I should point out that AVA hybrid equipment is not a good place to be fiddling around and experimenting. I found this out the hard way.
That sounds like a story worth telling for new FetValve owners like me. Let me say that I am NOT a tube roller - that's precisely a major reason why I did not want a tube preamp. Having spoken to Frank, I also figured that he already got the best sound he could after sleceting the tubes that he did for the FetValve. Please let us know what happened.
First of all, I was swapping tubes in an FetValve amp - which I later found out was not at all a good thing.
(You can swap tubes in a preamp, but not the amps.)
Beyond that, I'm not sure exactly what happened. I swapped some tubes in and out and the amp sounded worse than with the stock tubes. I put in another pair, turned the amp on, and one of the tubes flashed bright blue. That channel was dead and putting another tube in didn't help.
I sent it back to AVA and they fixed it for a small fee. I had evidently taken out a MOSFET in the front end.
I resolved to keep my nose out of the amp.
Frank has stated that it's ok to tube roll in the preamps, but not the amps.
Personally, I figure that you don't stand much chance of improving your preamp. The tubes that Frank sells are closely matched and tested. They're also ones that Frank knows will perform well for that application.
When you buy tubes anywhere else, you're not going to necessarily get that testing and matching. Even if they do test and match, and they testing and matching the right characteristics?
Furthermore, you don't always even know what you're getting. Let's say the stock tubes produce a gain of X in the circuit.
What will tubes that you buy elsewhere produce? If they're X-y they will make your preamp sound kind of mushy. (Lower gain is not a good thing in this case.) If they're X+y you are in good shape. Except.... how do you know whether they're higher gain, the same, or lower? What are those really expensive NOS, rubbed between the thighs of virgins, military grade 12AX7s? Will the seller guarantee they're higher gain?
Ok, that's just my take on it. I'm not a big fan of tube rolling at this point.
Now, guitar amps are different. They're actually musical instruments and the player can swap tubes in and maybe get just what they want. Poorer performance can be a good thing with guitar amps.
I think tube rolling started with guitar players, and people were trying all kinds of things. You might want to try old tubes in an old amp to try to get the same kind of sound your hear in old recordings. Somebody decides that whatever brand of tubes is wonderful and passes the word along. Pretty soon the price of NOS tubes goes from trash to 24K.
Also, don't forget that there were a lot of vendors who had bought big batches of old tubes that they had sitting around costing them money. They could very well be responsible for the perception of NOS as being "better." I know I'd try that if I were in that business.
