12au7 variants ?

HI I have another question? I have been reading up on variants of the 12au7 tube and some said to make sure and check with the designer of the amplifier that it can safley run them as some have different "filament voltage needs"? so here goes...6189/5814/cv491/6680/7730/e80cc/6085/b749.Thanx so much I really appreciate your patience with what to you guys probably think are silly questions but I don't have your electrical knowledge . Scott

a fairly quick way, I would think, to get those details is to search the net for data sheets on those tubes, you'd be surprised how much info is out there for tubes.
Then you can download those tech files and you'll have permanent copies on your system for future references.
Here is an example of what I found for the 5814 by just entering the tube number followed by 'data', http://pdf1.alldatasheet.com/datasheet-pdf/view/230184/ETC2/5814.html

In North American tube nomenclature, the number "up front", i.e. the 12 in 12AU7/AX7/BH7 etc. or the 6 in 6CG7 or 6146A denotes the heater voltage. The 12 means 12 volts; the 6 means 6.3 optimally. Some European tubes (i.e. the 6922) also follow this convention, but how you'd derive the heater volts for a KT-88 without looking it up (it's 6 volts as well) is beyond me, except that its specs are comparable to an American 6550, which is also 6 volts as designated by the 6 up front.
Pre-amp tubes are a bit flexible, in that there are some 7-volt-heater variants of the 6922 which work fine in a 6-volt hole. That's not the case for power tubes, though. If the filament voltage is wrong everything goes pear-shaped.
Somebody with brains, correct me if I'm wrong here.

OK so what are the parameters of my VTA ST_&) WITH THE low gain board[Bob said that 12BH7's and 12AU7's are ok ...what do I look for ,I am sorry I am so ignorant I just don't even know where to start.But I want both Montanna Way and deepee99 I very much appreciate your INVALUABLE help.Thank you so much. By the way I got my KT 120's up and running,and I think I may just stay with the clear top 12au7's they completely blow away ALL others in my set up[LAsCala, VTA ST-120,DENON cd player... NO PRE AMP!!! took the Mac pre out of service .only use it with the vinyl. and my goodness ,oh yeah and wow too.Scott

scottlowe wrote:OK so what are the parameters of my VTA ST_&) WITH THE low gain board[Bob said that 12BH7's and 12AU7's are ok ...what do I look for ,I am sorry I am so ignorant I just don't even know where to start.But I want both Montanna Way and deepee99 I very much appreciate your INVALUABLE help.Thank you so much. By the way I got my KT 120's up and running,and I think I may just stay with  the clear top 12au7's they completely blow away ALL others in my set up[LAsCala, VTA ST-120,DENON cd player... NO PRE AMP!!! took the Mac pre out of service .only use it with the vinyl. and my goodness ,oh yeah and wow too.Scott

I assume you meant VTA ST-70 (caps lock key on?).
Can't help from actual experience, but in my M-125s and Roy's pre-amps I don't think you can top the clear-tops.
Every tube-maker back than had a "house sound" be it Amperex, Phillips, or RCA. I just think, having rolled a lot of tubes, that RCA got it right.

Yes when i get new old stock......ones i wont are RCAs an GE then i look at others.....12AU,12AT,12BH,6AN8,6SN7....RCAs always sound like there Tone right on for me......but with diff caps in the setup the GEs can be vary sweet Cj preamps are GEs.........to get the sound you wont you got try them all to know..... thay all have there sound...have fun with tube.....
SS guys better like there sound...cant just chang drivers....hehe.....
i say this as of to day i am runing a Krell amp an hhscott 355 tube pretuner.....an lov it......man Audio...is a trip.........


Thanks for the site Bob.........

Hi Scott ---

If you go to this tube search-engine:
http://www.duncanamps.com/tdsl/tubesearch.php

and type-in each 12au7 "equivalent tube" that you mentioned in your original question, you will see the electrical characteristics of that variant tube.  Sometimes there will be a link to a graph of the tube characteristics and sometimes not.

Assuming that the variant matches the 12AU7 electrically, there is no guarantee that it will sound the same as the 12AU7.  We each hear differently and what sounds great to someone may sound terrible to you based upon your listening space and your electronics.

Tube Rolling is strictly a "trial and like or dislike process".  Some folk here like the 12AU7(A) and some like the 12BH7, some like RCA Clear-tops and some don't.

A variant of the 12AU7 that I like is the Radio Technique (RT) 12AU7WA which was a tube made for the French Military in the 1950's and is exceptionally smooth and natural sounding.  I have one of Bob's ST-120s and I use two of the RT 12AU7WA's in the outer positions of the VTA Board.  The center is currently occupied by a Heath/Mullard 12AU7 and I like the composite sound very much.

What are you currently using in the three tube positions of your VTA board?  

Let us know.

Stew

I have a VTA ST-120 (465 hrs) with RCA 12BH7 in the out board positions and a sweet sounding Panasonic 12BH7 in the center, KT-120 drivers (300 hrs) biased up at .580V through a MAC mini using a Schiit Gungnir DAC (400 hrs) to Kilpsch Heresy speakers sounds sweet to me.
I have tried the following 12AU7s & 12BH7 Amprex, Bugle boy, Orange label, Telefunken, RCA Clear tops, Philco, Articus, Tung-sol, Reytheon, Philco, CBS, Siemens ECC 81, Sylvania JAN 587.
I originally started out with Sovtek KT-88 output tubes before switching to the Tung-Sol KT-120s as for rectification I'm currently using a JJ GZ34 and have on hand but havent tried a Weber copper cap WZ 68, Sovtek 5U4G and Sovtek 5AR4
Addicted?
maybe but I have lots of options and am having one hellofagoodtime  
Thanks

Maintarget wrote:I have a VTA ST-120 (465 hrs) with RCA 12BH7 in the out board positions and a sweet sounding Panasonic 12BH7 in the center, KT-120 drivers (300 hrs) biased up at .580V through a MAC mini using a Schiit Gungnir DAC (400 hrs) to Kilpsch Heresy speakers sounds sweet to me.
I have tried the following 12AU7s & 12BH7 Amprex, Bugle boy, Orange label, Telefunken, RCA Clear tops, Philco, Articus, Tung-sol, Reytheon, Philco, CBS, Siemens ECC 81, Sylvania JAN 587.
I originally started out with Sovtek KT-88 output tubes before switching to the Tung-Sol KT-120s as for rectification I'm currently using a JJ GZ34 and have on hand but havent tried a Weber copper cap WZ 68, Sovtek 5U4G and Sovtek 5AR4
Addicted?
maybe but I have lots of options and am having one hellofagoodtime  
Thanks

Put some ancient Mullard GZ-33s  into those rectifier holes but be sure to lie to your wife about what you paid for them.
Personally, I think Bugle Boys in the pre-amp and driver stages are over-hyped and over-priced. I would invite a flame on this, but I just don't think they're worth the gigabucks the tube-sellers are charging for them these days. Maybe I just don't like the Dutch sound.
The Weber copper caps do a pretty close job to the GZ-33s, IMHO, especially on summer days when the paint on the walls is melting. But nuttin' looks cooler (or runs hotter) than a pair of those big Mullard rectifiers in your stack, and they'll kill any flying insect that comes close.