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Author Topic: 3 Wire Box vs. SP BB for SP AT853's  (Read 10283 times)

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Offline scoper

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3 Wire Box vs. SP BB for SP AT853's
« on: February 24, 2006, 03:26:19 PM »
My current rig:
AT853 (SP) > SP BB (with Levels and Bass Rolloff) > AD20 > JB3

My understanding of the 3 wire BB advantage is that it increases the SPL that the 853's can handle, by increasing the power fed to the mics. It also results in a net decrease of gain that would feed the AD20 (some say -6db, some say more).

Since my BB has level controls, I usually attenuate the levels there slightly, so as not to overdrive the pre-amp in the AD20. I usually run the AD20 at either the minimum (+17db) setting, or the 9-10 o'clock setting.

Isn't this the same effect? I've never had a situation where the mics have brickwalled, even at a recent Billy Joel show where the sound (especially bass) was painfully loud.

With the current config, I also have the option of feeding the JB3 directly from the BB in louder shows, if I want to go superstealth. The 3 wire box (per Sanjay) necessitates using the mini-xlr inputs. I also lose the level control and the bass rolloff (I never use the rolloff anyway).

How is the 3 wire box an advantage to me?

TIA,

Scott
AT853U cardioid (low sens mod)| Countryman B3 Omni (low sens mod) > CA-UGLY II > Sony PCM-M10

Former: Sony MiniDisc/JB3/MicroTrack/R-09HR

Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #1 on: February 24, 2006, 05:31:01 PM »
My current rig:
AT853 (SP) > SP BB (with Levels and Bass Rolloff) > AD20 > JB3

My understanding of the 3 wire BB advantage is that it increases the SPL that the 853's can handle, by increasing the power fed to the mics. It also results in a net decrease of gain that would feed the AD20 (some say -6db, some say more).

Since my BB has level controls, I usually attenuate the levels there slightly, so as not to overdrive the pre-amp in the AD20. I usually run the AD20 at either the minimum (+17db) setting, or the 9-10 o'clock setting.

Isn't this the same effect? I've never had a situation where the mics have brickwalled, even at a recent Billy Joel show where the sound (especially bass) was painfully loud.

With the current config, I also have the option of feeding the JB3 directly from the BB in louder shows, if I want to go superstealth. The 3 wire box (per Sanjay) necessitates using the mini-xlr inputs. I also lose the level control and the bass rolloff (I never use the rolloff anyway).

How is the 3 wire box an advantage to me?

TIA,

Scott


You claim that you do not brickwall, but my guess is that you are distorting somewhat even in moderatly loud settings.  You might mitigate that with attenuation and bass rolloff, but the distortion is still there.

There are several places you can distort: at the mics, at the mic input (this is usually called "brickwall"), at the line level, or at the ADC (called "clipping").  All can cause distortion.

You solve "brickwall" by attenuating the mics or running line in instead of mic in.  But mic distortion is still there.  You need "3-wire" power to fix this.  You can acheive 3-wire powering, either with a 3-wire battery box (Sanjay or myself) or using phantom power adapters.

My guess is that once you hear proper mic wiring you will be able to tell the difference.  Those AT853 are really very good sounding mics if they are wired correctly.

Now, maybe your music just isn't loud enough.  Maybe you need to move from Billy Joel to something evil!!!

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline willndmb

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #2 on: February 24, 2006, 06:26:19 PM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do
Mics - AKG ck61/ck63 (c480b & Naiant actives), SP-BMC-2
XLR Cables - Silver Path w/Darktrain stubbies
Interconnect Cables - Dogstar (XLR), Darktrain (RCA > 1/8) (1/8 > 1/8), and Kind Kables (1/8f > 1/4)
Preamps - Naiant Littlebox & Tinybox
Recorders - PCM-M10 & DR-60D

Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #3 on: February 24, 2006, 06:28:27 PM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the differnce...

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline willndmb

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #4 on: February 24, 2006, 06:33:13 PM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the differnce...

  Richard

would the 3 wire replace the sp box all together or is addition too it?
Mics - AKG ck61/ck63 (c480b & Naiant actives), SP-BMC-2
XLR Cables - Silver Path w/Darktrain stubbies
Interconnect Cables - Dogstar (XLR), Darktrain (RCA > 1/8) (1/8 > 1/8), and Kind Kables (1/8f > 1/4)
Preamps - Naiant Littlebox & Tinybox
Recorders - PCM-M10 & DR-60D

Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #5 on: February 24, 2006, 06:43:59 PM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the difference...

  Richard

would the 3 wire replace the sp box all together or is addition too it?

Yes, the three wire box would replace the SP box.  You would have:
  mics > 3-wire-box > pre/adc > NJB3
skip the pre/adc if you do line in.

  Richard

PS:  Hmm.  Perhaps Sanjay or I should put one of these in the gear loaner program.  Although you would need miniXLRs on your mics to be able to use it.

PPS: Note that neither Sanjay nor I are trying to fluff these for our own profit.  We are just addressing a need out there.  In fact, I haven't even sold one yet!  (Though I think Hyperplane may be my first customer.)  And if you want to build one, here is a (simplified) version:

Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Offline scoper

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #6 on: February 24, 2006, 07:50:41 PM »

PPS: Note that neither Sanjay nor I are trying to fluff these for our own profit.  We are just addressing a need out there.  In fact, I haven't even sold one yet!  (Though I think Hyperplane may be my first customer.)  And if you want to build one, here is a (simplified) version:
[img]http://www.cs.uwaterloo.ca/~mannr/AT853/at853_ckt.jpg[/img


I would never accuse you of "fluffing" for profit. I have emailed Sanjay about it (to find out price, before he posted it), and I'm considering. But I don't do a lot of LOUD shows - many of the shows I go to are amplified acoustic music, which is never a problem - I just want maximum flexibility, and to get the best I can out of my equipment.

Scott
AT853U cardioid (low sens mod)| Countryman B3 Omni (low sens mod) > CA-UGLY II > Sony PCM-M10

Former: Sony MiniDisc/JB3/MicroTrack/R-09HR

Offline Zaphod

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #7 on: February 24, 2006, 07:57:06 PM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the differnce...

  Richard


Hey Richard have you done any comps of the AT853s phantom vs. three wire?
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Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #8 on: February 25, 2006, 01:08:31 AM »
i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the differnce...

  Richard


Hey Richard have you done any comps of the AT853s phantom vs. three wire?

Sorry, I don't think I have any comparisons.  In true unscientific fashion I modified my first pair of AT mics the day they arrived from SoundProfessionals!

I guess I *should* be able to do a comparison though.  God knows, I've got enought AT gear!

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #9 on: March 05, 2006, 10:57:39 AM »
We have a new mod that we do to these mics that keeps the mics two wire but reduces the real distortion to 0.5% at 1k at 114db PM me if your interested.

Chris Church


My current rig:
AT853 (SP) > SP BB (with Levels and Bass Rolloff) > AD20 > JB3

My understanding of the 3 wire BB advantage is that it increases the SPL that the 853's can handle, by increasing the power fed to the mics. It also results in a net decrease of gain that would feed the AD20 (some say -6db, some say more).

Since my BB has level controls, I usually attenuate the levels there slightly, so as not to overdrive the pre-amp in the AD20. I usually run the AD20 at either the minimum (+17db) setting, or the 9-10 o'clock setting.

Isn't this the same effect? I've never had a situation where the mics have brickwalled, even at a recent Billy Joel show where the sound (especially bass) was painfully loud.

With the current config, I also have the option of feeding the JB3 directly from the BB in louder shows, if I want to go superstealth. The 3 wire box (per Sanjay) necessitates using the mini-xlr inputs. I also lose the level control and the bass rolloff (I never use the rolloff anyway).

How is the 3 wire box an advantage to me?

TIA,

Scott


Offline scoper

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #10 on: March 05, 2006, 11:27:39 AM »
I've ordered the 3 wire box from Sanjay, and he's also making a reverse connection for me (minxlr to 1/8") so I can use the mics with my old SP battery box (and presumably, without the 7db loss in gain) in low SPL situations. I often record amplified acoustic shows that would never come near the levels which would distort the mics.

Kudos to Chris at SoundProfessionals for letting me pick his brain about this even though there was no revenue benefit to him - he's always been willing and eager to talk about anything audio.

I'll be using the new setup in 2 weeks (Fab Faux at Queens College), and I'll report on the results then.

Scott
AT853U cardioid (low sens mod)| Countryman B3 Omni (low sens mod) > CA-UGLY II > Sony PCM-M10

Former: Sony MiniDisc/JB3/MicroTrack/R-09HR

Offline madman

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #11 on: March 05, 2006, 07:22:19 PM »
I'm surprised that people who run the SP BB with the 853s don't see distortion.  I ran those mics for a short time and only the quietest shows would end up distortion free.  Any loud rock shows would have horrible sounding bass, especially on the kick drum.  I don't see any reason not to go with 3 wire power.  Better safe than sorry with a distorted tape.

Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #12 on: March 05, 2006, 09:33:45 PM »
I've ordered the 3 wire box from Sanjay, and he's also making a reverse connection for me (minxlr to 1/8") so I can use the mics with my old SP battery box (and presumably, without the 7db loss in gain) in low SPL situations. I often record amplified acoustic shows that would never come near the levels which would distort the mics.

Kudos to Chris at SoundProfessionals for letting me pick his brain about this even though there was no revenue benefit to him - he's always been willing and eager to talk about anything audio.

I'll be using the new setup in 2 weeks (Fab Faux at Queens College), and I'll report on the results then.

Scott


Yeah, I've had great experiences with Chris at SP as well.  He's always given me straight answers, eg., about what capsules he uses, etc.  And their work it top notch.  All cables are well soldered, heat shrinked, and drenched in hot melt glue!!

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #13 on: March 11, 2006, 03:20:39 PM »

Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church


i have never had a prob running the same exact set up, even beforei had the ad20 i had no probs

i take that back ONCE when my mics were seriously 5 feet from the stack i had distortion on loud bass
so i too don't understand what having a 3 wire box would do

There is nothing wrong with the regular setup, just that a 3-wire battery box (or phantom power) is an improvement.

Try it and you'll see the difference...

  Richard

would the 3 wire replace the sp box all together or is addition too it?

Yes, the three wire box would replace the SP box.  You would have:
  mics > 3-wire-box > pre/adc > NJB3
skip the pre/adc if you do line in.

  Richard

PS:  Hmm.  Perhaps Sanjay or I should put one of these in the gear loaner program.  Although you would need miniXLRs on your mics to be able to use it.

PPS: Note that neither Sanjay nor I are trying to fluff these for our own profit.  We are just addressing a need out there.  In fact, I haven't even sold one yet!  (Though I think Hyperplane may be my first customer.)  And if you want to build one, here is a (simplified) version:



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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #14 on: March 11, 2006, 04:22:06 PM »

Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church

What's the theory behind that, Chris?
These electret FET circuits are pretty much auto-biasing to a given current, regardless of the source resistor.  Reducing the source resistance should increase the distortion in a source follower circuit, not reduce it.  It would also significantly reduce the overload levels, since the 4.7k would have less than 1V across it.
I'm not saying that you're wrong - I'd just like to understand your thinking :)

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #15 on: March 11, 2006, 06:36:30 PM »
You are correct sorry I was thinking of something else when I was replying to that post.
I do not wire my preamp the same way I use a differnt method with a 4.7k resistor accross the ground and the output of the capsule this reduces distortion a great deal wile only reducing the output by about 4 db and just using a 10k resistor between the + and the capsule bias input. But thats how I do it everyone has there own way. This is part of why my mod works as well as it does. I also have a mod I do to my own cardioid capsules but I do not talk about that one:)


Chris Church

Offline poorlyconditioned

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #16 on: March 12, 2006, 01:21:44 AM »

Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church

What's the theory behind that, Chris?
These electret FET circuits are pretty much auto-biasing to a given current, regardless of the source resistor.  Reducing the source resistance should increase the distortion in a source follower circuit, not reduce it.  It would also significantly reduce the overload levels, since the 4.7k would have less than 1V across it.
I'm not saying that you're wrong - I'd just like to understand your thinking :)

I'm not sure about this, Graeme, but Chris might be talking about running *2 wire* with a 5K source resistor (gain degeneration?) to limit gain/reduce distortion.  I played with this a little bit using the Panasonic (WM60/61) mics.  The idea was to use standard battery box wiring (and also use cheaper headphone cables) and but still reduce the distortion.

But if you're going to use three wires, you might as well use the circuit we have.  My one change was to reduce the source resistor to 13.3k.  This allows me to use the same battery box for both AKG CK91/93 and AT853 caps.  This reduces the headroom for AT853 a bit, but not by much.

Anyway, Chris, can you please confirm the wiring of your *3-wire* box, both the plain box and the preamp version.  I think you could sell the preamp version here.  Several people asked me about mine, but I'm not building them for others...

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #17 on: March 12, 2006, 02:26:12 AM »
I only use mogami three wire lav cable and let me tell you I dont have theory I have tested it with my equipment and there is less distortion with this method I still use three wire cable. For the preamp I use pin 1 ground pin 2 signal pin 3 bias output is 3.5 mm stereo jack.


Chris Church




Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church

What's the theory behind that, Chris?
These electret FET circuits are pretty much auto-biasing to a given current, regardless of the source resistor.  Reducing the source resistance should increase the distortion in a source follower circuit, not reduce it.  It would also significantly reduce the overload levels, since the 4.7k would have less than 1V across it.
I'm not saying that you're wrong - I'd just like to understand your thinking :)

I'm not sure about this, Graeme, but Chris might be talking about running *2 wire* with a 5K source resistor (gain degeneration?) to limit gain/reduce distortion.  I played with this a little bit using the Panasonic (WM60/61) mics.  The idea was to use standard battery box wiring (and also use cheaper headphone cables) and but still reduce the distortion.

But if you're going to use three wires, you might as well use the circuit we have.  My one change was to reduce the source resistor to 13.3k.  This allows me to use the same battery box for both AKG CK91/93 and AT853 caps.  This reduces the headroom for AT853 a bit, but not by much.

Anyway, Chris, can you please confirm the wiring of your *3-wire* box, both the plain box and the preamp version.  I think you could sell the preamp version here.  Several people asked me about mine, but I'm not building them for others...

  Richard


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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #18 on: March 12, 2006, 02:53:12 AM »
I only use mogami three wire lav cable and let me tell you I dont have theory I have tested it with my equipment and there is less distortion with this method I still use three wire cable. For the preamp I use pin 1 ground pin 2 signal pin 3 bias output is 3.5 mm stereo jack.


Chris Church




Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church

What's the theory behind that, Chris?
These electret FET circuits are pretty much auto-biasing to a given current, regardless of the source resistor.  Reducing the source resistance should increase the distortion in a source follower circuit, not reduce it.  It would also significantly reduce the overload levels, since the 4.7k would have less than 1V across it.
I'm not saying that you're wrong - I'd just like to understand your thinking :)

I'm not sure about this, Graeme, but Chris might be talking about running *2 wire* with a 5K source resistor (gain degeneration?) to limit gain/reduce distortion.  I played with this a little bit using the Panasonic (WM60/61) mics.  The idea was to use standard battery box wiring (and also use cheaper headphone cables) and but still reduce the distortion.

But if you're going to use three wires, you might as well use the circuit we have.  My one change was to reduce the source resistor to 13.3k.  This allows me to use the same battery box for both AKG CK91/93 and AT853 caps.  This reduces the headroom for AT853 a bit, but not by much.

Anyway, Chris, can you please confirm the wiring of your *3-wire* box, both the plain box and the preamp version.  I think you could sell the preamp version here.  Several people asked me about mine, but I'm not building them for others...

  Richard


Oh yeah, this just occured to me.  Of course 5K is correct.  The resistance depends on the current draw of the mics.  If you put a voltmeter between the audio and ground pin (ie., across the 5k or whatever resistor), you should see approx. 4 to 5 volts, ie., half the battery voltage.  The source resistor depends on the mics.  30K for AT853, 10-15K for AKG CK91/93, and perhaps 5K for your mics...

So, let me understand this:
- for your mics you use a 3.5mm plug *for each mic*, right?
- for your preamp/ battery box you use two mini XLRM panel mount jacks, right?

(Please forgive me if this is written down on your webpage or elsewhere.)

Anyway, good luck with the gear loan.  Hopefully we'll hear some smokin' tapes out of this!

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #19 on: March 12, 2006, 02:59:39 AM »
5K Works with AT 853 mics too I have measured the distortion. its much less with 4.7 k resistor. I tryed 10k 2k 15k and 4.7k was perfect.


I only use mogami three wire lav cable and let me tell you I dont have theory I have tested it with my equipment and there is less distortion with this method I still use three wire cable. For the preamp I use pin 1 ground pin 2 signal pin 3 bias output is 3.5 mm stereo jack.


Chris Church




Replace that 27k with a 4.7 k resistor and watch what happens distortion goes way down levels are not reduced as much.

Chris Church

What's the theory behind that, Chris?
These electret FET circuits are pretty much auto-biasing to a given current, regardless of the source resistor.  Reducing the source resistance should increase the distortion in a source follower circuit, not reduce it.  It would also significantly reduce the overload levels, since the 4.7k would have less than 1V across it.
I'm not saying that you're wrong - I'd just like to understand your thinking :)

I'm not sure about this, Graeme, but Chris might be talking about running *2 wire* with a 5K source resistor (gain degeneration?) to limit gain/reduce distortion.  I played with this a little bit using the Panasonic (WM60/61) mics.  The idea was to use standard battery box wiring (and also use cheaper headphone cables) and but still reduce the distortion.

But if you're going to use three wires, you might as well use the circuit we have.  My one change was to reduce the source resistor to 13.3k.  This allows me to use the same battery box for both AKG CK91/93 and AT853 caps.  This reduces the headroom for AT853 a bit, but not by much.

Anyway, Chris, can you please confirm the wiring of your *3-wire* box, both the plain box and the preamp version.  I think you could sell the preamp version here.  Several people asked me about mine, but I'm not building them for others...

  Richard


Oh yeah, this just occured to me.  Of course 5K is correct.  The resistance depends on the current draw of the mics.  If you put a voltmeter between the audio and ground pin (ie., across the 5k or whatever resistor), you should see approx. 4 to 5 volts, ie., half the battery voltage.  The source resistor depends on the mics.  30K for AT853, 10-15K for AKG CK91/93, and perhaps 5K for your mics...

So, let me understand this:
- for your mics you use a 3.5mm plug *for each mic*, right?
- for your preamp/ battery box you use two mini XLRM panel mount jacks, right?

(Please forgive me if this is written down on your webpage or elsewhere.)

Anyway, good luck with the gear loan.  Hopefully we'll hear some smokin' tapes out of this!

  Richard


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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #20 on: March 13, 2006, 04:22:38 PM »
Out of curiosity, how does one measure distortion?
Mics: Audix m1290's, AT943's (w/ AT853 C/O/H caps), AT853's
Power: PS-2, Homebrew 3wbb, SPSB-6
Pre/AD: UA-5 (BM2p+), CA-9100, AD-20
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #21 on: March 13, 2006, 04:51:12 PM »

OK so, sorry for a thread hijack...

I've been following the "3 wire vs." thread for a little while.
I've also seen Sanjay's box for sale in the yard, (which is nice cause my cables terminate in the mini xlr's)
would love to have a box for stealthing, but have a question or two.

I have the first pair of Franken Naks Marc Kim sold. DAMN do I Love em!
These are 10v electrets that run on P48 via the AT P48>9v module.

My questions:
there's discussion about what resistors sound best in the box for the at853's..
how could i determine which are best for the Franken Naks?

And once I have that info, who would be willing to accept commission to build me a 3 wire Nak box?


Cheers!
-Mike




hope this schematic helps...
« Last Edit: March 13, 2006, 04:57:26 PM by Big Muff »
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #22 on: March 13, 2006, 06:11:28 PM »

OK so, sorry for a thread hijack...

I've been following the "3 wire vs." thread for a little while.
I've also seen Sanjay's box for sale in the yard, (which is nice cause my cables terminate in the mini xlr's)
would love to have a box for stealthing, but have a question or two.

I have the first pair of Franken Naks Marc Kim sold. DAMN do I Love em!
These are 10v electrets that run on P48 via the AT P48>9v module.

My questions:
there's discussion about what resistors sound best in the box for the at853's..
how could i determine which are best for the Franken Naks?

And once I have that info, who would be willing to accept commission to build me a 3 wire Nak box?


Cheers!
-Mike




hope this schematic helps...


Well, your answer is right there in the schematics!  1.2k.

Measure the voltage across that resitor.  I should be roughly 1/2 the supply voltage, ie., 4.5V.  Try different values until you get it right.  1.2k sounds a bit low, maybe 4.7k or 10k?

  Richard
Mics: Sennheiser MKE2002 (dummy head), Studio Projects C4, AT825 (unmodded), AT822 franken mic (x2), AT853(hc,c,sc,o), Senn. MKE2, Senn MKE40, Shure MX183/5, CA Cards, homebrew Panasonic and Transsound capsules.
Pre/ADC: Presonus Firepod & Firebox, DMIC20(x2), UA5(poorly-modded, AD8620+AD8512opamps), VX440
Recorders: Edirol R4, R09, IBM X24 laptop, NJB3(x2), HiMD(x2), MD(1).
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #23 on: March 13, 2006, 06:57:54 PM »
try a 4.7 insted of the 1.2k make sure its metal film no CARBON! if you see and carbon resistors most often they are 5% gold band or 10% silver band cut it out and remove it and replace all resistors with metal film 1% I like dale resistors they are sparky. Its what I use on all of my preamps.


OK so, sorry for a thread hijack...

I've been following the "3 wire vs." thread for a little while.
I've also seen Sanjay's box for sale in the yard, (which is nice cause my cables terminate in the mini xlr's)
would love to have a box for stealthing, but have a question or two.

I have the first pair of Franken Naks Marc Kim sold. DAMN do I Love em!
These are 10v electrets that run on P48 via the AT P48>9v module.

My questions:
there's discussion about what resistors sound best in the box for the at853's..
how could i determine which are best for the Franken Naks?

And once I have that info, who would be willing to accept commission to build me a 3 wire Nak box?


Cheers!
-Mike




hope this schematic helps...


Well, your answer is right there in the schematics!  1.2k.

Measure the voltage across that resitor.  I should be roughly 1/2 the supply voltage, ie., 4.5V.  Try different values until you get it right.  1.2k sounds a bit low, maybe 4.7k or 10k?

  Richard


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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #24 on: March 13, 2006, 11:04:36 PM »

Thanks guys,

But now that raises more questions.. I know, I'm an electronics noob.

Why would Nakamichi or Primo put in the 1.2k in the first place?
Also, if i were to have it switched out to something higher like the 4.7k metal film what kind of results could i expect?
Assuming this were done, i expect the 3 wire box would require the same 4.7k to produce the best sound, no?

Thanks again,
cheers!
-Mike

 

try a 4.7 insted of the 1.2k make sure its metal film no CARBON! if you see and carbon resistors most often they are 5% gold band or 10% silver band cut it out and remove it and replace all resistors with metal film 1% I like dale resistors they are sparky. Its what I use on all of my preamps.




Well, your answer is right there in the schematics!  1.2k.

Measure the voltage across that resitor.  I should be roughly 1/2 the supply voltage, ie., 4.5V.  Try different values until you get it right.  1.2k sounds a bit low, maybe 4.7k or 10k?

  Richard

[/quote]
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #25 on: March 14, 2006, 02:02:32 AM »
Quote
My current rig:
AT853 (SP) > SP BB (with Levels and Bass Rolloff) > AD20 > JB3

please forgive my ignorance, but what is the purpose of the AD20? I realize that it's a analog-digital converter, but doesn't the JB3 do that already?

thanks for all of your patience.

Brett
SP-CMC2 --> SP-SPSB1 --> JB3

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #26 on: March 14, 2006, 11:18:32 AM »
Hi I measure distortion using a earthworks m50 mic as a reference point. I use a dupont calibrator with two levels one at 96db and one at 114db at 1k. This unit puts out a sine wave that is very clean and almost distortion free it has a distortion of less then 0.003% at 114db. Its a basic decibel meter calibrator that has a coupler at the end of it to 1/2 inch, I further reduce this for my omni mics to 6mm via a rubber washer. This gives me a known source for a simple distortion measurement. I then use WINAUDIOMLS to tell me the THD and THD+NOISE. I remove the known distortion of 0.003% and add the resalt of the test. From my mics, I also use this method to match my capsules for level. I base level on 1k I find that it is very accurate. Some people would argue that point but I feel that it gets me very close. I also do a broad band freq resp measurment to tell me what the mic does in level from 20hz to 90k then I match them again. it takes a while to do this then I put the matched capsules in groups of two in a static bag until I sell them. You can do the same test at home by using a computer speaker and a decibel meter both capsules have to be placed in the same exact spot in order to make the measurment good. I use a little stand i made with a aligator clip to hold the wire to the capsule and I bolt the stand to one of our workbenches So that it does not move during our freq resp test. This is how we do it there are much better ways but they cost alot more money to do. We do try to be very scientific with our tests. Using a lab calibrated source for measurments helps. At the end of the day you still have to use your ears because in the end you dont have a computer listing to the sound you have your ears and if they are trained to know what to listen for, they are the most powerfull audio analyizer in the world.


Chris Church
 


Out of curiosity, how does one measure distortion?

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #27 on: March 14, 2006, 11:42:07 AM »
Quote
My current rig:
AT853 (SP) > SP BB (with Levels and Bass Rolloff) > AD20 > JB3

please forgive my ignorance, but what is the purpose of the AD20? I realize that it's a analog-digital converter, but doesn't the JB3 do that already?

thanks for all of your patience.

Brett

General thought is that the ADC in many consumer level devices is a weak spot. I don't think the ADC in the jb3 is that awful, but I noticed a substantial improvement when I used the AD20 with a MiniDisc recorder.

The AD-20  is also a preamp, with a range of +17 to +45 db. At the higher reaches it is extremely noisy, though. Anything needing more than +31db gain at the show, I set it  to +31 and add the rest in post.

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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #28 on: March 14, 2006, 12:56:03 PM »
thanks scoper... one more question if you don't mind... so the a->d steps are the reading of the analog input and the conversion to a digital (1 and 0) pattern. are you saying that some devices aren't able to correctly read the analog input and therefore 'miscreate' a correct conversion?
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #29 on: March 14, 2006, 01:57:03 PM »
thanks scoper... one more question if you don't mind... so the a->d steps are the reading of the analog input and the conversion to a digital (1 and 0) pattern. are you saying that some devices aren't able to correctly read the analog input and therefore 'miscreate' a correct conversion?

I'm sure someone here can give a better answer to this than me...

Yes, the A/D circuit is responsible for turning analog music into 1's and 0's. There are expensive boxes with very sophisticated circuitry that do this job. Now try to miniaturize that into a small circuit which can be included into a low priced consumer unit. It's the hardest part to do really well, I guess. Size and cost are the bottlenecks.

Some consumer/pro recording units are known for good ADC sections - the Edirol r-1 and r-4 (still available), the Sony PCM-M1 and TCD-D100 DAT recorders (discontinued). These are all in the $700+ range. The Sound Devices 700 series runs into the thousands. People like the Oade Brothers make a good living modifying circuits on some of these.

You can't expect a $300+/- unit to compete.

Others with more experience, please expand, correct, and clarify - I'm in over my head here.

Scott
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Re: 3 Wire Box vs. SP BB for SP AT853's
« Reply #30 on: March 14, 2006, 03:23:36 PM »
Well its like this there are two parts to a good converted the analog side and the digital side both or just one can be bottle necks in the circuit.
Meaning that you can have a great converter and a noisy front end. This means that the best converter in the world would be useless to improve on the sound quality and noise floor. The size of a converter is not a part of the problem as most converters are small in size. Its about keeping a good clock rate and the way in witch they quantize the signal meaning slice it up and convert it into 1's and 0's this is where the real science lies. companies like Apoge have made there name with knowing how to quantize a signal in a musical way.


thanks scoper... one more question if you don't mind... so the a->d steps are the reading of the analog input and the conversion to a digital (1 and 0) pattern. are you saying that some devices aren't able to correctly read the analog input and therefore 'miscreate' a correct conversion?

I'm sure someone here can give a better answer to this than me...

Yes, the A/D circuit is responsible for turning analog music into 1's and 0's. There are expensive boxes with very sophisticated circuitry that do this job. Now try to miniaturize that into a small circuit which can be included into a low priced consumer unit. It's the hardest part to do really well, I guess. Size and cost are the bottlenecks.

Some consumer/pro recording units are known for good ADC sections - the Edirol r-1 and r-4 (still available), the Sony PCM-M1 and TCD-D100 DAT recorders (discontinued). These are all in the $700+ range. The Sound Devices 700 series runs into the thousands. People like the Oade Brothers make a good living modifying circuits on some of these.

You can't expect a $300+/- unit to compete.

Others with more experience, please expand, correct, and clarify - I'm in over my head here.

Scott


 

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