Tube swapping with my Condensor Mic

[CharlieG]

Hey All, I have an ADK TC, it's a tube condensor mic. It has what appears to be a 12ax7 but the specs say it is a 6072A valve, I don't know the difference. I have an old Mcintosh 240 with some old telefunken 12ax7's and I was thinking about putting one in the microphone. I'm pretty new to tubes and don't know if theres a reason this might not work or might hurt anything. Can somebody help tell what's going on, if this should work or not?

Here are the TC Specs, ADK Microphones - Audiophile Series Microphone Catalog - Model TC


-Charlie

 

[SY]

12AX7 and 6072A are quite different (same pinout so not "it's gonna explode" different). The closest thing I know to a 6072A is a 12AY7.

 

[CharlieG]

So does that mean that a 12ax7 will not work with the mic? what are other tube options that might work for me?

 

[SY]

It will work, just not terribly well. 12AY7 is still your best sub. They're not cheap ($50-100), but if you have patience, you can probably score a few for a reasonable sum.

12AT7/ECC81 is a bit farther away, but a lot closer than a 12AX7/ECC83.

edit: Saw some Russian 6072A on EBay for $15.

 

[rmb]

Agree with SY and others. 12AX7 is a high mu dual triode. Most of the ones I get are noisy or microphonic in preamps like the Altec 1567a. The 12AX7 was not designed to operate at the high grid impedance with a condenser mic. The 12AT7 is also a high mu triode, designed for use at VHF frequencies in some FM tuners. The 12AT7 is perhaps more "stable" than a 12AX7 but not a good choice for a condenser mic. The 12AY7/6072 is a medium mu triode. It was designed primarily for industrial use. The 12AY7/6072 is a good mic tube, proven with the AKG C12 and other condenser mics.

 

[6A3sUMMER]

The 12AY7 is a current production tube (at least 1 source).

There is just a little more filament current specified for the 6072/6072A (0.175A @ 12V, 0.35A @ 6.3V; versus 0.15A @ 12V, and -0.3A @ 6.3V for the 12AY7).
Otherwise they are the same.

I have a pair of current production 12AY7s, and they work great (and they perform just like the tube manual specifications say they should).
And, I got the brand new production ones for not too much $.
Go for it.