Build a low-noise, high-quality tube microphone

[commanderberti]

What are your experiences with what the last dB of noise improvement brings? PSU filters, special capacitors, transformers, which tubes... I'm grateful for all your tips!! Thanks

 

[RuudNL]

A good tube! (The quality of tubes nowadays isn't what it used to be...)

 

[commanderberti]

A good tube! (The quality of tubes nowadays isn't what it used to be...)

thanks, what tubes ecc83 can you recommend

 

[LevinGuitar]

A good capsule too, some of the cheap ones can be slightly noisy.
I remember I was amazed of the silence more than of the sound when I tried for the first time a real K49 in mint condition.

 

[gyraf]

..basically, the ECC83 is not suitable as capacitor microphone front end, grid leak and miller capacitance are prohibitive..

The reason the chinese started using it for mics was most probably just that they could get very-cheap "only-one-half-working" ecc83's, rejects from current production (check the original tube in there - most of the time the "other half" of the mounted dual triode is defective).

/Jakob E.

 

[commanderberti]

..basically, the ECC83 is not suitable as capacitor microphone front end, grid leak and miller capacitance are prohibitive..

The reason the chinese started using it for mics was most probably just that they could get very-cheap "only-one-half-working" ecc83's, rejects from current production (check the original tube in there - most of the time the "other half" of the mounted dual triode is defective).

/Jakob E.

which tube(circurit) do you prefer?

 

[kingkorg]

What are your experiences with what the last dB of noise improvement brings? PSU filters, special capacitors, transformers, which tubes... I'm grateful for all your tips!! Thanks

How quiet do you really need a tube to be? I personally use tube mics for their coloration which starts to show at high-ish SPL. If you use a tube mic at low SPL where noise is starting to play a role you don't really get much of the tube goodness. My approach is FET for low noise, Tube for louder stuff where these mics really shine. Unless you record something with crazy dynamic range. I feel when people talk about tube mics noise as an issue it's where it becomes really obvious, where you clearly hear the noise in the recording. Couple of db in noise floor difference shouldn't be a deal breaker.

I am also a synth guy, and we use noise as an enhancement. What is a Juno 6 without it's noisy chorus? There's something nice about little bit of noise, but that's just me.

 

[rogs]

I am also a synth guy, and we use noise as an enhancement. What is a Juno 6 without it's noisy chorus? There's something nice about little bit of noise, but that's just me.

A good example of a nice bit of extra noise is the key click and generator 'leakage' on a Hammond organ....
Laurens Hammond himself spent years trying to minimise those things -- only for modern 'clones' of the original tonewheel organs to actually add these noises back in as a feature ......
You can 'dial it out' these days if you want, but it's not the same without the extra 'noise'....

The newest Yamaha clone even allows you to deliberately introduce hiss into the simulated Leslie amplifier..... just like the original
(it's a fully adjustable hiss level now of course! )

 

[RuudNL]

IMHO the ECC83 (12AX7) is the worst tube to use in a condenser microphone.
Personally I have good experiences with the EH EF86 and the Russian 6SB6-V.
(I even replaced the original tube in my Neumann U67 reissue with an EH EF86, resulting in a lower noise floor)

 

[Marik]

Here is a more or less complete list of the tubes in more or less common tube mics.

http://audiotubes.com/mictubes.htm
The only omissions I can think of are C3G (Pegasus mic), 6S31B, and 5842/417A. Some tubes might look unusable--for example aforementioned 12AX7. Frame grid tubes (like 6922, or 6N1P) might look questionable, but then it is rather about implementaion. In general, it is better to look for the tubes with lower mu, lower Rp and higher transconductance. This allows you to use lower ratio transformers--it is easier to make them well in comparison to high (10:1--12:1) ratios.

If your goal is low noise then you better use jFets. Another way is making a first stage on jFet followed by a tube. This way you will take a good care of tube grid leak problems, as well. You could also use jFet as a lower shoulder of a cascode and then a frame grid tube on top--this arrangement will make perfect sense.

Hope it helps.

Best, M

 

[ElSmurf]

Totally unrelated but whenever noise is discussed I remember Dave Pensado's view on noise in the mixing environment : "it sounds like the ocean."

 

[LevinGuitar]

I would add EC70 made by Mullard and EF762 by RWN/RFT to the best audio tubes. For now that were the nicest tubes I found when using with grounded cathode. Still not same as AC701, but quite closer than the rest of the famous subminis.