Is External Phantom power better than In-The-Pre-Power?

Amplove · 15th September 2005

Is External Phantom power better than In-The-Pre-Power?

So sometimes I can't patch a mic that needs phantom power through my snake (which goes straight to the patchbay) and then patch to my pre. The only way it'll work is if I bypass the patchbay and plug straight into the back of the pre (which is a pain with a big rack and all. Then I read some things (not very detailed) with people mentioning that internal phantom power degrades the sound. Is it better to use an external power source for my mics before I go into the snake. I figure if the mic is powered before it hits the snake, then I'll be good.

I've seen some older AKG units and Beyerdynamic units that look big as if they had nice big power supplies. I'd like to do this if it'll be easier on me and improve my signal.

Any insight on this?

Jason

Andreas G · 15th September 2005

I know that Neumann and Schoeps build very good external phantom power supplies. But I'm not sure if an external PS will solve your problem. You still have a very fragile mic level signal to patch. Better would be a line level. At least I would build my "mic" patch with XLRs, and if you wanna split your mic signal I think a high quality splitterbox is much safer than a patchbay.

Andreas

Amplove · 15th September 2005

I'm a bit confused on this patchbay/phantom/splitter issue.

Are you saying that patchbays have problems with mic level signals?

What about when using dynamics? Is that not really a mic level signal when patching into a patchbay?

My snake is xlr but the patchbay is 1/4" TRS.

Splitter? Huh?

thx,

Jason

Andreas G · 16th September 2005

Every 1/4" TRS break acts like a little electrical condenser, that may or may not cause problems... you have to check it out.

Andreas

nosebleedaudio · 16th September 2005

I would say that internal is far superior, closer to the source, less connectors and wire. Simply put
less exposed wire the better, the Mic level is a very low level, far lower than a guitar signal for example,
so it is far more subjectable to noise ect. Big supplies are not required for phantom, very
clean and decoupled DC is. Considering most phantom mics pull about 2 to 4 milliamps(.002
amps) some as low as a 1/2 of a mill, that is not much current. Also consider this; the 48V phantom is going thru a pair of 6800 ohm resistors with a fews volts being dropped across them depending on current pulled by the mic (Ohms Law) so if you had 100 amps or 50 milliamps available to the phantom resistors that would have NO effect on that voltage drop. I would use a snake for mics to
mic input and bypass the patch bay if I could.

TedF · 16th September 2005

Mics on a patchbay is never a good idea... there's always the danger of cross patching a line output to a mic input and damaging your line output with the phantom power (not much current true, but enough votage to destroy ICs!)

External phantom power sources were designed for use where you don't have the luxury of decent phantom power on the mic input. There's no advantage unless your preamp is a real dog.

Amplove · 16th September 2005

thanks everyone. thumbsup

Jonk · 17th September 2005

Sorry to hijack,

but I thought I'd ask what you guys do with say, an Ampex 351 tube pre when you wanna use a condensor.

I mean, it's not a shabby preamp by any means, but the fact that it is a set of electronics from a tape deck means there's no phantom power.
Is an external box gonna be a real comprimise compared to having someone (or DIY'ing it) build a phantom power supply inside the preamp?

Ribbonmicguy · 17th September 2005

Here's something related to the topic from Wes Dooley:

Some background on P48 phantom mic powering requirements by Wes Dooley

A 12 volt CMC 3 schoeps or 9 volt AKG 451E (EB) mic will pull the most current from standard 48 volt powering, as those designs rely on the 6.8 K dropping resistors to bring the voltage down to match the mic's electronics. These draw almost 10 ma per mic. 48 volt power supplies, such as the Stewart units, which used non-standard lower value dropping resistors, will fry the AKG 451 series, but sound good on the Neumann TLM series.

The Neuman TLM series is the most finicky I know to power. They need lots of start up current to get their electronics into the proper operating region. I would guess the current is needed to start up the HV power supply for the polarizing voltage. If it does not get the needed start-up current, it will operate but does not sound right. The U87 uses much less current than many other condenser mics, as the electronics are a low current FET design using an output xformer, unlike the transformerless electronics of a TLM series.

The Neuman KM 80 (82,84,86) fet series actually use the phantom voltage to polarize the capsule, so for them them the P48 voltage spec of 48 volts plus or minus 4 volts has special meaning. These mics deliver a better S/N ratio at 52 volts than 48, which is the reason that Ron Streicher and I always built our phantom supplies to operate on the high side.

Wes Dooley & AEA the Ribbon Mic people

15th September 2005	#1
Amplove Gear maniac Joined: Apr 2005 Posts: 278 Thread Starter	Is External Phantom power better than In-The-Pre-Power? Is External Phantom power better than In-The-Pre-Power? So sometimes I can't patch a mic that needs phantom power through my snake (which goes straight to the patchbay) and then patch to my pre. The only way it'll work is if I bypass the patchbay and plug straight into the back of the pre (which is a pain with a big rack and all. Then I read some things (not very detailed) with people mentioning that internal phantom power degrades the sound. Is it better to use an external power source for my mics before I go into the snake. I figure if the mic is powered before it hits the snake, then I'll be good. I've seen some older AKG units and Beyerdynamic units that look big as if they had nice big power supplies. I'd like to do this if it'll be easier on me and improve my signal. Any insight on this? Jason

17th September 2005	#9
Ribbonmicguy Gear addict Joined: Apr 2004 Location: Jakarta, Indonesia Posts: 412	Here's something related to the topic from Wes Dooley: Some background on P48 phantom mic powering requirements by Wes Dooley A 12 volt CMC 3 schoeps or 9 volt AKG 451E (EB) mic will pull the most current from standard 48 volt powering, as those designs rely on the 6.8 K dropping resistors to bring the voltage down to match the mic's electronics. These draw almost 10 ma per mic. 48 volt power supplies, such as the Stewart units, which used non-standard lower value dropping resistors, will fry the AKG 451 series, but sound good on the Neumann TLM series. The Neuman TLM series is the most finicky I know to power. They need lots of start up current to get their electronics into the proper operating region. I would guess the current is needed to start up the HV power supply for the polarizing voltage. If it does not get the needed start-up current, it will operate but does not sound right. The U87 uses much less current than many other condenser mics, as the electronics are a low current FET design using an output xformer, unlike the transformerless electronics of a TLM series. The Neuman KM 80 (82,84,86) fet series actually use the phantom voltage to polarize the capsule, so for them them the P48 voltage spec of 48 volts plus or minus 4 volts has special meaning. These mics deliver a better S/N ratio at 52 volts than 48, which is the reason that Ron Streicher and I always built our phantom supplies to operate on the high side. Wes Dooley & AEA the Ribbon Mic people __________________ ------------------------------ Harmoko Aguswan Big Knob Studio Right Track Productions ------------------------------ On one hand, I can certainly sympathize with the approach of "Hey, I can't hear any difference, so why should I pay that much?". On the other, I wonder why anyone who can't hear a difference is recording, mixing, or producing records. -DAVE MARTIN thumbsup

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15th September 2005	#2
Andreas G Lives for gear Joined: Mar 2005 Location: Germany Posts: 1,097	I know that Neumann and Schoeps build very good external phantom power supplies. But I'm not sure if an external PS will solve your problem. You still have a very fragile mic level signal to patch. Better would be a line level. At least I would build my "mic" patch with XLRs, and if you wanna split your mic signal I think a high quality splitterbox is much safer than a patchbay. Andreas

16th September 2005	#4
Andreas G Lives for gear Joined: Mar 2005 Location: Germany Posts: 1,097	Every 1/4" TRS break acts like a little electrical condenser, that may or may not cause problems... you have to check it out. Andreas

16th September 2005	#5
nosebleedaudio Lives for gear Joined: Jun 2005 Location: Birmingham, AL USA Posts: 3,703	I would say that internal is far superior, closer to the source, less connectors and wire. Simply put less exposed wire the better, the Mic level is a very low level, far lower than a guitar signal for example, so it is far more subjectable to noise ect. Big supplies are not required for phantom, very clean and decoupled DC is. Considering most phantom mics pull about 2 to 4 milliamps(.002 amps) some as low as a 1/2 of a mill, that is not much current. Also consider this; the 48V phantom is going thru a pair of 6800 ohm resistors with a fews volts being dropped across them depending on current pulled by the mic (Ohms Law) so if you had 100 amps or 50 milliamps available to the phantom resistors that would have NO effect on that voltage drop. I would use a snake for mics to mic input and bypass the patch bay if I could.

16th September 2005	#6
TedF Gear nut Joined: Aug 2005 Location: UK Posts: 77	Mics on a patchbay is never a good idea... there's always the danger of cross patching a line output to a mic input and damaging your line output with the phantom power (not much current true, but enough votage to destroy ICs!) External phantom power sources were designed for use where you don't have the luxury of decent phantom power on the mic input. There's no advantage unless your preamp is a real dog.

17th September 2005	#8
Jonk Lives for gear Joined: Jan 2005 Location: Portland, OR Posts: 563	Sorry to hijack, but I thought I'd ask what you guys do with say, an Ampex 351 tube pre when you wanna use a condensor. I mean, it's not a shabby preamp by any means, but the fact that it is a set of electronics from a tape deck means there's no phantom power. Is an external box gonna be a real comprimise compared to having someone (or DIY'ing it) build a phantom power supply inside the preamp?