[murf]

Hello Audio Experts!
  I am a mere babe-in-the-woods when it comes to tube rolling, but I would like to get beyond just using the recommendations of other people.  Sometimes these recommendations are vague, or don't address certain build features.  So I have a few questions!     I am asking specifically for use in an FV 400R amp (12at7, etc). 

1) How important is 'triple mica' over 2-mica?  My guess is pretty important since it controls micro vibrations.
2) How important are 'black plates' over grey plates?  My guess is not as important as triple mica, & maybe not v. important at all.
3) Is the getter shape important?
4) How close should the emission #s be, whether within one tube (balanced) or between two tubes (matched)?  My guess, pretty important to get proper channel separation & imaging.
5) How 'strong' should the tube be compared to new, or 100%?  Or, how low should I go?  My guess, the stronger the better!
6) Wing plates?  What the...?

TIA! Murf   

[I.Greyhound Fan]

Murf, the most important thing is how well it sounds to you and what you are trying to do with a tube.  For example, I like a warmer sound but want to keep deep bass, transparency, wide sound stage and even midrange with out sacrificing hi frequency resolution.  I have gone through several types of 6CG7's and settled on Raytheon black plates.  The thing is that tubes can have diffferent characteristics in different systems.  What sounds good in my system may sound totally different in yours.  Every one raves about RCA Clear tops but they don't work in my system.  The stock Electro Harmonix are way too bright and sibilant in my system.  I can tell you this though, in the new FET Valve Preamp and DAC the stock Electroharmonix sound great in my sytem, they are just not a good match for the Ultra II gear with my system.

To answer some of your questions, the type of getter has nothing to do with the sound from what I have read. I doubt that you can hear a difference in the type of mica or color of the plates.  The sound of the tubes was determined by the designer.

[murf]

Murf,
To answer some of your questions, the type of getter has nothing to do with the sound from what I have read. I doubt that you can hear a difference it the type of mica or color of the plates.  The sound of the tubes was determined by the designer.

Hey!  You mean to say, 'test' (myself) or 'trust' (others)?  Aren't there 'general' rules (ie: rules that can be broken), like "Hybrid amps sound best!"?   

Thanks Greyhound (not being facetious)   

Murf 

[oneinthepipe]

Call Jim McShane

[tonyptony]

Murf, I.GF is right on the money, unfortunately. To address some of your more general questions, however: You should look for a tube that tests close to 100% or better (if you're talking used or NOS - new current production tubes should not test "weak"), and it would be nice for the sections to be close and for the pair of tubes to measure close to each other (IME 5-10%). Having said all that, the tubes in the FetValve are not heavily stressed and the biasing will take care of some of the measurement differences. What will drive your search more is ultimately the sort of sound you're looking for.

Frank believes the FetValve design is relatively insensitive to tube changes. To some degree that's true. Compared to other amps and preamps I've heard, you'll find less of the sort of wild changes you'd hear going from one tube to another. But that doesn't mean there are no differences. I (and others here) have experimented and found the differences are enough to prefer one over another. What is preferred varies by the user. If you want a good sense (generally) of what to expect in the world of 12AT7 tubes, call Jim McShane like oneinthepipe suggested, and go to the Audio Asylum Tubes forum. Do a search for 12AT7. Read through the threads where AA member Bambi has a number of posts. In those threads you'll find Bambi and other knowledgeable AT7 users describe the qualities of many of the AT7s you may want to consider.

But live with the JJs for a while. They're not bad for stock tubes. You may ultimately wind up liking something else better, or find they are fine in your own system.

[murf]

Thanks folks,

I want to get some really good NOS tubes, but not at telefunken prices.  I'm sure these will cost a little bit, so I want to understand the significance of the terms thrown about.  The JJ tubes must be good if Frank sends his top amps out with them, but he has to use new tubes, & not NOS.  Getting into my FV amp is sort of a pain, so I don't want to do it often!  So I will take my time & try to be cool about it. 
I went to Jim McShane's web site but it doesn't have much info, and I don't feel good about calling him just to pump him for info.  The 'Bambi' search at AA does look promising....

Murf

[mark funk]

Look it this,

http://www.audiotubes.com/12at7.htm


                                                                                       

[murf]

Yes!  That Brent Jessee page is my main source of info at present. It stops just short of giving all the info I want.  But also, you know, "trust but verify"...he sells tubes, and his, even if good, is only one opinion.   

Murf

[avahifi]

We would like to see tubes that measure relatively high mu for their type.  It would be nice if they were matched channel to channel.  With the Fet Valve amps, we can advise that good old new stock Telefunkens bias almost the same as our JJ 12AT7s so no bias readjustment is needed.

Setting bias on the Fet Valve amps to accommodate tubes that are significantly different than the JJ ECC81/12AT7 type we supply is difficult and presents an electrical shock hazard.  We strongly urge you not to try this.  The issue is close by parts, such as extending metal heat fins, carry 200V DC or more. A short to ground here through you, or through the circuit can damage something.  If you want to try wildly different tubes, we advise that you return the amp to us to test them in circuit and reset the bias accordingly.  Bias setting is definitely not a do it yourself casual project.

Regards,

Frank Van Alstine,
 
PS, to our ears, different brands of 12AT7 tubes make nearly no difference at all with the Fet Valve amps.  They are used so unstressed and unloaded that normal tube differences just are not aggravated.

[trebejo]

There is some graph somewhere about some tube of some type showing some type of data about something having to do with electronics.

Now the specifics of that graph are what they are but the shape of the curve is what interests me. It is more or less a straight line in the region x1 through x2, and non-linear in the regions outside of there. The non-linear stuff is where things get interesting, but you may not be interested in listening to your amp under those interesting conditions.

Frank, what you are saying is that your amps always stay in that region, and therefore the tubes stay linear regardless of what brand is used?

[murf]

Setting bias on the Fet Valve amps to accommodate tubes that are significantly different than the JJ ECC81/12AT7 type we supply is difficult and presents an electrical shock hazard...  If you want to try wildly different tubes, we advise that you return the amp to us to test them in circuit and reset the bias accordingly.  Bias setting is definitely not a do it yourself casual project.

Regards,

Frank Van Alstine,
 
PS, to our ears, different brands of 12AT7 tubes make nearly no difference at all with the Fet Valve amps.  They are used so unstressed and unloaded that normal tube differences just are not aggravated.

Thanks Frank,
  That's good news in that I probably shouldn't spend big to get a nicer tube.  And in all honesty, the Sylvania tubes I tried (2-mica, black plate, 6679) sounded so much like the JJ tubes (strange looking 3-mica(?), grey plate) that the difference was inaudible.  But I did think the Siemens (ECC801s/E81cc, 2-mica, BP) sounded a little more lite & spacey,but with tight bass.  I think I liked them better, but still a very small difference. 
  But what would constitute a 'wildly different' tube (don't want to spend for Telefunkens)?   Can you give any preemptive hints?  (I will not touch the bias!  )

Murf

[tonyptony]

Setting bias on the Fet Valve amps to accommodate tubes that are significantly different than the JJ ECC81/12AT7 type we supply is difficult and presents an electrical shock hazard.  We strongly urge you not to try this.

I can vouch for this. I found out how it's done on the FetValve. Not for the faint of heart.

[Hydro]

From my experience with the FetValve amps: as far as nos tubes the '60's Mullard Gray plates are the best sounding of the 'reasonable' priced tubes. I sent Frank a pair when he rebuilt my 350 and he said that they biased the same as the new JJ's. Most of the other Mullards were too soft sounding for me. Siemen's 801's sounded about like stock with a little more clairity. As I have posted before, the cryo'd Genalex Gold Lion ECC81 is by far the best sounding tube both of my system's. You will be able to hear a difference. A little more etched sounding but the space in the recording is right on. They are about $90 a matched pair so they aren't cheap. I didn't like the way they sounded in my Ultra dac though. Preferred the JJ's there.

[jackman]

A couple suggestions...

I owned a Fetvalve and tried several different brands of NOS tubes.  In the end, the JJ's that Frank supplied sounded the best.  None sounded bad but the JJ's had the ideal balance of detail and quiteness.  Some NOS tubes were noisy or too soft.  Some were too bright or thin sounding.  The stock tubes that came with the fetvalve were the best sounding.  They were also the least expensive!

Lastly, if you want to try some NOS tubes be careful.  There are lots of fakes or you could wind up paying big bucks for unmatched tubes.  I recently bought some Genelex Gold Lions for my preamp (it's not an AVA) and got them from Jim McShane.  They were perfectly matched and sound awesome.  Very quiet and natural sounding.  For a bit more than stock tubes, the Genelex tubes are awesome. 

Give Jim an email and he will answer your questions.  He's a good guy and will not sell you something just to get your cash.  He told me to avoid NOS tubes and try these Genelex.  They are the best sounding tubes I have triedin my preamp.  I bet Genelex (the proper type) would sound pretty good in your aVA gear. 

[murf]

Hello Audio Experts!
Well, after checking the field out, I think I'll go with a hi-spec tube, such as 3-mica, Black Plate.  The last 2 tubes I bought as an upgrade were 2-mica BP, but with fancy label/names, like ECC801s (Siemens) and 6679/ECC81 (Sylvania).  Only the Siemens sounded any different than the JJ, slightly more open & airy. 
Old, 3-mica, BP, WA type, RCA or Raytheon tubes could be my ticket...maybe.
Does anyone (Mr. GreyhoundFan?) want to do a listening test on my reject tubes?  Postage is probably cheap.

Murf