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This pre amp uses 2- 12AT7 tubes for gain and 2- 12AU7 tubes as cathode followersI wanted to know if it makes a difference if all 4 tubes in this preamp ( the two AT7 and two AU7 ) should be the same brand ?
Do both gain and follower positions produce sound changes ?
If I use certain tubes known for say their clarity in the " gain " and the other two for tubes for say their warmth in the " followers" spot do they compliment/balance each others strengths?
So far I've put in NOS Mullards in the AT7 spots and left them in. I've tried a few NOS brands in the AU7 spots and have noticed changes in sound each time.
A member responded to this question with the response below my question to it would be if you can't "give back or add to sound changes further down the chain " than are my gain or my followers the the spots I would " roll tubes " ?RESPONSE FROM A MEMBER :Regarding one tube stage adding warmth one tube stage adding high treble extension for example... it does and does not work that way. Let me try to explain - My theory would be: a stage of amplification can only amplify the signal that is given to it. For instance, if you have a tube stage that completely takes out all high frequencies beyond 10khz, you cannot add another tube down the line that is known for high frequency extension and expect it to give back that extension past 10khz, or what was lost up the chain. It cannot add to something that is no longer there, once those frequencies are gone (up the line) nothing can give them back (in an analog world), it will only "color" what is still in the signal path. So, it's really a balancing act. Each tube is almost equally as important, as they all change the sound (some say rectifiers don't change the sound... but I would certainly disagree with that). But just know, if you have a tube that limits something early in the chain, you cannot give back what was taken away. You COULD for instance fool yourself into thinking you're getting back these things from other tubes/components down the line, but IMO it would only be in the form of distortion that you're leveling out your frequency response, or tonality to taste.
I know it can be annoying responding/talking about the basics and most may rather not waste their time .
Welcome to AudioCircle, bigsled!Using the same brand of tubes is not required. Yes, everything affects sound quality.Bingo! You have a good ear, and you are getting the hang of tube rolling. Better put your credit cards in a block of ice in your neighbor's freezer. I would agree with that. But don't worry, your brain can sort out what is lost and what is "gained" (<-- PUN!!!) Go by what sounds good and you'll enjoy the journey. A tube is only as good as it's circuit, so discount online tube hype where amps aren't discussed. Also, have some backup tubes and fuses on hand so when they pop you aren't waiting for parts in silence. It's always fun to help!! Let us know what you try and how it works out.
You're actually fortunate in that the AT is the most sensibly priced NOS of the three 12A*7s. The signal doesn't actually pass through the 12AU7s. I won't say they don't have ANY effect on sound but definitely not to the level of change of the ATs.
For audio I like low noise tubes what tube brokers rarely test.https://www.youtube.com/watch?v=13n1VCR6UXw