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Author Topic: Trade offs of using active cables?  (Read 2502 times)

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Offline ArchivalAudio

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Re: Trade offs of using active cables?
« Reply #15 on: April 10, 2018, 03:28:37 PM »
Also the 60V version can be ran with a lower phantom power voltage (down to 16V) instead of the standard 48V, so that could save some battery life.

So can the other one.  I dId it all the time with my psp2 at the 12v setting since batteries last alot longer.  Note that this difference is bc of powering the mics at 12v phantom vs 48v phantom, not bc of the lower power draw of the 48v pfa.
My understanding from email conversations with Jon is that without the 60v polarization (aka 60v power) caps like scheopes Milab and a couple of others can not be run at their proper voltage. My Milab vm44's run at 55 or 6o v if I remember. Without the proper voltage for the caps Signal to Noise ratio is affected and SPL handling is greatly diminished. If you have questions about PFA's I'd seek answered in some of those threads or  ask Jon directly via email. I'll just say that some capsules require 60v dc not the 48 of normal phantom. Yes the extended barrels are longer but ill provide the correct voltage, and have more sheilding for better RF rejection. If you don't want or need PFA's don't get them, though they do work and tons of folks are using them for many different "active" capsule configurations.
~ Archival Audio ~
Archiving Worthy Music
since 1986 & digitally since 1995

https://www.facebook.com/ArchivalAudio/

Main Mics: Milab VM-44 Links • Milab DC-196's (Matched  Pair)  • Line Audio CM3's
PreAmps:  Naiant LittleBox • Naiant [Milab VM44] TinyBox • Naiant PIPsqueak
Recorders: MixPre 10T •  Tascam DR-100 mkIII • Sony M-10 

macMini 3Ghz i7 16GB Ram 500GB SSD • MOTU UltraLite
Naiant MSH-2's •   TOA K1's • Beyer TG 153c's •  AT 853 (4.7kmod darktrain) • Countryman B3's (1 k mod)  + other assorted mics

Offline fanofjam

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Re: Trade offs of using active cables?
« Reply #16 on: April 10, 2018, 08:47:29 PM »
Also the 60V version can be ran with a lower phantom power voltage (down to 16V) instead of the standard 48V, so that could save some battery life.

So can the other one.  I dId it all the time with my psp2 at the 12v setting since batteries last alot longer.  Note that this difference is bc of powering the mics at 12v phantom vs 48v phantom, not bc of the lower power draw of the 48v pfa.
My understanding from email conversations with Jon is that without the 60v polarization (aka 60v power) caps like scheopes Milab and a couple of others can not be run at their proper voltage. My Milab vm44's run at 55 or 6o v if I remember. Without the proper voltage for the caps Signal to Noise ratio is affected and SPL handling is greatly diminished. If you have questions about PFA's I'd seek answered in some of those threads or  ask Jon directly via email. I'll just say that some capsules require 60v dc not the 48 of normal phantom. Yes the extended barrels are longer but ill provide the correct voltage, and have more sheilding for better RF rejection. If you don't want or need PFA's don't get them, though they do work and tons of folks are using them for many different "active" capsule configurations.

ArchivalAudio.  Jon at Naiant sells two PFA products.  The first one (I'll call it first generation because he sold it for several years before he came out with the 'long barrel' version) delivers a lower polarization voltage and has a short barrel...actually it's a normal sized XLR connector.  Many people used this one successfully for several years, upon which Jon released a second PFA product.  This is the one that provides 60V polarization voltage and has the longer barrel with better RF rejection.  As far as I know, Jon still sells both products.

Since the release of the later product, there has been much discussion that the second product is 'better' than the first.  This is IMHO incorrect.  Different does not necessarily mean better.  Both products have their pros and cons.  Everyone needs to know what those are in order to best assess which of the two products meets their needs.  I've made this point alot on this product in the past.  For example, if you have non-RF protected components in your chain, which I'm sure many of us do, what good does an RF protected barrel provide?  Are all your cables balanced?  Another example, many people record in situations where they have little headroom to peaking and have to use mic attenuators.  In that case, it might be advantageous to use the first generation PFA which gives a couple of additional db of headroom. 

The reason I point this out is that there's also a misconception that 60V polarization is the 'correct' polarization voltage.  Schoeps mic capsules operate just fine at polarization voltage much lower than 60v.  The characterization that the SPL handling and SNR are 'greatly diminished' is an over-exaggeration. 

This was discussed in great detail maybe five years ago directly with Schoeps when the CMR was being discussed...the CMR does not provide 60V to the capsule although I can't remember what it does provide...seems like it was something around 36v but my memory on that is bad. 

Anyway according to Schoeps, the CMR reduced polarization voltage results in zero effect in frequency response and a reduction in mic sensitivity by a couple of db.  That will naturally result is a slight degradation of the SNR...that's basic math because the mic sensitivity goes down a couple of db, so the ratio is very slightly worse.  As far as SPL, same thing...a slight reduction of peak SPL.  But the key point here is that Schoeps is fine with putting out the CMR, so there's absolutely nothing wrong or incorrect with the PFA version that also provides less than 60V polarization voltage.

As far as the part of your comment that I've bolded, I'm not sure what this means.  Phantom voltage and polarization voltage are two different things...the phantom voltage is stepped up inside of the mic body to provide capsule polarization voltage.  For example, the CMC6 mic body can be powered with either 12V or 48V phantom power and the capsule still receives the same polarization voltage.
« Last Edit: April 10, 2018, 09:00:21 PM by fanofjam »

Offline noahbickart

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Re: Trade offs of using active cables?
« Reply #17 on: April 10, 2018, 08:50:46 PM »
I have one set of the older PFA and one of the newer. There is only one practical difference. The older pfa requires a few more db of gain. They sound the same and neither is "better" than the other.
Recording:
Capsules: Schoeps mk41v (x2), mk4v (x2), mk22 (x2), mk3 (x2), mk21 & mk8
Cables: 2x nbob KCY, 1 pair nbob actives, Darktrain 2 and 4 channel KCY extensions:
Preamps:    Schoeps VMS 02iub, Naiant Littlebox, Naiant IPA, Sound Devices Mixpre6
Recorders: Sound Devices Mixpre6, Sony PCM m10

Home Playback: Mytek DSD 192> McIntosh MC162> Eminent Tech LFT-16; Musical Fidelity xCan v2> Hifiman HE-4XX / Beyerdynamic DT880

Office Playback: Grace m903> AKG k701 / Hifiman HE-400

Offline MBHOTAPER

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Re: Trade offs of using active cables?
« Reply #18 on: April 11, 2018, 02:32:18 AM »
I'm saving to get a set of active cables with PFA's for use with Schoeps mk4's and wonder if anyone has info on what, if any, downsides there are to going this route?

I imagine there might be more susceptibility to rf and other interference, as I think the actives are unbalanced.

Would this be more or less of an issue when recording loud rock shows?

Anything else to consider when deciding whether to use actives or not?

Many thanks,
Chris
For me actives = low profile thus less likely to receive complaints on blocking views. I prefer the ipa over the pfa for stealth and the available gain settings (line in instead of mic in on deck).

Offline DSatz

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Re: Trade offs of using active cables?
« Reply #19 on: April 11, 2018, 06:41:51 AM »
fanofjam, a microphone's maximum SPL doesn't decrease if its capsule's polarization voltage is reduced. On the contrary, the maximum SPL increases by an amount corresponding to the reduction in sensitivity. Maximum SPL is determined by the voltage limit (clipping point) of the amplifier's first stage. When the polarization voltage decreases, so does the voltage applied to that first stage for any given SPL.

This situation illustrates the difference between dynamic range and signal-to-noise ratio. The overall dynamic range of the microphone is about the same regardless of polarization voltage. But the signal-to-noise ratio is greater when that voltage is higher, since the noise output of the amplifier's first stage is essentially constant while the signal output of the capsule is proportional to its polarization voltage. Signal-to-noise ratio is generally the more important issue in practice; that's why God gave us mike preamps and recorder inputs with variable gain.

--best regards
« Last Edit: April 11, 2018, 08:59:52 AM by DSatz »
music > microphones > a recorder of some sort

Offline fanofjam

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Re: Trade offs of using active cables?
« Reply #20 on: April 11, 2018, 02:31:35 PM »
fanofjam, a microphone's maximum SPL doesn't decrease if its capsule's polarization voltage is reduced. On the contrary, the maximum SPL increases by an amount corresponding to the reduction in sensitivity. Maximum SPL is determined by the voltage limit (clipping point) of the amplifier's first stage. When the polarization voltage decreases, so does the voltage applied to that first stage for any given SPL.

This situation illustrates the difference between dynamic range and signal-to-noise ratio. The overall dynamic range of the microphone is about the same regardless of polarization voltage. But the signal-to-noise ratio is greater when that voltage is higher, since the noise output of the amplifier's first stage is essentially constant while the signal output of the capsule is proportional to its polarization voltage. Signal-to-noise ratio is generally the more important issue in practice; that's why God gave us mike preamps and recorder inputs with variable gain.

--best regards

Thanks for the clarification DSatz.  My degree is mechanical engineering, so I like the tech explanations and knowing how stuff works.  I think I drive my wife's doctors crazy bc I'm always asking about the tests they run and the gadgets they use.  It's fascinating.  Ive had to explain that its just my curiosity so they don't think my motivation is that I'm checking up on them.  Doctors generally don't like patients that second guess or challenge them.  Lol.

Offline ArchivalAudio

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Re: Trade offs of using active cables?
« Reply #21 on: April 12, 2018, 01:56:30 AM »
I'll just say that some capsules require 60v dc not the 48 of normal phantom.
As far as the part of your comment that I've bolded, I'm not sure what this means.  Phantom voltage and polarization voltage are two different things...the phantom voltage is stepped up inside of the mic body to provide capsule polarization voltage. 

I appreciate everyone's comments and keep trying to learn more, so thank you.

I'm no engineer... and most technical stuff goes over my head - I am not a scheopes guy and don't know crap about them --- only what I read here and there... in June of 2014 I received an email from Jon from tests on my Milab VM 44's (which he had for about 6 months) my understanding was that  while the bodies of my milab VM44 links can be powered anywhere from 16 to 48v phantom, the actual capsule voltage is stepped up to 60v dc (this was the polarization I spoke to), and I thought that some of the schoepes capsules  function in a similar way and thus the "second" version or "product"  of the PFA's you mention were born  to supply the proper 60v dc voltage for certain capsules.
his test results on the Milab VM 44's he tested (Milab used a 5 pin  connector and cable). this was so he could to produce a TinyBox for the VM44s he stated:
Quote
Here are my results of testing:

pin configuration is:

1 +60V (pad switches to +14V)
2  signal -
3 signal +
4 ground
5 +6.2V
as I understand this was the voltage  that was leaving the bodies to ward the capsules. The original 48v phantom was stepped up to offer the proper operating voltage.  the voltage circuit in the PFA's did at some point become  a version 2 (or higher) to enable supplying a stepped up voltage from 48 to 60v and as I read  it was in-part to help supply the correct voltage for certain versions of schoepes caps.  That's my layman term of understanding. the bottom line is that ether version of the PFA may work fine though there was a reason  for the updated circuit design. I have a tinyBox that poweres my Milab vm44 capsules and acts as a mic premap, and I have subsequently gotten the extended barrel PFA's to a Y cable with a TinyBox or
Quote
2 PFA’s right and left to a Y cable with the 6-pin mini XLR. (tinybox plug)Extended stereo with polarization
they work great and also have a 15' 6-pin to 6-pin single mogami extension cable that I can run between the  Y cables  giving me  the standard ~10" of Milab cable  + 3' of Y  + 15' of Naiant cable to my  PFA's  (or about + 28' of cable) which is sweet way to run them onstage with a very low profile to keep my gear off to one side or back at the house mix position.

~ Archival Audio ~
Archiving Worthy Music
since 1986 & digitally since 1995

https://www.facebook.com/ArchivalAudio/

Main Mics: Milab VM-44 Links • Milab DC-196's (Matched  Pair)  • Line Audio CM3's
PreAmps:  Naiant LittleBox • Naiant [Milab VM44] TinyBox • Naiant PIPsqueak
Recorders: MixPre 10T •  Tascam DR-100 mkIII • Sony M-10 

macMini 3Ghz i7 16GB Ram 500GB SSD • MOTU UltraLite
Naiant MSH-2's •   TOA K1's • Beyer TG 153c's •  AT 853 (4.7kmod darktrain) • Countryman B3's (1 k mod)  + other assorted mics

Offline DSatz

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Re: Trade offs of using active cables?
« Reply #22 on: April 12, 2018, 09:06:41 AM »
ArchivalAudio, it depends on the microphone. 48-Volt phantom power is delivered through a matched pair of 6.8 kOhm resistors--so the more current a mike draws, the lower the actual DC voltage will be on the cable or at the microphone. In older phantom-powered designs (e.g. Neumann fet 80 series microphones such as the KM 84 and U 87), the supply current was < 1 mA, so the DC voltage actually delivered to the microphone was still in the 40s--high enough for that voltage to be simply filtered and applied to the capsule to polarize it. This arrangement didn't achieve the final dB or two of signal-to-noise performance, but the advantages of simpler powering and cabling and solid-state reliability were greatly preferred over tubes by most engineers.

Since the 1970s it has been more common for new designs to use DC converters as you described, where the DC supply voltage drives an RF oscillator (i.e. it is converted to AC at a frequency above the human hearing range) and then stepped up to a higher voltage, rectified back to DC and used to polarize the capsule, commonly at ca. 60 Volts. However, this (along with the lower noise and increased sensitivity and maximum SPL expected by then) demanded more supply current. This, in turn, because of the 6.8 kOhm resistors, meant that the incoming DC voltage at the microphone was distinctly lower, commonly in the 30s. So "in for a penny, in for a pound"--there was a definite generational difference between the kind of amplifier electronics seen in P48 designs from the late 1960s and those from the mid-70s and onwards.

Historically the two leaders in this respect were AKG with the original C 451 (not the present-day electret "tribute" microphone of the same name), which drew 6 mA at 48 Volts, and the Schoeps "Colette" (CMC 50) series, which drew about 4.5 mA. For years the DIN/IEC standard set a limit of 2 mA per microphone for 48-Volt phantom powering, and even after that standard was finally revised, there were real problems using these higher-current microphones with older mixers and recorders that didn't have enough current available from their phantom powering circuits. Both manufacturers were forced to offer alternative models that drew less current (AKG C 452, Schoeps CMT 50 series).

--best regards
« Last Edit: April 12, 2018, 09:16:05 AM by DSatz »
music > microphones > a recorder of some sort

Offline ArchivalAudio

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Re: Trade offs of using active cables?
« Reply #23 on: April 12, 2018, 03:47:39 PM »
 DSatz Thanks for your reply ^^^^ up there. I think it helps to clarify some thoughts, at least for me. bravo.
~ Archival Audio ~
Archiving Worthy Music
since 1986 & digitally since 1995

https://www.facebook.com/ArchivalAudio/

Main Mics: Milab VM-44 Links • Milab DC-196's (Matched  Pair)  • Line Audio CM3's
PreAmps:  Naiant LittleBox • Naiant [Milab VM44] TinyBox • Naiant PIPsqueak
Recorders: MixPre 10T •  Tascam DR-100 mkIII • Sony M-10 

macMini 3Ghz i7 16GB Ram 500GB SSD • MOTU UltraLite
Naiant MSH-2's •   TOA K1's • Beyer TG 153c's •  AT 853 (4.7kmod darktrain) • Countryman B3's (1 k mod)  + other assorted mics

Offline checht

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Re: Trade offs of using active cables?
« Reply #24 on: April 12, 2018, 04:20:59 PM »
Wow. This has turned into an hugely informative thread. Many thanks to all for the great questions and answers.

To bring things full circle, way back in the mid 80's, when I switched to KM84i's from dynamic mics, I built a box with six 9v batts in series (54v) plus Jensen transformers to decouple. (Yes, I know there was an impedance mismatch, and I should have included some active circuitry). The Jensen had a bit of gain from how it was wound, so I could go line in to my D-5 and then PCM F-1. Compared to the spendy Neuman battery boxes plus Tandy decouplers everyone was using at the time, the box was pretty awesome. I ended up making & selling many of them, and shared the design with Doug Oade, who added active circuitry and developed his line of batt boxes and pre's.

These days, I'm grateful for others who are making killer gear for us; hard to solder with poor vision  :)

~Chris
« Last Edit: April 13, 2018, 11:14:04 AM by checht »
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Offline ArchivalAudio

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Re: Trade offs of using active cables?
« Reply #25 on: April 19, 2018, 01:38:43 PM »
Wow. This has turned into an hugely informative thread. Many thanks to all for the great questions and answers.

To bring things full circle, way back in the mid 80's, when I switched to KM84i's from dynamic mics, I built a box with six 9v batts in series (54v) plus Jensen transformers to decouple. (Yes, I know there was an impedance mismatch, and I should have included some active circuitry). The Jensen had a bit of gain from how it was wound, so I could go line in to my D-5 and then PCM F-1. Compared to the spendy Neuman battery boxes plus Tandy decouplers everyone was using at the time, the box was pretty awesome. I ended up making & selling many of them, and shared the design with Doug Oade, who added active circuitry and developed his line of batt boxes and pre's.

These days, I'm grateful for others who are making killer gear for us; hard to solder with poor vision  :)

~Chris
Chris,
That is a wonderful piece of taper history, and to think the Oades owe their box success to you! that's awesome! thanks. --Ian
~ Archival Audio ~
Archiving Worthy Music
since 1986 & digitally since 1995

https://www.facebook.com/ArchivalAudio/

Main Mics: Milab VM-44 Links • Milab DC-196's (Matched  Pair)  • Line Audio CM3's
PreAmps:  Naiant LittleBox • Naiant [Milab VM44] TinyBox • Naiant PIPsqueak
Recorders: MixPre 10T •  Tascam DR-100 mkIII • Sony M-10 

macMini 3Ghz i7 16GB Ram 500GB SSD • MOTU UltraLite
Naiant MSH-2's •   TOA K1's • Beyer TG 153c's •  AT 853 (4.7kmod darktrain) • Countryman B3's (1 k mod)  + other assorted mics

Offline rocksuitcase

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Re: Trade offs of using active cables?
« Reply #26 on: April 19, 2018, 02:00:05 PM »
Wow. This has turned into an hugely informative thread. Many thanks to all for the great questions and answers.

To bring things full circle, way back in the mid 80's, when I switched to KM84i's from dynamic mics, I built a box with six 9v batts in series (54v) plus Jensen transformers to decouple. (Yes, I know there was an impedance mismatch, and I should have included some active circuitry). The Jensen had a bit of gain from how it was wound, so I could go line in to my D-5 and then PCM F-1. Compared to the spendy Neuman battery boxes plus Tandy decouplers everyone was using at the time, the box was pretty awesome. I ended up making & selling many of them, and shared the design with Doug Oade, who added active circuitry and developed his line of batt boxes and pre's.

These days, I'm grateful for others who are making killer gear for us; hard to solder with poor vision  :)

~Chris
Chris,
That is a wonderful piece of taper history, and to think the Oades owe their box success to you! that's awesome! thanks. --Ian
I've been meaning to add to Chris' story. My college buddy who did taught me about electronics built a Jensen transformer box like yours after discussing it with Doug Oade when we had one of our crew buy an AKG C422 and were having major issues getting a decent signal into a D5. It would be unable to move above 1 and still distort (of course). So, we had the Oade's mod the Pre-amps on 2 of our D5's and then Doug told Yac how to build the Jensen box. This was spring 1985, not sure if Doug had gotten your design by then or not, but what you describe is very similar to how our DIY one turned out. I've been looking but cannot find a picture of the one Yac built. From that point forward, the 422 made great tapes, then pre-amps got "better" on portable decks. Sure wish I knew where that 422 wound up!
music IS love

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Offline checht

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Re: Trade offs of using active cables?
« Reply #27 on: April 19, 2018, 02:23:25 PM »
So cool to get the pieces of the story into place. Great to know that we dinosaurs are not extinct yet.

I built my first Jensen box at college in 1983, right when I got Neumanns. To be clear I was a tinkerer, not an engineer like Doug, who made gear rhae far eclipsed my designs.

I was motivated by wanting something cheaper and smaller than the Neumann boxes, and better sounding than Radio Shack's finest. I thought Neve consoles sounded awesomw, so called them. got an engineer, and asked where they got their transformers. Then I called Jensen and asked if they had anything with gain. Very lucky that kind enfineers took pity on my ignorance and helped me out!

Next topic: stealthing with PCM F-1, Betamax, and huge batteries.  :banging head:
Schoeps MSTC64g, Shure MV-88
Schoeps KCY 250/0 lg, Naiant IPA, PFA 60v
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Offline rocksuitcase

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Re: Trade offs of using active cables?
« Reply #28 on: April 19, 2018, 02:46:54 PM »
So cool to get the pieces of the story into place. Great to know that we dinosaurs are not extinct yet.

Next topic: stealthing with PCM F-1, Betamax, and huge batteries.  :banging head:
See also, GD Las Vegas 3-26-1983. there was at least two "stealth PCMF-1 rigs" in the building. lol
music IS love

When you get confused, listen to the music play!

Mics:         AKG460|CK61|CK1|CK3|CK8|Beyer M 201E
Recorders:Marantz PMD661 OADE Concert mod; Tascam DR680 MKI

 

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