Choosing tubes for a tube mic

mpedrummer · Post by **mpedrummer** » Fri Feb 20, 2009 6:06 am

I'm gearing up to mod an Apex 460. There's a ton of information out there on the intarwebs about modding this mic - what capsules, what transformers, even what electrolytics...

There is also a lot of discussion of tube models, but nothing I can find stating a preference for one brand over another.

I've settled on wanting a 6072a, because of the additional headroom it affords in the design. But which one? For one thing, I'm having a hard time finding them...Electro-Harmonix makes them, but that was the only one I could find on tubedepot (that's currently in stock)

pcX has the EH, the EH Gold pin, and a NOS Amperex. What's the difference?

Sorry for my noob questions...I'm just starting to foray into the world of tubes, and a lot of it seems to be "ooo, there's a tube, it's better!"

Thanks
Tim

mrc · Post by **mrc** » Fri Feb 20, 2009 7:22 am

Got my 6072a, T-14 and C-12 capsule from Peluso for the 1150, he has the 67 and 47 capsules, and the N style transformer as well.
mrc

dfieldmusic · Post by **dfieldmusic** » Fri Feb 20, 2009 8:33 am

www.watfordvalves.com has quite a lot of info regarding different brands of different valves - some seem to be designed to break up at lower volumes with high-mid peaks whereas others are cleaner and flatter. I tried an ElectroHarmonix 12ax7, which sounds great in our Deluxe Reverb amp, in a TLaudio valve pre and it sounded pretty odd - in fact, it sounded pretty bad - worse than the cheap stock Sovtek - but I put a phillips valve and that cleaned things up a lot - sounds significantly better. Likewise, just put a Harma valve in a Rode K2 and that's also improved things quite a bit - turned into my new fave mic on bass cabs and bass drums.

Dakota · Post by **Dakota** » Fri Feb 20, 2009 4:01 pm

mpedrummer wrote:pcX has the EH, the EH Gold pin, and a NOS Amperex. What's the difference?

Basically, there are modern tubes, all or almost all of which are made in china or russia. Pros: cheap and plentiful. Cons: comparatevely brittle and unsubtle sounding.

Or NOS or recovered vintage tubes. The best of which were made to a much higher standard of tone and function than any made now. Telefunken, Mullard, Amperex, RCA, etc. Pros: if well chosen, you get "magic" timbre. Cons: probably a level or two more expensive, and requires some research ahead of time before purchasing.

Example: I have a Rode NTK (originally w/ stock modern tube) that displays all the usual things people do and don't like about the mic. Unpredictably excellent on some sources, unpredictable and irritating fizz/fuzz in the upper mids and highs on some sources. Never could trust that mic. Put in a NOS Amperex Bugle Boy from the 60s/70s, and wow. World of difference. Fizz gone, remarkably sweet tone, more detail, 3 dimensional sounding. Saved the mic.

Useful information here: http://www.audiotubes.com/. Just click into the 12ax7 box in the upper left or whatever, and learn how to geek out like a wine connoisseur.

mpedrummer · Post by **mpedrummer** » Sat Feb 21, 2009 5:16 am

Oh crap, there goes my weekend

Thank you so much! That website is awesome, as was your explanation.

Tim

dave watkins · Post by **dave watkins** » Sat Feb 21, 2009 6:30 am

other than the internet, you can find a lot of NOS or just used tubes at ham radio shows/swap meets. the condition is always going to be questionable, but when when you are only spending a couple bones per tube instead of say $20+, it can be worth it. and you can usually find tube testers and other fun stuff while you are at it.

mpedrummer · Post by **mpedrummer** » Sat Feb 21, 2009 6:49 am

So, are 6072a just extremely rare? I'm having a hell of a time finding them...the place I ordered from just emailed offering to substitute a 12AY7 instead...similar, but not the same.

The audiotubes.com site doesn't have information on them, and show zero in stock...bleh.

Suggestions?

Thanks
Tim

Dakota · Post by **Dakota** » Sat Feb 21, 2009 1:26 pm

mpedrummer wrote:So, are 6072a just extremely rare? I'm having a hell of a time finding them...the place I ordered from just emailed offering to substitute a 12AY7 instead...similar, but not the same.

The audiotubes.com site doesn't have information on them, and show zero in stock...bleh.

Suggestions?

Thanks
Tim

Yes, 6072a's are rare-ish, but not unobtainable.

Did you check ebay? Searching "6072a" in Electronics, at the moment I see about ten results come up, a few of which are vintage. Amperex, GE, RCA.

http://shop.ebay.com/items/_W0QQ_sopZ10?_nkw=6072a

Like anything else on ebay, prices vary from bargain to ridiculous. If you take your time, you can get great old tubes cheap.

And agreed +1 for radio meets, electronics flea markets. That's a long term strategy, though.

Also, write emails to sites like audiotubes.com and others. Even if what you want isn't listed, they may have a line on how to get what you're looking for.

rodabod · Post by **rodabod** » Sat Feb 21, 2009 1:46 pm

For 6072s, I'd aim for GE - either noise-selected or 5-star. Otherwise try a 12AT7 / ECC81. These two tubes have lower output impedance than the 12AX7 which isn't a great choice in this mic. I'd tend to always go for NOS, but don't get ripped off.

mpedrummer · Post by **mpedrummer** » Sat Feb 21, 2009 2:09 pm

Yeah, we'll see how this goes...there's a definite combination of impatience and curiosity going on here...I want to do this right, and understand what/why I'm doing things, but also want to have the mic operational before a session in mid March!

I wound up getting a NOS 12AY7 - I had ordered a 6072a, but they were out of stock. I know that the 12AY7 is more or less equivalent, but it's half the cost, so...something's different, right? Is this one of the "commercial vs military" grade differences, or is something else at play?

I've also had trouble finding information about the 6072a...even the audiotubes website didn't have any information.

And ebay....damn ebay. I kept getting sniped at the last minute on ebay

Thanks guys!
Tim

Dakota · Post by **Dakota** » Sat Feb 21, 2009 3:57 pm

You're welcome. Best of luck.

Get bidnapper.

@?,*???&? · Post by **@?,*???&?** » Sat Feb 21, 2009 4:24 pm

If you tried searching on this site, the search functions suck.

6072a is a very common tube. Lots of manufacturers to choose from. My favorites are Telefunken (most transparent), RCA (very rock and roll) and Tung Sol (just sounds like audio to me).

Ebay them. Get many. As these are pinned the same and are swappable with other tubes, you can get away with a 12AX7 (more gain) in the same mount, but also try a 12AT7 (less gain).

I got a bag of 12AT7s for pennies.

Definitely experiment here. Also, if you've got the mic open, try swapping your electrolytics with Nichicon parts. You'll notice a significant difference in transient response.

stitch · Post by **stitch** » Sat Feb 21, 2009 7:09 pm

I posted an on going list of 12A*7 preamp tubes and their variants.
I've had fun going through this list: TUBES

This might be interesting to some...

Cheers!

mpedrummer · Post by **mpedrummer** » Sun Feb 22, 2009 7:56 am

Cool, thanks. I actually already sourced some Black Gate caps for the project. I'll have to look into the Nichicon - I know the BG are on the way out since they stopped making them.

I will confess to having not searched TapeOp specifically - I've been googling with no luck, and already had a conversation going with my imaginary internet friends here, so I figured I'd just ask!

Tim

Bill @ Irie Lab · Post by **Bill @ Irie Lab** » Wed Feb 25, 2009 3:02 pm

My musical collaborators have been calling a 'know it all'

Maybe has some thing to my being a school teacher - apologies to anyone and everyone.

I'm here to learn too.

that said- everyone who has tube stuff, get a tube tester.

and a finger nail to check for microphonics.

thank you for listening.

Bill

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Choosing tubes for a tube mic

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