Ultra High Gain Mic Preamp

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Siegfried Meier

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Joined
Jul 2, 2004
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Location
Ontario, Canada
Hey guys,

Doing a lot of acoustic stuff lately, and none of my pres (custom built or commercial offerings) are really enough for quiet, dynamic acoustic recording.

What can any of you suggest - either a DIY build, or a commercial product - that will be the absolute highest output with minimal self noise?

Great River?  Millennia?
 
the more gain you add your adding noise as well.  might look at what the orchestral guys are using and try those out.


Siegfried Meier said:
I'm thinking the Millennia HV3C might be the best option.

Anyone?

http://www.mil-media.com/hv-3c.html#ph

We got some at work. You will find those a lot on the scoring stages. They are quiet and sound good.
 
You can add gain to a signal with a later gain stage without seriously degrading the S/N further. The S/N will be dominated by the first stage so if it is good quality and running full up. You won't see any significant benefit from putting more gain in that first stage.

JR

 
v76 has best s/n at high gain over here, but super long project, money and labor very high, 400 bucks for the input xfmr, but it kills everything else,

but there is the DIY western electric 417a, amazing preamp, one stage, ultra detailed high end, super microphonic, you touch the chassis and you hear ziiiiiiiiiiiiiiiiiiiiing
in the phones for about 10 seconds, quiet,cheap and  easy to build, uses a dukane input and maybe cap output, have to open it up, might be a thread on it,

my solid state choice would be the quad 8 strapped for max gain, also very nice upper freqs,

now if you have condenser mic, which you should have for acoustic stuff, then other options open up,

Langevin AM16, V72,

WE- 3 resistors, 1 cap, 1 input xfmr,

rubber grommets help the microphonics,









 

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What mikes?

If dynamic (including ribbons), there's stuff that gets within 2dB of the theoretical noise from the resistance of the mike.  Have a look at http://tech.groups.yahoo.com/group/micbuilders/files/Ricardo/ActiveRibbon/ RibbonDMP3.doc  You have to join.  Less than 1dB from the excellent Millenia Media HV3

If condensor, the Earthworks are the quietest mike preamps in the known universe.  None of the DIY stuff is in the same league.
 
Siegfried Meier said:
Wayyyyy too noisy.  That's why I'm using now.  Not good enough...

I need high gain, NO noise, whatsoEVER!

This is contrary to the laws of physics. The noise in a 150 ohm resistor is about -132dBu at room temperature. If you have a noise free preamp with 70dB of gain the output noise will be -132 + 70 = -62dBu. The only way to improve this is to reduce the temperature.

Cheers

Ian
 
gemini86 said:
Eureka! Refrigerated preamp rack! I'm off to the hardware store, be back in a week or so.

I looked at that decades ago and the temperature is relative to absolute zero (minus a few hundred C)... so think cryogenically cooling a microphone, and not have it behave a little screwy. Then don't breath on it. "We need a recording break to de-ice the mics".  ;D 

Don't expect much from adding a fan to your rack if the noise is dominated by the mic source impedance (or electronics).  8)

JR

 
Refrigerated preamp rack!

No, refrigerated mic/recording room!

The secret for quiet recordings is in the microphone and the room, not the preamp. Get a decent modern large-diagrphragm, transformerless condenser mic (just a random choice from my own list: Microtech-Gefell M930). These types have the lowest currently possible noise figure (around 7 dB-A) such that the background noise of most recording spaces will dominate and so high sensitivity that the preamp will not matter anymore.

If you insist on a different particular mic type (dynamic, ribbon, old condenser) for sonic reasons, you'll have to accept a compromise.

Samuel
 
And what preamps do you guys end up using ?  [ samual ? ]

I use the Millennia [ or the studer pres in the board ]  with B&K / DPA's with a broadcaster I work for and
my Great River MP-2's [ designed to be quiet enough for ribbons ] w/ schoeps for my freelance Orch gigs  .
I think these days there's decent selection without going for thee most expensive , need not be a millennia .
 
Samuel Groner said:
Refrigerated preamp rack!

No, refrigerated mic/recording room!

The secret for quiet recordings is in the microphone and the room, not the preamp. Get a decent modern large-diagrphragm, transformerless condenser mic (just a random choice from my own list: Microtech-Gefell M930). These types have the lowest currently possible noise figure (around 7 dB-A) such that the background noise of most recording spaces will dominate and so high sensitivity that the preamp will not matter anymore.

If you insist on a different particular mic type (dynamic, ribbon, old condenser) for sonic reasons, you'll have to accept a compromise.

Samuel

Precisely. The key to the achieved signal to noise ratio is nearly always not the preamp but the sensitivity of the microphone. With modern low self noise condenser mics, the noise limit is determined by the acoustic environment and not the preamp or mic.

My home made tube mic pres have an EIN of no better than -125dBu but with 75dB of gain and a Rode NT1-A connected the noise acoustic noise floor is well above the electronic one.

Connect my Grampian GR2 ribbon to the same preamp, crank up the gain to 75dB and you can clearly hear the hiss of the electronics.

Cheers

Ian
 
I've had the same problem when recording singing bowls.
I ended up using dpa 4003s into DBX 786 preamps, I could hear planes passing, still not quiet enough.
I think the best option today is the new Neumann Digital mics, you can record flies with those...
 
In my experience the SSL 9k is one of the quietest & clearest mic amps I have, it also has bucket loads of gain.  This might be what you're after for acoustic recordings  ...........

However, that is one of the reason I personally hardly ever use my pair.  I like the Neve, API, langevin etc mojo
 
Rob Flinn said:
In my experience the SSL 9k is one of the quietest & clearest mic amps I have, it also has bucket loads of gain.  This might be what you're after for acoustic recordings  ...........

However, that is one of the reason I personally hardly ever use my pair.  I like the Neve, API, langevin etc mojo

same here. 9K all the way for quiet stuff!
or a pair of Altec 9470...

Mattia.
 
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