This  came out of my AKG Solid Tube Mic. Seems 12AX7 is the "known" replacement in the intertubbies. Anyone have any suggestions for a source for a "quality" replacement ? I think this one is on it's last leg as it's 15+ years old.





Should I just go to local music store and get Groove Tubes 12AX7 Gold series? Or is there a ultra cool ultra hip ultra stoke Mooch out tube I should buy?

Yes!!

Mesh


Yes!!

Bapu: Mesh, should I get Vanilla or Chocolate?
Mesh: Yes!!

I would have thought it would have been a 6072 in the AKG mic.


If it's really a 12AX7 then you can probably try any of them.

Do you have a schematic? If the circuit is Cathode biased then you can just plug and play.

That circuit may actually require a bias measure and fine tune adjustment for each tube, so you should try to find out.

With microphones and the hi gain associated you will appreciate a tube that is very low in noise... so usually a mic tech will try several tubes looking for the lowest noise. It has to be quieter than something that might work good in a guitar amp. So, it is the difference between good and very good.

You will also see that various tubes have very slight to dramatic different response in both frequency and dynamics.

It's hard to think that a brand name recommendation will serve you better than trying what you can find easily.

A new Russian Mullard?

A old RCA 7025? 

Early 1980's JAN Phillips ECG?


Why do you think your old tube is bad?

Some of my favorites that I play in my guitar are 60 years old and going strong.



In any event, you probably live in an area that has a highest tube mic tech per capita ratio so you are gonna be ok.

:-)

Good Luck.


best regards,
mike

there was a tube dude called Bowie over on GS who was pretty straight and a good source for replacements, look him up.

bapu

Mesh


Yes!!

Bapu: Mesh, should I get Vanilla or Chocolate?
Mesh: Yes!!

I forgot to add....just giving it a friendly  
 
Chocolate for me please....Yes!!

Yep it's a 12AX7:

http://www.akg.com/mediendatenbank2/psfile/datei/37/solidtube4055d251a2cd0.pdf

McQ, as I examine the circuit board the tube mounts on I see no evidence of a any adjustment pots of any kind.

I "think" the tube is going in that the mic seems to record a mild by concerning distortion in the same signal chain that I use for my  AEA R-84 (sans Ribbon switch engaged on Grace M-101 preamp). 

Now that I have the tube out, I guess I should have it checked before plopping down $20, $30, $60 or $160 on some panacea of tube glory, no?

Yep, what was mentioned above.

Yes, I just read the owners manual.

Plug and Play.


Have fun with it.

You can search out special model, vintage, pedigree tubes etc. or just try some.


The 12Ax7 was not used in vintage microphones because it is, generally speaking, noisy compared to those that were more commonly used.

It's fine in systems that use less gain and don't need super low noise floors, and so you see it used in guitar amps and radios and some hi-fi.

The 7025 was the label used for 12Ax7s that were culled out because they were low noise.

There are several brand of NOS 7025s. RCA, Amperex etc. that you might try.

Some of the relatively new, made in USA JAN Phillips ECG stock from the early 1980's were pretty low noise.

The various Sovtek brands can be nice, but the consistency seems varied... you have batches of good and batches of YMMV.


Try a few cheap new Russian or Tesla tubes and maybe an old 7025 and one of the 80's JANs.

I'll bet you'll hear differences and I wouldn't be surprised if you find one that sounds smooth but ends up having more noise than another that may not sound as smooth.

Stuff like that.



best regards,
mike