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Stephen Boyke
 
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Default 12AX7 and 12AU7 for tube microphone

I've purchased a microphone for recording (CAD VX2). It uses a 12AX7
for the head amplifier and a 12AU7 to run the line driver. I'm interested
in getting different brand tubes for it (the current X is a Sovtek and the
current U is a Phillips). The Phillips makes lotsa noise and is defective.

Anyway. Does anyone have any suggestions? I'm looking for very very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.

I've looked at some of the vintage tube dealers online. I'm confused.

Thanks for any input!
--
Stephen Boyke


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Gregg
 
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From experience, I can highly recommend the Russian 6N2P as a replacement
for the 12AX7 and a 6N1P for the 12AU7.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca
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Phil Allison
 
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"Stephen Boyke"


Anyway. Does anyone have any suggestions? I'm looking for very very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.



** Get real and use a mic with a FET pre-amp.

The hissing noise and microphony are what gives a tube mic its sound.






.......... Phil


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Robert Casey
 
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Stephen Boyke wrote:

I've purchased a microphone for recording (CAD VX2). It uses a 12AX7
for the head amplifier and a 12AU7 to run the line driver. I'm interested
in getting different brand tubes for it (the current X is a Sovtek and the
current U is a Phillips). The Phillips makes lotsa noise and is defective.

Anyway. Does anyone have any suggestions? I'm looking for very very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.



As Phil noted, tubes can be noisy, but from your discription, you need a
new 12AU7.
But how do you know that? Does the noise remain if you remove the
12AX7? Are the
tubes inside the microphone itself (I'm not familiar with the CAD VX2)?
Maybe the
mic element itself is making some of the noise?

As for what brand of tubes to get as replacements, That's more a matter of
opinion than anything else. NOS tubes made during the tube era might be
good bets. Mil spec tubes might have better microphoonics and noise, but
in the late 70s lots of bad tubes were made for the military.... Many
were ordered,
delivered and never used.

  #5   Report Post  
Phil Allison
 
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"Robert Casey"


As Phil noted, tubes can be noisy, but from your discription, you need a
new 12AU7.
But how do you know that? Does the noise remain if you remove the
12AX7? Are the
tubes inside the microphone itself (I'm not familiar with the CAD VX2)?



** See: http://www.cadmics.com/vx2.htm


The noise spec ( 13 dBA equivalent SPL ) is very good - I suspect
the mic capsule runs at a pretty high DC bias voltage to get that result
with a tube head amp.





............ Phil




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Stephen Boyke
 
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Robert,

Yeah, the original 12AU7 was making a lot of noise through the output
trannys. I replaced it with a cheap new one. About 90% of he noise
disappeared, and the noise that remains has a slightly different character.
I just want to find a very very quiet replacement.

Thanks!
--
Stephen Boyke

in article , Robert Casey at
wrote on 4/16/04 9:39 PM:

Stephen Boyke wrote:

I've purchased a microphone for recording (CAD VX2). It uses a 12AX7
for the head amplifier and a 12AU7 to run the line driver. I'm interested
in getting different brand tubes for it (the current X is a Sovtek and the
current U is a Phillips). The Phillips makes lotsa noise and is defective.

Anyway. Does anyone have any suggestions? I'm looking for very very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.



As Phil noted, tubes can be noisy, but from your discription, you need a
new 12AU7.
But how do you know that? Does the noise remain if you remove the
12AX7? Are the
tubes inside the microphone itself (I'm not familiar with the CAD VX2)?
Maybe the
mic element itself is making some of the noise?

As for what brand of tubes to get as replacements, That's more a matter of
opinion than anything else. NOS tubes made during the tube era might be
good bets. Mil spec tubes might have better microphoonics and noise, but
in the late 70s lots of bad tubes were made for the military.... Many
were ordered,
delivered and never used.





  #8   Report Post  
Tom Schlangen
 
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Hi Stephen,

I just want to find a very very quiet replacement.


Try some NOS JAN Sylvania 6198W, which should neither
be too hard to find, nor be overly expensive. I recently
got a pair via (german) Ebay for less than 10 Euros
w/o shipping. These are the quietest and least microphonic
12AU7 family members I have in my drawer - way better/quieter
than for example current production JJ/Tesla and Svetlana
ones. And even cheaper than current production samples ...

I have some NOS JRC RCA 5814A, too, which are also very
quiet, but one out of four is way more microphonic than
the other three ones. The JAN Sylvania 6198W samples are
still quieter.

If you don't mind costs, hunt for legendary TFK ECC802S,
but I can't tell from personal experience how good these
actually are. At least the specs as layed down for the
whole TFK ECC80x family were extremely rigid.

Serpentine

--
A gleekzorp without a tornpee is like
a quap without a fertsneet (sort of).
  #9   Report Post  
Stephen Boyke
 
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Default

in article , Stephen Boyke at
wrote on 4/17/04 8:07 AM:

Robert,

Yeah, the original 12AU7 was making a lot of noise through the output
trannys. I replaced it with a cheap new one. About 90% of he noise
disappeared, and the noise that remains has a slightly different character.
I just want to find a very very quiet replacement.

Thanks!
--
Stephen Boyke

in article
, Robert Casey at
wrote on 4/16/04 9:39 PM:

Stephen Boyke wrote:

I've purchased a microphone for recording (CAD VX2). It uses a 12AX7
for the head amplifier and a 12AU7 to run the line driver. I'm interested
in getting different brand tubes for it (the current X is a Sovtek and the
current U is a Phillips). The Phillips makes lotsa noise and is defective.

Anyway. Does anyone have any suggestions? I'm looking for very very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.



As Phil noted, tubes can be noisy, but from your discription, you need a
new 12AU7.
But how do you know that? Does the noise remain if you remove the
12AX7? Are the
tubes inside the microphone itself (I'm not familiar with the CAD VX2)?
Maybe the
mic element itself is making some of the noise?

As for what brand of tubes to get as replacements, That's more a matter of
opinion than anything else. NOS tubes made during the tube era might be
good bets. Mil spec tubes might have better microphoonics and noise, but
in the late 70s lots of bad tubes were made for the military.... Many
were ordered,
delivered and never used.






--
Stephen T. Boyke


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Phil Allison
 
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"Stephen Boyke" wrote in message
...
Thanks Phil. I have several FET mics too.



** Then why did you buy a tube mic if you dont like the effect that using
tubes gives ??

Oh, hang on a mo, I see you are a top poster - explains
everything.


............ Phil


--
Stephen Boyke

in article , Phil Allison at
wrote on 4/16/04 9:18 PM:


"Stephen Boyke"


Anyway. Does anyone have any suggestions? I'm looking for very

very
low noise, low microphonics, etc. To the extent they can add as little
color to the sound of the circuit as possible, the better.



** Get real and use a mic with a FET pre-amp.

The hissing noise and microphony are what gives a tube mic its

sound.






......... Phil








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