QUESTION about Installing "Matched" Tubes

I go with the transconductance value if I can. Plate current works too but IME is less accurate.

You'll have to bias the tubes up anyway, but if they all show the same transconductance values the bias setting will be nearly the same on all of them. But the thing is, what the tube is doing at half and full power is important too. That is why I go with transconductance.

Thanks.  Well, after yogiboy's post I just slammed 'em in there and biased.


Atmosphere, maybe after a listen, tomorrow I'll re-arrange them.


So for each 4 tubes per amp, I just select the transconductance with the closest value number, correct?

Yes

Mercy, they aren't matched that well prof. That's for darn sure. If  within 15% is matched.. You're ok..  You want to match the first number and the second number is what is left in the tank.. pretty simple..

You want those to be in pairs to.. I'd have to see how CJ wired the power valve side, but v1,v2 and v3,v4. CLOSE.. the 46.8 is NOT matched... The numbers don't lie.. No matter how you arrange them the ONE will be over 10%.  It should be 5% MAX... That's if you like matched valves.. 10% is what Golden Lyon call matched.. 5% was the GE (Tung Sol) way..

YES they make a difference in SQ.. Either at the beginning of the valves life or the end, BUT not all of the valves life.. That is why we MATCH even with auto bias.. Just SLOPPY not to... Where we don't lose SQ we lose a LOT of time between valve changes because of ONE valve taking a dump..

Especially for the cost of NOS Matched.. LOL One set is good, though.

Looks like numbers from a Maxi Maker.. I own one.. Great testers..

Regards

Hi oldhvymec.   (And others...thank you!)



Yeah, I was wary of that one number being extra high.  That comes from a replacement tube.   I'd bought two matched quads, but one tube turned out to be bad, and I guess that's the best replacement the proprietor could find.


Another thing:  I'm surprised at the nature of the change in sound this brought to my amp. 



Up until how I'd stuck with whatever CJ recommended at the time, which 6 years ago where the modern Tungsol 6550s.   So that's what I'd used until recently.  I started hearing creeping grain/distortion in my system and figured it was likely tubes.   I've had the CJ Premier 12s since the late 90's and never replaced the small input tubes either!   So I figured it was time just in case.  The original were GE tubes, one 5751
two 6FQ7 per amp.


I ordered the Svetlana Winged C 6550 NOS tubes, and wanted to try tube rolling for the input tubes.   Bought these:


5751 super low noise:


http://www.tubeaudiostore.com/57suplownois.html


And these Mazda 6CG7 / 6FQ7:


https://upscaleaudio.com/products/mazda-6cg7-6fq7


My research on the Svetlana Winged C 6550 NOS tubes suggested they had a rep as a linear-sounding tube, tight bass etc, not overly tubey.Which I was kind of going for.


The results have been, first off, a total lack of distortion and grain, so that problem was fixed.  Utterly gorgeous, smooth, velvet texture and tone.


BUT...an increase in the "tubey-quality" - the bass is less defined, bigger, a bit woolier, less air on top, a teeny bit thinner upper midrange.  And most of all a mellowing of dynamics, punch and density.  In effect it now sounds more like a slightly underpowered tube amp - gorgeous in tone, but lacking some drive and aliveness.   That part is a bummer.


So I'm wondering if it's the 6550s or the input tubes changing this character.    I've heard input tubes can change an amp even more than the bigger output tubes.


Thoughts?  (Anyone?)