CMR
Post by: Craig T on March 05, 2008, 09:36:54 AM
Well, not quite since the NBox also gives you about +20db gain as well as power for the caps.   At $500/cable, seems like a very expensive option, but I guess if you consider the cost of a kc5>cmc6, it really isn't.  So you'd still need a battery box or some kind of adaptor to use phantom off your preamp/recorder.  Assuming you could fit the simple circuit inside something like an XLR barrel, you'd have a "ccm" style system with the ability to change caps - something that always kept me away from the ccm's.

well you don't have to use a wireless type setup nick. I believe the CMR is really just the cables, which have some elctronics in them. think of it like a nbox except you provide the battery box portion of it. does that make sense?
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 05, 2008, 09:57:40 AM
huh...
i'll have to research this a little more
Title: Re: Schoeps CMR
Post by: jerryfreak on March 05, 2008, 11:45:17 AM
well considering the Nbox guy buys active cables to make his n-boxes, and a pair of cmrs are cheaper than a pair of kc5s and use less power/require less electronics, i think it would be a no-brainer for him to move toward using these.


Well, not quite since the NBox also gives you about +20db gain as well as power for the caps.   At $500/cable, seems like a very expensive option, but I guess if you consider the cost of a kc5>cmc6, it really isn't.  So you'd still need a battery box or some kind of adaptor to use phantom off your preamp/recorder.  Assuming you could fit the simple circuit inside something like an XLR barrel, you'd have a "ccm" style system with the ability to change caps - something that always kept me away from the ccm's.

well you don't have to use a wireless type setup nick. I believe the CMR is really just the cables, which have some elctronics in them. think of it like a nbox except you provide the battery box portion of it. does that make sense?
Title: Re: Schoeps CMR
Post by: jerryfreak on March 05, 2008, 11:59:02 AM
Measuring with my caliper, the collar  is the same as the kc5 at right about 8mm. i dont have a kwon bar, but i do have an SGC clip. it fits the CMR the same as the KC5.

Cabling is same schoeps style, rugged, but a little thinner. KC5= 4mm, CMR = 2.75 mm. Cable is two 22-24-ish conductors with a metal braided shield, and the same material on the outside as the KC5. should be very durable. so just by diameter alone, its a little more flexible, but it is fully shielded. i wouldnt describe it as 'stiff'

another advantage over cmrs vs kc5 for n-box - smaller cables running down your neck in a stealth situation!


Jamie, do you got a Kwon bar around?  Can you see if the collar of the CMR fits the bar?

What is the cabling like?  Soft and pliable or rather stiff like the KC5 & KCY?

+T fer sharing!
Title: Re: Schoeps CMR
Post by: Craig T on March 05, 2008, 12:54:32 PM
Nick doesn't use kc5's in the design.  They are his own proprietary cables, similar to a kcy but thinner.  He does use the schoeps collette connector to mate with the caps.  But I do agree, there might be some value to integrating the CMR's into the design.  Might make for a smaller/lighter nbox.  I'm more interested in the possible adaptation into a flexible-cap ccm type setup.

well considering the Nbox guy buys active cables to make his n-boxes, and a pair of cmrs are cheaper than a pair of kc5s and use less power/require less electronics, i think it would be a no-brainer for him to move toward using these.

Well, not quite since the NBox also gives you about +20db gain as well as power for the caps.   At $500/cable, seems like a very expensive option, but I guess if you consider the cost of a kc5>cmc6, it really isn't.  So you'd still need a battery box or some kind of adaptor to use phantom off your preamp/recorder.  Assuming you could fit the simple circuit inside something like an XLR barrel, you'd have a "ccm" style system with the ability to change caps - something that always kept me away from the ccm's.

well you don't have to use a wireless type setup nick. I believe the CMR is really just the cables, which have some elctronics in them. think of it like a nbox except you provide the battery box portion of it. does that make sense?
Title: Re: Schoeps CMR
Post by: ianstone on March 05, 2008, 01:09:46 PM
  I'm more interested in the possible adaptation into a flexible-cap ccm type setup.


me too. keep us posted on these developments. thanks for the reports jamie!!!
Title: Re: Schoeps CMR
Post by: jerryfreak on March 05, 2008, 01:25:47 PM
Nick doesn't use kc5's in the design.  They are his own proprietary cables, similar to a kcy but thinner.  He does use the schoeps collette connector to mate with the caps.  But I do agree, there might be some value to integrating the CMR's into the design.  Might make for a smaller/lighter nbox.  I'm more interested in the possible adaptation into a flexible-cap ccm type setup.


well, it will always require another component for powering, like you mentioned, as you dont want phantom on for these. Something like you described that was basically a barrel which consisted of say, a full-size male xlr, pins 1 and 3 jumpered inside to an unbalanced connection, with an internal battery (I'm thinking 6V silver oxide), and a 3-pin mini xlr out to the mics is totally conceivable, and would be the same size and shape as a conventional xlr connector. Alternatively, make the battery external, and just run a wire out to a 9V in your gear bag.
Title: Re: Schoeps CMR
Post by: Craig T on March 05, 2008, 02:18:55 PM
I think there's a relatively simple circuit to takte 48v phantom to 9v.  I used the DPA DAD6001 adaptors with my 4061's, the whole circuit was inside an xlr connector.  If the CMR's can run off 9v, I think someone with the knowledge/motivation could make something to allow connection to a phantom powered preamp without the need for additional batteries.  Of course, now you might be looking at something close to the size of a cmc6, so that might not make any sense.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 05, 2008, 02:36:26 PM
duh, i totally had a pair of those here last week when i was testing xpandingman's at943 setup. I'll see if i can borrow them. they had a 3-pin output if i recall, but im not sure if power and signal are on different wires. the 4061 is a 2-wire mic.

I think there's a relatively simple circuit to takte 48v phantom to 9v.  I used the DPA DAD6001 adaptors with my 4061's, the whole circuit was inside an xlr connector.  If the CMR's can run off 9v, I think someone with the knowledge/motivation could make something to allow connection to a phantom powered preamp without the need for additional batteries.  Of course, now you might be looking at something close to the size of a cmc6, so that might not make any sense.
Title: Re: Schoeps CMR
Post by: Todd R on March 05, 2008, 03:22:08 PM
Enough to make you want to consider moving to the darkside. :P

I'd imagine if these are low power consumption, 3 wire designs requiring 4-10v power that the Church ST-9100 preamp would work with them.  So $1100 for a pair of the CMR's and $200 for the ST-9100  -- comes in at about $1300, around the same price as the Nbox solution, no?  I have no idea how the ST-9100 would stack up to the Nbox, nor really if it would work (need to ask Chris).  But this might be another solution for a compact schoeps solution, much like the nbox, and perhaps easier to come by.

Fun stuff for the schoeps gang.  Wish there were a similar solution for the Milabs or neumanns.
Title: Re: Schoeps CMR
Post by: Church-Audio on March 05, 2008, 03:58:53 PM
Enough to make you want to consider moving to the darkside. :P

I'd imagine if these are low power consumption, 3 wire designs requiring 4-10v power that the Church ST-9100 preamp would work with them.  So $1100 for a pair of the CMR's and $200 for the ST-9100  -- comes in at about $1300, around the same price as the Nbox solution, no?  I have no idea how the ST-9100 would stack up to the Nbox, nor really if it would work (need to ask Chris).  But this might be another solution for a compact schoeps solution, much like the nbox, and perhaps easier to come by.

Fun stuff for the schoeps gang.  Wish there were a similar solution for the Milabs or neumanns.

I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris
Title: Re: Schoeps CMR
Post by: Javier Cinakowski on March 05, 2008, 04:45:28 PM
I need to stop reading this board, or get a better job......
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 04:21:27 AM
update: i did get it to work with the mic2496, i basically had to disable any power to the mics, tap power off of the main battery circuit, and use the battery circuit bernhard gave me. it would be trivial to mod the mic2496 in this way, although i have some other mods in mind. i wish there were some options for some other tiny quality A>D's out there, i hate being limited to only one option.
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 06, 2008, 07:04:12 AM
wow.
ok, so leme get this straight.
does this kit come w/the caps too for this money ?
or is it just the cables ?
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 06, 2008, 07:19:46 AM
ok, answered my own question.

so you can get these for $1100
plus another grand or so for mk4 caps and viola ?
Hmmmm......
Title: Re: Schoeps CMR
Post by: Shawn on March 06, 2008, 07:20:53 AM
plus a powering solution. that'll probably run you at least another $100-$200
Title: Re: Schoeps CMR
Post by: Nick's Picks on March 06, 2008, 07:40:12 AM
a couple hundred extra doesnt bother me when I'm talking about several grand.
:-)
Title: Re: Schoeps CMR
Post by: brianp on March 06, 2008, 10:06:27 AM
i wish there were some options for some other tiny quality A>D's out there, i hate being limited to only one option.

what's wrong with a Sony D50?
Title: Re: Schoeps CMR
Post by: Todd R on March 06, 2008, 10:21:05 AM
update: i did get it to work with the mic2496, i basically had to disable any power to the mics, tap power off of the main battery circuit, and use the battery circuit bernhard gave me. it would be trivial to mod the mic2496 in this way, although i have some other mods in mind. i wish there were some options for some other tiny quality A>D's out there, i hate being limited to only one option.

Jamie -- could you share the powering circuit Bernard gave you?  If it is just a resistor and capacitor, maybe you could just post a rough ASCII text version here.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 01:35:03 PM
http://simplefuels.com/CMR.jpg

resistor- $99 cents/ 5 pack
capacitor- $1.50
9V battery - $3.00

doesnt sound like hundreds to me.

plus a powering solution. that'll probably run you at least another $100-$200
Title: Re: Schoeps CMR
Post by: it-goes-to-eleven on March 06, 2008, 01:38:52 PM
Good work diving into those!

I'd consider dumping my cmc6's and kc5's to go this route but... I think I'd miss the balanced output when running split setups, ceiling rigs, etc.

It'd be interesting to check out the circuit but I imagine it is a custom IC schoeps had developed?

This is the 48v > dpa circuit that has been posted before.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 01:43:34 PM
i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris

Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 01:44:53 PM
again, the CMR is a 3-wire mic, and doesnt do well with voltage on the signal wire

Good work diving into those!

I'd consider dumping my cmc6's and kc5's to go this route but... I think I'd miss the balanced output when running split setups, ceiling rigs, etc.

It'd be interesting to check out the circuit but I imagine it is a custom IC schoeps had developed?

This is the 48v > dpa circuit that has been posted before.

Title: Re: Schoeps CMR
Post by: Shawn on March 06, 2008, 01:55:36 PM
http://simplefuels.com/CMR.jpg

resistor- $99 cents/ 5 pack
capacitor- $1.50
9V battery - $3.00

doesnt sound like hundreds to me.

plus a powering solution. that'll probably run you at least another $100-$200
you just going to slap those resistors together with the battery and leave them hanging in your gear bag? or or you going to build a box to house it all. how are you going to connect it to the cmr cables? what connectors are you going to use? do you hav ea soldering gun? solder? the box? do you know how to do it?

sure if you build the power supply yourself it won't be $100-200, but how many people is that really an option for? Nick probably could. I'm sure others could too, but 99% of the people on here couldn't. That's why we pay guys like nick to build cables, and guys like busman and oade to modify gear. if we could do it ourselves we would. you also have to ask yourself what kind of quality are you getting. Is there a better way to do it, that will have a positive effect on the sound? do you think church audio's preamp for these is going to cost $6.50? I doubt it. My guess it'll be $100-$200 at least. That'll be the type of thing that people without the capacity to build the power supply will be looking at buying. Unless soemone else wants to slap together $6.50 worth of parts with solder and hot glue and sell it for $50.

my point was $1100 for the cables and a grand or so for caps isn't the total cost. it's likely to be around 10% higher than that for most people.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 02:04:28 PM
well of course it doesnt include the preamp, neither does a CMC6. lets talk apples to apples here.

i was going to sink the power circuit in some epoxy with mini-xlrs on each end, still well under $20 in parts

As simple as that is, i'd be willing to build a handful of them for TS'ers for cost of parts.

if you need a pre anyway, sure, talk to chris, im sure the powering circuit will only add a nominal cost (if any, compared to a 3-wire pre) once he gets it figured out.

Again, apples to apples, compare the wide variety of cheap pres out there compared to something tha tprovides phantom power for a cmc6, that usually start at $400 and go way up from there.

BTW, i emailed the DPA circuit to bernhard and asked if something similar could be done with the CMR's.

I'm guessing it wouldnt like the 48V on the signal wire, but we'll see what he says

http://simplefuels.com/CMR.jpg

resistor- $99 cents/ 5 pack
capacitor- $1.50
9V battery - $3.00

doesnt sound like hundreds to me.

plus a powering solution. that'll probably run you at least another $100-$200
you just going to slap those resistors together with the battery and leave them hanging in your gear bag? or or you going to build a box to house it all. how are you going to connect it to the cmr cables? what connectors are you going to use? do you hav ea soldering gun? solder? the box? do you know how to do it?

sure if you build the power supply yourself it won't be $100-200, but how many people is that really an option for? Nick probably could. I'm sure others could too, but 99% of the people on here couldn't. That's why we pay guys like nick to build cables, and guys like busman and oade to modify gear. if we could do it ourselves we would. you also have to ask yourself what kind of quality are you getting. Is there a better way to do it, that will have a positive effect on the sound? do you think church audio's preamp for these is going to cost $6.50? I doubt it. My guess it'll be $100-$200 at least. That'll be the type of thing that people without the capacity to build the power supply will be looking at buying. Unless soemone else wants to slap together $6.50 worth of parts with solder and hot glue and sell it for $50.

my point was $1100 for the cables and a grand or so for caps isn't the total cost. it's likely to be around 10% higher than that for most people.
Title: Re: Schoeps CMR
Post by: Church-Audio on March 06, 2008, 04:32:46 PM
i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris


My preamp uses a split rail design.. that's why... It cant be done with my preamps power supply... I have a bias supply built in to power mics but it will not supply enough current to power these mics.. So I have to add a separate power supply to power the mics with. I know my design and what can be done and cant be done..  ;)
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 04:43:24 PM
is there something about the split rail design that prevents you from running the other tiny power circuit off of the same battery, with the two power supples in parallel? the current draw of the mic power circuit is so low, i would think that it would have a negligible effect on battery voltage.



i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris


My preamp uses a split rail design.. that's why... It cant be done with my preamps power supply... I have a bias supply built in to power mics but it will not supply enough current to power these mics.. So I have to add a separate power supply to power the mics with. I know my design and what can be done and cant be done..  ;)
Title: Re: Schoeps CMR
Post by: Church-Audio on March 06, 2008, 04:53:37 PM
is there something about the split rail design that prevents you from running the other tiny power circuit off of the same battery, with the two power supples in parallel? the current draw of the mic pwer is so low, i would think tha tit would have a neglible effect on battery voltage.



i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris


My preamp uses a split rail design.. that's why... It cant be done with my preamps power supply... I have a bias supply built in to power mics but it will not supply enough current to power these mics.. So I have to add a separate power supply to power the mics with. I know my design and what can be done and cant be done..  ;)
Yes because of the common ground.... its not quite as simple as it appears to be. Its not a question of total available current its a question of the virtual ground.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 06, 2008, 04:59:19 PM
i knew there was a simple answer in there. i must ground the mics to the mic2496 or v3 input ignal ground for them to work on those units as well.

is there something about the split rail design that prevents you from running the other tiny power circuit off of the same battery, with the two power supples in parallel? the current draw of the mic pwer is so low, i would think tha tit would have a neglible effect on battery voltage.



i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris


My preamp uses a split rail design.. that's why... It cant be done with my preamps power supply... I have a bias supply built in to power mics but it will not supply enough current to power these mics.. So I have to add a separate power supply to power the mics with. I know my design and what can be done and cant be done..  ;)
Yes because of the common ground.... its not quite as simple as it appears to be. Its not a question of total available current its a question of the virtual ground.
Title: Re: Schoeps CMR
Post by: Church-Audio on March 06, 2008, 05:01:59 PM
i knew there was a simple answer in there. i must ground the mics to the mic2496 or v3 input ignal ground for them to work on those units as well.

is there something about the split rail design that prevents you from running the other tiny power circuit off of the same battery, with the two power supples in parallel? the current draw of the mic pwer is so low, i would think tha tit would have a neglible effect on battery voltage.



i dont quite understand why this requires two 9V batteries, as the mics only use 1 mA each. you had also mentioned via pm that you had reduced the power consumption of the ca-ugly from 20 to 12 mA.

with the average 9V battery running for 350-450 mAH, i dont understand the need for two batteries.




I am working on a super stealth preamp for these mics. In the next few weeks I will have finished the design and be ready to sell them They will however require 2 9V batteries to operate one for the mics one for my preamp. I think that the box will end up being about 2 x the size of my Ugly preamp.

Chris


My preamp uses a split rail design.. that's why... It cant be done with my preamps power supply... I have a bias supply built in to power mics but it will not supply enough current to power these mics.. So I have to add a separate power supply to power the mics with. I know my design and what can be done and cant be done..  ;)
Yes because of the common ground.... its not quite as simple as it appears to be. Its not a question of total available current its a question of the virtual ground.
There are always simple questions but never simple answers... :P my solution is to use a separate power supply for the mics and avoid this issue all together.

Chris
Title: Re: Schoeps CMR
Post by: jerryfreak on March 07, 2008, 04:02:37 PM
bernhard said:

Hello Jamie,

from physical point of view it should be possible to power a CMR by P48 but we never develloped such a design. Se we cannot offer you some schematics.

With best wishes

Bernhard Vollmer
SCHOEPS GmbH
Title: Re: Schoeps CMR
Post by: shaggy on March 07, 2008, 06:59:40 PM
bernhard said:

from physical point of view it should be possible to power a CMR by P48 but we never develloped such a design. Se we cannot offer you some schematics.


The CMR was intended for battery pack sources, so this doesn't suprise me.  Bernhard will certainly go the extra mile to help, but at this point the application we are requesting (P48 powering) is something they never had intended for the CMR.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 08, 2008, 03:12:23 AM
Wait a minute.  Didn't somebody post a Schoeps schematic to drive one of their mics with phantom?  This was in the context of a general phantom adaptor for plug-in mics.

i beleive youre thinking of the DPA schematic, no?
Title: Re: Schoeps CMR
Post by: jerryfreak on March 08, 2008, 01:42:08 PM
if you dont want to waste power, the V3 and many other pres can be set to 12V phantom instead of 48V. I'd guinea pig this unit with my V3 and cmr if you want to build it. is there any remaining voltage on the signal wire to the mics that would potentially damage them?

 
Title: Re: Schoeps CMR
Post by: jerryfreak on March 08, 2008, 04:13:53 PM
well, these CMR's are the version with added decoupling capacitor (free, by request). I was digging back thru some old email and realized i misstated the purpose of the decoupling capacitor, its not there to protect the mic from bias/plugin power from the
preamp, but rather to protect the preamp from a bias existing on the mic output.

i was unsure if i needed it or not, and discussed any sonic disadvantage to having them there. he alluded to (i didnt really get it) that if both the mic and the pre have decoupling capacitors that it can act as a high pass filter of sorts. i'll try to cut and paste when im near my email box again. always a slight language barrier and i dont want to make them feel like im bothering them, they are a great helpful resource when needed. I sent two pres over there and they apparently spent days trying to make them work  and engineering was a bit frustrated, so i tried not to ask more questions than absolutely necessary.

Re: 48V vs. 12V, im sure mike or neal at grace could tell us the electrical consequences of running it either way.

if you dont want to waste power, the V3 and many other pres can be set to 12V phantom instead of 48V. I'd guinea pig this unit with my V3 and cmr if you want to build it. is there any remaining voltage on the signal wire to the mics that would potentially damage them?

 

Well if you're going to use a 12V supply, you'd need to drop the resistors much lower.  The mic can probably be directly driven off 12V . . . but the waste of power is current, not voltage.  If switching a preamp from 48V to 12V phantom power switches to a different set of supply resistors (it might; the standard for 12V is 680 ohm resistors), then you might not save much if any current.

Anyway, no, there is no DC on the signal pin (unless the mic has a DC bias on its output, which it might), but if you're worried about spikes, you could add a zener between pins 2 and 1 (on the mic side).
Title: Re: Schoeps CMR
Post by: Church-Audio on March 08, 2008, 04:22:14 PM
well, these CMR's are the version with added decoupling capacitor (free, by request). I was digging back thru some old email and realized i misstated the purpose of the decoupling capacitor, its not there to protect the mic from bias/plugin power from the
preamp, but rather to protect the preamp from a bias existing on the mic output.

i was unsure if i needed it or not, and discussed any sonic disadvantage to having them there. he alluded to (i didnt really get it) that if both the mic and the pre have decoupling capacitors that it can act as a high pass filter of sorts. i'll try to cut and paste when im near my email box again. always a slight language barrier and i dont want to make them feel like im bothering them, they are a great helpful resource when needed. I sent two pres over there and they apparently spent days trying to make them work  and engineering was a bit frustrated, so i tried not to ask more questions than absolutely necessary.

Re: 48V vs. 12V, im sure mike or neal at grace could tell us the electrical consequences of running it either way.

if you dont want to waste power, the V3 and many other pres can be set to 12V phantom instead of 48V. I'd guinea pig this unit with my V3 and cmr if you want to build it. is there any remaining voltage on the signal wire to the mics that would potentially damage them?

 

Well if you're going to use a 12V supply, you'd need to drop the resistors much lower.  The mic can probably be directly driven off 12V . . . but the waste of power is current, not voltage.  If switching a preamp from 48V to 12V phantom power switches to a different set of supply resistors (it might; the standard for 12V is 680 ohm resistors), then you might not save much if any current.

Anyway, no, there is no DC on the signal pin (unless the mic has a DC bias on its output, which it might), but if you're worried about spikes, you could add a zener between pins 2 and 1 (on the mic side).

I would never run these mics with out a decoupling cap the cap serves two purposes. 1 protect the mic from voltage present from the preamps input. 2 to protect the preamps input from the output of the mic. You are correct that a cap that is to low of a value can act as a high pass filter. I recommend 10uF poly cap for this application is very high value will guarantee nothing in the audible range gets effected. Most preamps have a cap on the input so its not 100% necessary in these conditions. But if your going to be building a supply and your not 100% sure about what your doing USE A CAP....

Chris
Title: Re: Schoeps CMR
Post by: darktrain on March 08, 2008, 09:32:28 PM
well, these CMR's are the version with added decoupling capacitor (free, by request). I was digging back thru some old email and realized i misstated the purpose of the decoupling capacitor, its not there to protect the mic from bias/plugin power from the
preamp, but rather to protect the preamp from a bias existing on the mic output.

i was unsure if i needed it or not, and discussed any sonic disadvantage to having them there. he alluded to (i didnt really get it) that if both the mic and the pre have decoupling capacitors that it can act as a high pass filter of sorts. i'll try to cut and paste when im near my email box again. always a slight language barrier and i dont want to make them feel like im bothering them, they are a great helpful resource when needed. I sent two pres over there and they apparently spent days trying to make them work  and engineering was a bit frustrated, so i tried not to ask more questions than absolutely necessary.

Re: 48V vs. 12V, im sure mike or neal at grace could tell us the electrical consequences of running it either way.

if you dont want to waste power, the V3 and many other pres can be set to 12V phantom instead of 48V. I'd guinea pig this unit with my V3 and cmr if you want to build it. is there any remaining voltage on the signal wire to the mics that would potentially damage them?

 

Well if you're going to use a 12V supply, you'd need to drop the resistors much lower.  The mic can probably be directly driven off 12V . . . but the waste of power is current, not voltage.  If switching a preamp from 48V to 12V phantom power switches to a different set of supply resistors (it might; the standard for 12V is 680 ohm resistors), then you might not save much if any current.

Anyway, no, there is no DC on the signal pin (unless the mic has a DC bias on its output, which it might), but if you're worried about spikes, you could add a zener between pins 2 and 1 (on the mic side).

I would never run these mics with out a decoupling cap the cap serves two purposes. 1 protect the mic from voltage present from the preamps input. 2 to protect the preamps input from the output of the mic. You are correct that a cap that is to low of a value can act as a high pass filter. I recommend 10uF poly cap for this application is very high value will guarantee nothing in the audible range gets effected. Most preamps have a cap on the input so its not 100% necessary in these conditions. But if your going to be building a supply and your not 100% sure about what your doing USE A CAP....

Chris


So if i am ready this right, you are making a competitor to the nbox chris? will it have a single in and what kind of connection, the nbox uses that 5pin switchcraft, could you do the same and would it be a fixed or variable gain? and most importantly...estimated cost?
Title: Re: Schoeps CMR
Post by: Church-Audio on March 08, 2008, 10:09:44 PM
well, these CMR's are the version with added decoupling capacitor (free, by request). I was digging back thru some old email and realized i misstated the purpose of the decoupling capacitor, its not there to protect the mic from bias/plugin power from the
preamp, but rather to protect the preamp from a bias existing on the mic output.

i was unsure if i needed it or not, and discussed any sonic disadvantage to having them there. he alluded to (i didnt really get it) that if both the mic and the pre have decoupling capacitors that it can act as a high pass filter of sorts. i'll try to cut and paste when im near my email box again. always a slight language barrier and i dont want to make them feel like im bothering them, they are a great helpful resource when needed. I sent two pres over there and they apparently spent days trying to make them work  and engineering was a bit frustrated, so i tried not to ask more questions than absolutely necessary.

Re: 48V vs. 12V, im sure mike or neal at grace could tell us the electrical consequences of running it either way.

if you dont want to waste power, the V3 and many other pres can be set to 12V phantom instead of 48V. I'd guinea pig this unit with my V3 and cmr if you want to build it. is there any remaining voltage on the signal wire to the mics that would potentially damage them?

 

Well if you're going to use a 12V supply, you'd need to drop the resistors much lower.  The mic can probably be directly driven off 12V . . . but the waste of power is current, not voltage.  If switching a preamp from 48V to 12V phantom power switches to a different set of supply resistors (it might; the standard for 12V is 680 ohm resistors), then you might not save much if any current.

Anyway, no, there is no DC on the signal pin (unless the mic has a DC bias on its output, which it might), but if you're worried about spikes, you could add a zener between pins 2 and 1 (on the mic side).

I would never run these mics with out a decoupling cap the cap serves two purposes. 1 protect the mic from voltage present from the preamps input. 2 to protect the preamps input from the output of the mic. You are correct that a cap that is to low of a value can act as a high pass filter. I recommend 10uF poly cap for this application is very high value will guarantee nothing in the audible range gets effected. Most preamps have a cap on the input so its not 100% necessary in these conditions. But if your going to be building a supply and your not 100% sure about what your doing USE A CAP....

Chris


So if i am ready this right, you are making a competitor to the nbox chris? will it have a single in and what kind of connection, the nbox uses that 5pin switchcraft, could you do the same and would it be a fixed or variable gain? and most importantly...estimated cost?

My preamp will be essentially a Ugly with two gain pots +20 db of gain adjustable. With a 5 pin mini xlr connector and a 3.5 mm output. And it will cost about $200.00
Title: Re: Schoeps CMR
Post by: darktrain on March 08, 2008, 10:34:59 PM
so could i use my actives with the 5 pin switchcraft(is there an adapter) or could you build one with the plug we nbox users already have?(see pic)or is that already a 5 pin mini xlr?

(http://a136.ac-images.myspacecdn.com/images01/115/l_64eb3e25860d4264fb7bd7e743bcf4ff.jpg)
Title: Re: Schoeps CMR
Post by: Church-Audio on March 09, 2008, 12:39:03 AM
so could i use my actives with the 5 pin switchcraft(is there an adapter) or could you build one with the plug we nbox users already have?(see pic)or is that already a 5 pin mini xlr?

(http://a136.ac-images.myspacecdn.com/images01/115/l_64eb3e25860d4264fb7bd7e743bcf4ff.jpg)

That looks like an amp connector.. It would be hard with out seeing the connector in my hands. So I can measure it and make sure its the same one.

Chris
Title: Re: Schoeps CMR
Post by: jerryfreak on March 09, 2008, 04:31:10 PM
Darktrain, the disciples of the watch demand that you go stealth testament
Title: Re: Schoeps CMR
Post by: darktrain on March 09, 2008, 06:31:53 PM
Darktrain, the disciples of the watch demand that you go stealth testament

Into the pit i go :veryevil:
Title: Re: Schoeps CMR
Post by: darktrain on March 09, 2008, 06:46:10 PM
Here is a pic with measurement chris, its a switchcraft twist lock connector, this sounds like it would be a nice unit you are developing, you said it would be "ugly" style, could you package it in your pre box, thats pretty small, if you can make it with that connector so i can use my current active plug i will be first in line for this lighter/more compact alternative

(http://a73.ac-images.myspacecdn.com/images01/10/l_f74ddf00b9f019a5a3d217f8fc167bc8.jpg)

(http://a255.ac-images.myspacecdn.com/images01/2/l_38ea67d15d469309db881ac64b9db29e.jpg)
Title: Re: Schoeps CMR
Post by: schoepsnbox on March 09, 2008, 09:38:56 PM
Chris, this preamp you are designing will be for the cmr cables correct? 

Sorry Nbox users, your Nbox cables will not work with this pre unless Chris plans on packing 48-60 phantom power in the ugly preamp.

Long live the 60 volt parade >:D ;D


Anyhow, if I got it right about these cmr cables, why not run them directly into a Microtracker with phantom on and have at it?  No?



Title: Re: Schoeps CMR
Post by: Church-Audio on March 09, 2008, 09:49:55 PM
Chris, this preamp you are designing will be for the cmr cables correct? 

Sorry Nbox users, your Nbox cables will not work with this pre unless Chris plans on packing 48-60 phantom power in the ugly preamp.

Long live the 60 volt parade >:D ;D


Anyhow, if I got it right about these cmr cables, why not run them directly into a Microtracker with phantom on and have at it?  No?





Sorry I misunderstood.. I thought that there was a new set of mics that would run on 8 volts bias? was I wrong?
Title: Re: Schoeps CMR
Post by: DSatz on March 09, 2008, 10:34:58 PM
Not a new set of microphones--it's an active cable arrangement for existing "Colette" (= CMC-series) capsules, with very low power consumption and the ability to run from relatively low DC supply voltages. It delivers a low-impedance, unbalanced signal.

Main thing is, it dispenses with the need for a microphone amplifier (body) if you connect it to suitable equipment. It was designed for use with pocket transmitters ("wireless microphones") and therefore doesn't have a terminating connector unless you order it with one, since there's no world-wide standardization in that field--each manufacturer and even each model has different plugs, pinouts and voltages.

--best regards
Title: Re: Schoeps CMR
Post by: schoepsnbox on March 09, 2008, 11:38:43 PM
Chris, this preamp you are designing will be for the cmr cables correct? 

Sorry Nbox users, your Nbox cables will not work with this pre unless Chris plans on packing 48-60 phantom power in the ugly preamp.

Long live the 60 volt parade >:D ;D


Anyhow, if I got it right about these cmr cables, why not run them directly into a Microtracker with phantom on and have at it?  No?





Sorry I misunderstood.. I thought that there was a new set of mics that would run on 8 volts bias? was I wrong?



The CMR cables for the Schoeps will be well suited for your pre, I would guess??
 I just wanted to make it clear that the Nbox active cables will not work with your preamp unless it supplies the proper voltage to polarize the capsule.   Gotta admit these cables sound pretty intersting, must be a dc>dc converter to step up the voltage to the cap.
Title: Re: Schoeps CMR
Post by: jerryfreak on March 10, 2008, 12:03:51 PM
maybe cause the MT preamp is lacking, and cant power a 3-wire mic?

Chris, this preamp you are designing will be for the cmr cables correct? 

Sorry Nbox users, your Nbox cables will not work with this pre unless Chris plans on packing 48-60 phantom power in the ugly preamp.

Long live the 60 volt parade >:D ;D


Anyhow, if I got it right about these cmr cables, why not run them directly into a Microtracker with phantom on and have at it?  No?




Title: Re: Schoeps CMR
Post by: DSatz on March 10, 2008, 08:09:06 PM
mshilarious, if electrets worked that way, you could power perpetual motion machines with them, no?

--best regards
Title: Re: Schoeps CMR
Post by: Javier Cinakowski on March 10, 2008, 09:06:08 PM
Yinz are dorks! 

 :)

(thanks!)
Title: Re: Schoeps CMR
Post by: jerryfreak on March 11, 2008, 12:31:05 AM
go stillirs

baldwin represent!

Yinz are dorks! 

 :)

(thanks!)
Title: Re: Schoeps CMR
Post by: jerryfreak on April 09, 2008, 03:07:02 PM
ok, so ive been playing with powering these from NADY CBM-40 phantom power supplies (the ones that come with AT943 mics)

out of the box, these are basically little transformers that provide an open-loop voltage of about 15.4V on the third pin of the mini-xlr out. when attached the the cmr bodies, they provide 10-10.5V to the mic (a little hot). with a little tweaking, they work, and they include a nice rugged casing and 90-110% of the circuitry we need, would be quicker than homebrewing a circuit

so i opened them up, and added a 3.7K resistor from the power pin to ground, which reduced the open-loop voltage to 9.5ish V. This was still a little close to the 10V spec so i also added a 1.5K resistor inline between the power lead and the mic, resulting in 4.9V to the mic (spec is 4-10V). i had these laying around,i would probably use a 500-700 ohm resistor in practice. Heres what they look like inside:

(http://simplefuels.com/top1.jpg)
(http://simplefuels.com/top2.jpg)
(http://simplefuels.com/bottom.jpg)

please excuse the hack soldering job, i tried a bunch of different things, and havent decided on the final version yet, your seeing the product of half a dozen hurry-up soldering jobs with a crappy 30w iron.

anyway, i wanted to post the pics, particularly for mshilarious, as im interested in the effect of what ive done here, esp in regard to just taking the resistor to ground, which creates an extra current flow. also any comments on the overall circuit design strategy and its implications/advantages/disadvantages for our use, both in terms of sonic quality and power consumption. i know the pics arent the best, but i think if we can figure out generally what the circuit is doing, i can measure resistances etc or read any cap values we need

ideally the transformer would be swapped for one that outputs 9V open loop, maybe swap a resistor or two without adding any components. although i dont know if transformers are a standard size and would fit that cutout int he board.

Also, berhnards simple powering circuit included a 1.5K resistor off a 9v (for two mics, and a 100 uF 'smoothing' capacitor as he described it between the power lead (on the mic side of the resistor and ground)

(http://simplefuels.com/CMR.jpg)

what is the purpose of this capacitor, and do i need to add this to this power supply.

i emailed bernhard last night and asked him about it, to which he replied "the CMR is not designed for being used with a phantom power. You may connect it that way at your own risk only. The high open loop voltage and the capability of high current peaks lead to a high risk for the CMR being damaged.". so i think its safe to say he's over it.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 09, 2008, 03:18:54 PM
btw, i also did a comp of mk4>(cmr vs cmc6)>V3 close mic'ing moitors, will post it up here in the next few days.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Javier Cinakowski on April 09, 2008, 03:31:46 PM
Quote
NADY CBM-40 phantom power supplies (the ones that come with AT943 mics)

The AT943 comes with a Audio-Technica phantom supply (AT8533), whereas the Nady is a common, cheaper alternative.  Many folks here use the Nady as they are carried by SoundPor's and are about half the price of the AT.  I would be willing to bet the AT has a much nicer transforer and parts....  Likely a better option for such expensive mics...
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 09, 2008, 04:07:35 PM
i def got the feeling this one is cheap. uses like 26 GA wire, connector literally fell apart when i opened it.

i'll check out the 8533 and see if i can get one and tear it apart

Quote
NADY CBM-40 phantom power supplies (the ones that come with AT943 mics)

The AT943 comes with a Audio-Technica phantom supply (AT8533), whereas the Nady is a common, cheaper alternative.  Many folks here use the Nady as they are carried by SoundPor's and are about half the price of the AT.  I would be willing to bet the AT has a much nicer transforer and parts....  Likely a better option for such expensive mics...
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 09, 2008, 07:01:37 PM
thanks much.

could you be a bit more specific on the specs on the diode and the caps - ie 'use tantalum caps of the same value', and 'you want a xxx value zener diode'





The resistor to ground drops voltage dependent upon the DC source resistance, as you have noted.  More than that, I can only guess, because I don't know what's inside the CMR.  I am kinda guessing it doesn't just use a single FET, or if it does, that it doesn't take signal off the FET drain.  So I don't think it does any harm, so long as the Nady transformer can tolerate the total DC current (one would hope).  It is probably current-limited by the circuit on the board.

The larger question is whether you want to use a Nady transformer with a Schoeps capsule  ???  Is there a need for a transformer at all?  I thought the Schoeps capsule was low-impedance output, unlike the AT capsules the Nady is designed for.  But I guess I don't really know that.  I also don't know if the Nady transformer is step-down . . .

Anyway, the Nady circuit looks like a simple voltage regulation with D1 and Q1, and a capacitor-coupled audio circuit.  This is actually pretty similar to my X-T circuit, except I didn't take the phantom through the transformer, because I wanted to save it for other things.

Rather than hanging resistors off the board, I would imagine that is a zener diode you are looking at for D1, so replace it with a more suitable value.  While you're at it, I would replace the capacitors with something nicer.  You shouldn't need another capacitor added, since one of those caps should be for filtration of the zener.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 10, 2008, 01:12:04 AM
thanks!

Zeners are straightforward; if you want 9V to the capsule, use a 9V zener.  However first, measure the zener they are using, and compare that to the supply voltage, as they might drop the voltage a little on the way.  Something like 6-7.5V should do, I would think.

Replace caps with the same value in Panasonic FC or Nichicon PW range.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Celac on April 12, 2008, 02:14:34 AM


The larger question is whether you want to use a Nady transformer with a Schoeps capsule  ???  Is there a need for a transformer at all?  I thought the Schoeps capsule was low-impedance output, unlike the AT capsules the Nady is designed for.  But I guess I don't really know that.  I also don't know if the Nady transformer is step-down . . .

Anyway, the Nady circuit looks like a simple voltage regulation with D1 and Q1, and a capacitor-coupled audio circuit.  This is actually pretty similar to my X-T circuit, except I didn't take the phantom through the transformer, because I wanted to save it for other things.


Hi,
I think the transformer is unlikely to provide voltage stepping for the phantom supply as phantom is DC and transformers are AC devices. It could provide impedance matching (as you surmise).  A likely purpose however might be to balance the output of the unbalanced capsule attached to the supply.

It would seem to be a little bit of a quality mismatch for the Schoeps mic, but I certainly have no hard data to base that assumption on.



edit: for clarity, sorry for the inept use of the quote function
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 12, 2008, 05:02:06 PM
correct me if im wrong, but it though tthat it was merely a decoupling circuit and should have a negligible affect on the audio signal. Would mshilarious's circuit be better in theory or practice?

thanks guys, i know a bit about electronics, but not the ins and outs of the effects of various components/circuits on audio.



The larger question is whether you want to use a Nady transformer with a Schoeps capsule  ???  Is there a need for a transformer at all?  I thought the Schoeps capsule was low-impedance output, unlike the AT capsules the Nady is designed for.  But I guess I don't really know that.  I also don't know if the Nady transformer is step-down . . .

Anyway, the Nady circuit looks like a simple voltage regulation with D1 and Q1, and a capacitor-coupled audio circuit.  This is actually pretty similar to my X-T circuit, except I didn't take the phantom through the transformer, because I wanted to save it for other things.


Hi,
I think the transformer is unlikely to provide voltage stepping for the phantom supply as phantom is DC and transformers are AC devices. It could provide impedance matching (as you surmise).  A likely purpose however might be to balance the output of the unbalanced capsule attached to the supply.

It would seem to be a little bit of a quality mismatch for the Schoeps mic, but I certainly have no hard data to base that assumption on.



Rather than hanging resistors off the board, I would imagine that is a zener diode you are looking at for D1, so replace it with a more suitable value.  While you're at it, I would replace the capacitors with something nicer.  You shouldn't need another capacitor added, since one of those caps should be for filtration of the zener.
[/quote]
Title: Re: Schoeps CMR
Post by: Church-Audio on April 16, 2008, 09:37:17 AM
ok, so ive been playing with powering these from NADY CBM-40 phantom power supplies (the ones that come with AT943 mics)

out of the box, these are basically little transformers that provide an open-loop voltage of about 15.4V on the third pin of the mini-xlr out. when attached the the cmr bodies, they provide 10-10.5V to the mic (a little hot). with a little tweaking, they work, and they include a nice rugged casing and 90-110% of the circuitry we need, would be quicker than homebrewing a circuit

so i opened them up, and added a 3.7K resistor from the power pin to ground, which reduced the open-loop voltage to 9.5ish V. This was still a little close to the 10V spec so i also added a 1.5K resistor inline between the power lead and the mic, resulting in 4.9V to the mic (spec is 4-10V). i had these laying around,i would probably use a 500-700 ohm resistor in practice. Heres what they look like inside:

(http://simplefuels.com/top1.jpg)
(http://simplefuels.com/top2.jpg)
(http://simplefuels.com/bottom.jpg)

please excuse the hack soldering job, i tried a bunch of different things, and havent decided on the final version yet, your seeing the product of half a dozen hurry-up soldering jobs with a crappy 30w iron.

anyway, i wanted to post the pics, particularly for mshilarious, as im interested in the effect of what ive done here, esp in regard to just taking the resistor to ground, which creates an extra current flow. also any comments on the overall circuit design strategy and its implications/advantages/disadvantages for our use, both in terms of sonic quality and power consumption. i know the pics arent the best, but i think if we can figure out generally what the circuit is doing, i can measure resistances etc or read any cap values we need

ideally the transformer would be swapped for one that outputs 9V open loop, maybe swap a resistor or two without adding any components. although i dont know if transformers are a standard size and would fit that cutout int he board.

Also, berhnards simple powering circuit included a 1.5K resistor off a 9v (for two mics, and a 100 uF 'smoothing' capacitor as he described it between the power lead (on the mic side of the resistor and ground)

(http://simplefuels.com/CMR.jpg)

what is the purpose of this capacitor, and do i need to add this to this power supply.

i emailed bernhard last night and asked him about it, to which he replied "the CMR is not designed for being used with a phantom power. You may connect it that way at your own risk only. The high open loop voltage and the capability of high current peaks lead to a high risk for the CMR being damaged.". so i think its safe to say he's over it.

Here is the real problem that transformer is in the signal path so its changing the sound of your mics. Its probably a $2.00 transformer.. If it were me I would find a way to interface your mics that did not involve a $2.00 transformer.

Chris
Title: Re: Schoeps CMR
Post by: jerryfreak on April 28, 2008, 02:43:19 PM

Here is the real problem that transformer is in the signal path so its changing the sound of your mics. Its probably a $2.00 transformer.. If it were me I would find a way to interface your mics that did not involve a $2.00 transformer.

Chris


so... better transformer, or no transformer? can you recommend a better option?
Title: Re: Schoeps CMR
Post by: Church-Audio on April 28, 2008, 03:03:26 PM

Here is the real problem that transformer is in the signal path so its changing the sound of your mics. Its probably a $2.00 transformer.. If it were me I would find a way to interface your mics that did not involve a $2.00 transformer.

Chris


so... better transformer, or no transformer? can you recommend a better option?

The best option would be a 48-7volt converter with a voltage regulator and a pure signal path no transformer crap. I think I might know someone who can build such a think if there was enough demand for it. Also I am working on the battery operated CMR preamp.
Title: Re: Schoeps CMR
Post by: jerryfreak on April 28, 2008, 03:34:18 PM
cool, whats your timeline on getting mine back to me? im kinda veering in other directions for lack of the pre.


Here is the real problem that transformer is in the signal path so its changing the sound of your mics. Its probably a $2.00 transformer.. If it were me I would find a way to interface your mics that did not involve a $2.00 transformer.

Chris


so... better transformer, or no transformer? can you recommend a better option?

The best option would be a 48-7volt converter with a voltage regulator and a pure signal path no transformer crap. I think I might know someone who can build such a think if there was enough demand for it. Also I am working on the battery operated CMR preamp.
Title: Re: Schoeps CMR
Post by: jerryfreak on April 28, 2008, 03:38:54 PM
is that even possible when decoupling power from a signal line aka phantom power?

I'm thinking about givining up on using the phantom in the V3 at all, and just building a b-box with schoeps uber-simple power circuit, which would be totally isolated from the audio (sans ground)


Here is the real problem that transformer is in the signal path so its changing the sound of your mics. Its probably a $2.00 transformer.. If it were me I would find a way to interface your mics that did not involve a $2.00 transformer.

Chris


so... better transformer, or no transformer? can you recommend a better option?

The best option would be a 48-7volt converter with a voltage regulator and a pure signal path no transformer crap. I think I might know someone who can build such a think if there was enough demand for it. Also I am working on the battery operated CMR preamp.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 28, 2008, 07:43:15 PM
what is Q1/PF5102 in that schematic? im not familiar with that symbol.

would you want to build me a test board with this setup to try? according to schoeps, each mic will draw 1mA, 4-10V is acceptable


The schematic I posted is pretty much a linear voltage regulator followed by filtration.  The currents involved are small, phantom supplies plenty, so a DC converter circuit is overkill for this situation, and a potential noise source if not well designed.

Mics don't generally use step-down DC converters unless for some odd reason they need gobs of current (the tube in the AT3060, for example).  Step-up DC converters are used where polarization voltage needs to be higher than 48V.  But if you have enough voltage and current from the phantom supply, a DC converter is not indicated.

Assuming the mic needs 2mA, we're talking around 0.08W of wasted power.  If you are concerned with power consumption, you can select supply resistor values to drop the exact voltage you want to hit that figure, but you'd need to know the CMR's current consumption, and it would limit flexibility with less than full P48 power supplies.  There is a way around that, as I mentioned earlier; I'll post it below--this is probably similar to the Nady, without the transformer (paste it into my earlier schemo).

But I don't think there is an off-the-shelf DC converter that is going to improve on that efficiency.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 29, 2008, 03:18:22 PM
I'll take two, please! ;)

seriously, id love to test it

Test board?  Heck, I have a PCB to do this that fits in an XLR!

Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Jhurlbs81 on May 08, 2008, 06:20:40 PM
interesting read.  Any updates, guys?
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on May 10, 2008, 02:17:35 AM
just an addition, as i didnt know there was outside interest in this topic. (I think im the sole cmr owner on this site?)

we had moved it to email, and i asked mr. hilarious the following question:

does it require any change to run from 12V
phantom? i just picked up a pre that has 12V phantom only, and i can easily jumper my v3
to either 12 or 48V.

i think we discussed that using 12V power would be a bit more efficient somewhere in
that thread.


his reply:

The power supply voltage doesn't matter, anything from 9V to 48V is good as long as it
can supply the necessary current--1mA if specs can be believed!

12V may be more efficient, depending on how the recorder/preamp works.  The power
regulation circuit of the adaptor will force the excess voltage (above 7.5V) to drop
across the supply resistance, which basically means the power loss is current * excess
voltage.  All things being equal, the closer the supply voltage is to the regulated
voltage, the less wasted power (this is why I always cringe when I read about people
using 7805 regulators on 9V batteries).  But all things aren't always equal; if in
switching from 48V to 12V, the preamp does the same thing the regulation circuit does,
it's going to be wasted anyway.  But I would expect a portable device would use a DC
converter to generate 48V; in that case 12V will easily be more efficient.

Either way, the adaptor doesn't care, it will work with any voltage up to 50V (over that,
its component ratings will be exceeded).


i was thinking about this later, and was wondering if the V3 would run longer powering a pair of CMC6s on 12V phantom vs 48V phantom? the mics use double the current at 12V, but thats still half the wattage compared to 48V. i think the V2 can be jumpered to 12V as well

when i get these adapters im gonna try to do some runtime tests with the following setups:

v3+cmc6@48V
v3+cmc6@12V
v3+cmr@48V
v3+cmr@12V
v3+cmr externally powered

and maybe the same with V2 if i have the time.

always nice to squeeze some more battery life out of your gear. there should be no sonic consequences to run cmc6s at 12V vs. 48V


Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Jhurlbs81 on May 10, 2008, 08:13:57 AM
So, Jamie can you dumb this down for me and explain what would need to go between these CMR cables and say a V3?

Very interesting option,
Jesse
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on May 10, 2008, 05:00:20 PM
well, you either need a small 9V battery box based on the simple schoeps resistor/capacitor circuit i posted earlier (in which case youd turn off phantom on the V3), or an adapter like jon is building, which decouples the phantom from the v3 and puts the proper power to the third wire going to the mic. i honestly dont really fully understand jons circuit, i dont know anyhting about FETs. but the idea is to cleanly decouple the power from the pin 1 of the v3 (phantom power is on the same wire as signal in a typical mic setup), and provide regulated power (4-9V) to the cmr, without introducing any noise. i tested the nadys in this thread, and they worked, but most circuit experts agreed that that is a cheap hack and theres a better way to do it.

one thing i forgot to ask jon, does your adapter ground pin 1 and pin 3 on the v3 side to allow for the proper termination of that balanced connection prior to connecting the unbalanced cmr?




So, Jamie can you dumb this down for me and explain what would need to go between these CMR cables and say a V3?

Very interesting option,
Jesse
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on May 21, 2008, 10:33:15 PM
got em today.

jon is the man!

I'll report back...
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: nottingham on January 13, 2009, 11:25:19 AM
Jamie,

I want to send out a big thank you for all your research on the cmr project. I could not be happier with this set-up.

http://www.archive.org/details/moon2009-01-10.SchoepsMK4

Ron
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: dennisrtyler on January 13, 2009, 12:02:56 PM
Jamie,

I want to send out a big thank you for all your research on the cmr project. I could not be happier with this set-up.

http://www.archive.org/details/moon2009-01-10.SchoepsMK4

Ron
that is a fantastic recording Ron. could you snap a few pics of your final set-up including the 620? thanks.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: nottingham on January 13, 2009, 12:32:21 PM
I made the main cables two different lengths so I could use them for undercover work if I need to without having to deal with extra cable. Always hated that with the DPA’s. The longer set of cables are not pictured. I also have different breakout cables one has rca’s and one has full size xlr’s so I can use with other pres if I want.

(http://i151.photobucket.com/albums/s141/nottingham_1/IMGP0171.jpg)

(http://i151.photobucket.com/albums/s141/nottingham_1/IMGP0172.jpg)

Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Javier Cinakowski on January 13, 2009, 12:39:44 PM
that is about as awesome as it gets!
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: dennisrtyler on January 13, 2009, 12:51:07 PM
very cool Ron and Jamie
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: NOLAfishwater on January 13, 2009, 04:03:52 PM
holy shit that is a small versatile setup.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Matt Quinn on January 13, 2009, 04:12:34 PM
Hmmm....how much would it cost me to get into something like this? And I thought you still needed a preamp?
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: mmedley. on January 15, 2009, 11:11:45 AM
That is an awesome setup. Very neat and organized. I don't do undercover, but a setup that small would be awesome to have instead of the CMC6's. :hmmm:
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: nottingham on January 15, 2009, 02:39:03 PM
I don’t do undercover very often, but it’s nice to have the option. I wanted this compact set-up mostly to get to the impact zone in the small clubs I record in, without much impact on the people around me.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: johnw on January 26, 2009, 05:56:27 AM
I have been going back and forth on the CMRs vs an NBox and eventually decided on the Nbox due to the lower sensitivity of the CMRs (about 60% compared to CMC6 or other preamplifiers). In researching the CMR I did come across another option for powering these, the AKG B29

(http://www.bhphotovideo.com/images/largeimages/271337.jpg)

Only problems with this are it attenuates by -50dB, so you'd want to keep the levels on the sides all the way up. It also appears to have a 3 pin XLR out, so it takes 2 mics and mixes it down to a mono signal. But you could always use one box for each CMR or perhaps replace the 3 pin XLR out with a 4 pin and use a breakout cable.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on March 02, 2009, 03:49:40 PM
i just got mics 3 and 4 today.

SN 133 and 126. Weird, the ones i bought last year were 134 and 135. They must not be selling a lot of these.

hampton 4-mic here i come
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Sunday Driver on March 03, 2009, 02:19:21 AM
Hmmm....how much would it cost me to get into something like this? And I thought you still needed a preamp?

He is using the mic input on an Oade modified PMD-620. You don't need a preamp to use the mic input.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: nottingham on March 04, 2009, 06:42:32 PM
If anybody is is wondering how this sounds with the R-09HR mic input.



http://www.archive.org/details/mh2009-02-14.SchoepsMK4
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: (Evan) on March 24, 2009, 03:55:29 PM
Has anyone made a mini preamp for these yet?
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Church-Audio on March 25, 2009, 12:24:22 PM
Has anyone made a mini preamp for these yet?

I have made a preamp for the cmr its based on my ugly preamp it runs on two 9 volt batteries.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Matt Quinn on March 26, 2009, 07:49:19 AM
Has anyone made a mini preamp for these yet?

I have made a preamp for the cmr its based on my ugly preamp it runs on two 9 volt batteries.


Seriously? More info asap please! I'm about to pull the trigger on an N-Box,but seems like the CMR route could be a little cheaper, which would be great.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Church-Audio on March 26, 2009, 10:16:03 AM
Has anyone made a mini preamp for these yet?

I have made a preamp for the cmr its based on my ugly preamp it runs on two 9 volt batteries.


Seriously? More info asap please! I'm about to pull the trigger on an N-Box,but seems like the CMR route could be a little cheaper, which would be great.

It is my ugly preamp 00- 20db of gain two individual gain pots and its about 3x3x1 inch and takes two 9 volt batteries one for bias supply and one for the preamp.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Chuck on March 27, 2009, 04:11:17 PM
Jon recently built me a couple PFAs (his name for the voltage converter/ circuit balancer that fits into an XLR housing) for my Franken-Naks. The three wires per microphone configuration.

I had a chance to very briefly test the PFA's against my AT8533's. The audio output was much better than that from the AT8533's and the PFA's are smaller and lighter than the AT modules.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Sunday Driver on March 29, 2009, 03:27:00 PM
Jon recently built me a couple PFAs (his name for the voltage converter/ circuit balancer that fits into an XLR housing) for my Franken-Naks. The three wires per microphone configuration.

I had a chance to very briefly test the PFA's against my AT8533's. The audio output was much better than that from the AT8533's and the PFA's are smaller and lighter than the AT modules.

Do you know what the output voltage was? Was it less than 12 volts? I would love to replace my Nady CBM-40T adapters, pictured in this thread, with two of those.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Chuck on March 29, 2009, 06:30:30 PM
9v DC.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Roger Gustavsson on March 30, 2009, 06:23:24 AM
Jon recently built me a couple PFAs (his name for the voltage converter/ circuit balancer that fits into an XLR housing) for my Franken-Naks. The three wires per microphone configuration.

I had a chance to very briefly test the PFA's against my AT8533's. The audio output was much better than that from the AT8533's and the PFA's are smaller and lighter than the AT modules.



Aha, that is why you are selling your AT8533!

Roger
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Chuck on March 30, 2009, 09:44:49 AM
Yeah. For me, it's a better solution.
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on April 14, 2009, 04:18:47 PM
i just did a bunch of comps last night

4v>cmr>church ugly>R09 line-in
4v>cmr>church ugly>R09HR line-in
4v>cmr>batt box>R09HR line-in
4v>cmr>batt box>R09HR mic-in lo sens
4v>cmr>batt box>R09HR mic-in hi sens
4v>cmr>batt box>R09 line-in
4v>cmr>batt box>R09 mic-in lo sens
4v>cmr>batt box>R09 mic-in hi sens

will upload when i can
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: OOK on April 15, 2009, 08:02:11 PM
Jon recently built me a couple PFAs (his name for the voltage converter/ circuit balancer that fits into an XLR housing) for my Franken-Naks. The three wires per microphone configuration.

I had a chance to very briefly test the PFA's against my AT8533's. The audio output was much better than that from the AT8533's and the PFA's are smaller and lighter than the AT modules.


HHHMMM very interesting......got any pictures......

Peace
OOK
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: Chuck on April 15, 2009, 08:53:41 PM
I am very happy with the PFA adaptors I recently bought from Jon. As he said, everything is bult into Neutrik XLR connectors.

Here is a link to the PFA: http://www.naiant.com/studiostore/cleverdevices.html

I bought them to replace the AT8533 phantom power modules I had for my Franken-Naks. They are smaller and lighter than the AT8533's and don't use transformers for impedance matching.

Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: dactylus on March 16, 2010, 02:26:12 PM

...note for future reference in lightening those gear bags...

 ;)

Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: NOLAfishwater on May 10, 2010, 01:21:46 PM
I found what I was looking for
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on February 02, 2019, 03:01:38 AM
hey now!

time to revive this old dog of a thread as im about to order my lectrosonics SPDR which can power the CMRs directly (same front end as all the transmitters they make, which these are designed for)

so basically CMR specs look like this
(https://i.imgur.com/n6FOV3t.png)

lectrosonics front end looks like this
Dynamic mic: 300 Ohm impedance, 0.5 mV to 50 mV input level

Electret lavaliere: Input is virtual ground with servo adjusted constant current bias (very low impedance), Nominal 2 mV to
300 mV input level

Line level: 2.7 k Ohm impedance, 17 mV to 1.7 V input level

(https://i.imgur.com/KWV9ZiH.png)

lectrosonics recommended wiring to mic-in as follows:

Quote from: lectrosonics
Schoeps shield to pin 1
Pin 4 jumped to pin 1 (shuts off servo bias)
Schoeps blue wire to pin 2 (+5 Volts)
Schoeps white wire to a 1.5k resitor in series with pin 3 (audio in) You can substitute a 500ohm resistor for the 1.5kohm resistor if you are looking for more gain.

i asked bernhard about this he said

Quote from: bernhard
"That resistor controls the gain. The smaller you choose it the higher the sensitivity of the input - but this may lead to overload for higher SPLs. We do not recommend to choose the resistor such small, we would use 3k3."

so basically if the resistor is too small it might (brickwall?) the input? in another email Bernhard said

Quote from: bernhard
any resistor in line with the mic in will increase the ground noise floor, so we recommend to keep it as low as possible, this means adapted to the maximum sound pressure level under your special recording conditions. We recommend not to choose too much headroom for this reason.

so we dont want to choose too high of a resistor and raise noise floor.

The lectrosonics claims a wide dynamic range (117 dB), but we have no idea how clean the pres are. so we dont want to put a big resisitor in line (noise) and then add a bunch of preamp gain (more noise).

Knowing that our application is the typical concert environment, max 130 dbA with 50-70 dB of dynamic range at best in a room, what would be a good resistor value? Again on mic in:
Dynamic mic: 300 Ohm impedance, 0.5 mV to 50 mV input level
cmr output level into lowZ input: something less than 0.56V (though CMR manual recommends minimum 5K impedance... i am confused


I asked Bernhard:


Quote from: jerryfreak
Lectrosonics provided me more information on the input impedance for the various inputs. i believe the CMR would be considered a dynamic mic. Do the numbers below help with resistor selection? ideally I want the dynamic range of the mic output to be a match for the recorder, in loud situations (80-130 dBA). I notice on the CMR spec it says max voltage of 0.56V at 2kohm, and 0.9V at 20 kohm. it also says minimum recommended input impedance of 5kohm (much higher than any of the transmitter's inputs). so in this case is the resistance additive? in other words if i add a 4.7K resistor to the mic in, is the effective impedance then 5K ohm?

If i went directly into line-in with impedance of 2.7K, it seems the max voltage of CMR would be slightly above 0.56V ( based on the 0.56V@2kohm, but possibly reduced from this as the mic is only getting 5V input).

I am not so concerned if the levels are very low going into the Lectrosonics unit, as the dynamic range of the Lectrosonics should exceed that of the mic by 30-40 dB

the reason i mentioned reduced output due to 5V input is because apparently the CMR can take 4V-10V, and has lower output at lower voltage, though bernhard couldn't quantify the difference between 4V and 10V when asked (i guess based on the widely varying input impedance of different devices). This is as much as he would say:

Quote from: bernhard
With a 10V supply it will have a higher output capability but will not reach the CMC's value. 4V are the absolute minimum requirements, the maximum output level is significantly lower already under these conditions.

.. no I did not measure it but following the schematics it is obvious. The precise value also depends on the load impedance. So to reach maximum level you should switch the following input to its highest impedance, if possible.

my battery boxes have always run directly off a 9V in the 7-8.5V range. i have no idea if the 5V provided by the lectrosonics circuit above will compromise performance





Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: DSatz on February 05, 2019, 01:02:56 PM
jerryfreak, your post interests me a lot since I would like to consider a similar, possible arrangement for myself some day.

My one observation is that I think 130 dB SPL as a ceiling value is too high. I think you can afford to let more of the signal from the microphones into the recorder's preamps, in other words. 130 dB SPL is typical of a brass instrument such as trombone or trumpet playing at maximum volume, if the microphone is less than a foot away from the instrument's bell--or if a person is totally screaming (or a trained operatic soprano is hitting a high note with full force) directly into a microphone (say 2" distance or less). If you have even a one-meter distance from things like the above, the levels at the microphone won't reach 130 dB SPL.

130 dB SPL on any ongoing basis is so loud that no human being (except one who is already profoundly deaf) would voluntarily stay in the same room with it. It would engage your fight-or-flight mechanism to an almost uncontrollable extent. At ~120 dB SPL, if you're standing next to someone and you want to tell them something, you'd have to yell to be heard. At 130 dB SPL, even if you and the other person could withstand it somehow, you could scream all you wanted, and they still wouldn't hear you.

Does that explain the difference? Being in a 130 dB SPL environment for more than a small number of seconds would be torture, and I don't use that word lightly. Your legs would probably be running for the nearest exit before you even realized they were.

For decades, the overload point of many professional condenser microphones was around 120 dB SPL, and that level is rarely reached in normal recording work. I think the highest level I ever legitimately encountered was a single peak at around 122 dB SPL, which was during a vocal master class. It came from a very strong operatic soprano doing a special exercise that required considerable warmup, followed by a strong attack on a note in the top register; the microphone was six inches in front of her. It slightly overloaded the preamp that I was using at the time, but not the microphone. I think that if I were you in the situation you have, I would go another 6 dB and draw the line at 124. I think that should be more than enough headroom for any semi-distant recording that I might ever do; even that might well be too cautious, to the detriment of quiet recordings.

Note that wind can produce similar levels of output from a condenser microphone capsule as extremely high SPLs, but I assume that you would use windscreening if you were recording outdoors.

--best regards
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on February 06, 2019, 12:36:56 AM
thanks ill be experimenting

i bought a cheap handheld spl meter that may not be absolutely accurate but will be a reference for me to test since im trying to set up both the schoeps and the 4061s

i plan on testing the cmr powered by a regulated power supply at its min and max voltage to get an idea of the difference in output level (and if there is any value in adding additional power when you have a device like the lectro that provides 5V).

basically ill be close-ish mic'ing a monitor at a repeatable, measurable output level. i guess ill experiment with a 5K pot to see what works as far as matching mic input to the recorder. 130 dB was an extreme upper limit, and yes sometimes when stack taping im in places where it is uncomfortably loud (with earplugs). ill prob try to match 120 dBA to -10 dBFS jsut to give myself a little space for transients
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on February 09, 2019, 08:43:04 PM
feels weird updating 2 threads, but i reported my results with testing the CMR+SPDR over in the SPDR thread

http://taperssection.com/index.php?topic=187843.msg2290730#msg2290730
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: DSatz on February 10, 2019, 12:23:35 AM
"A" weighting at 100+ dB SPL is absurd. That curve is designed to mimic the ear's sensitivity at 40 phons, which at 1 kHz is equivalent to 40 dB SPL. Above that level, progressively less and less treble emphasis is needed since the ear/brain become more nearly linear in its/their sensitivity. See https://en.wikipedia.org/wiki/Equal-loudness_contour

--best regards
Title: Re: Schoeps CMR (mshilarious please enter!)
Post by: jerryfreak on July 05, 2019, 10:17:25 PM
update:

did some bench testing of CMR at different voltages. Used a test tone generator to simulate concert volume. Peaks on the recorder (Tascam DR100 mkiii) maxed out around -12dB in at higher input voltages


I tested the CMRs from 3.5V-11.0V input voltage (spec is 4.0V-10V), i was expecting better S/N at higher voltages, heres what i found

-output signal level increases up to 5.5V, then is flat from 5.5-11V

considering this flat output level from 5.5-11V as "0 dB", the following attenuation was observed
5.0V -1.5dB
4.8V -2.5dB
4.6V -3dB
4.4V -4dB
4.2V -5.5dB
4.0V -7dB
3.8V -12.5dB
3.6V -16.5dB
3.5V -19.5dB

So as you can see performance tails off considerably below 5V which is why the SPDR that provides 4.0V under load is a less-than-ideal solution (especially considering what it costs). most decent batterybox solutions provide 7-9V which should work fine

measuring noise (doing my best with loaded mic capsules wrapped up in multiple layers buried in a box in the quietest environment, peaks below -60 dB, rms around -75dB), i could not notice a difference in noise in the 5-10V range. noise was down a bit at 4V, reduced at about the same level as the output signal was attenuated at 4V

I did not test max SPL handling, but assume that performance at 10V would be at least as good as powering at 5.5V, perhaps better