which tubes to replace, where, and why

gmach

Member
My apologies if this is covered often. First, what is the rule of thumb as to which tubes (between preamp and output) change which aspects of tone? Next, how does one know which tube to replace among premp and/or outputs (V1, V2. . .etc. [by the way, I don't know what 'V' even means]).

My specific example: I have an amp with five 12AX7 preamp tubes and two 5881 (6L6GC) output tubes. If I wanted to take some harshness/brightness out of it, what am I looking to change?

Is there a nice website that would help me gain this type of knowledge?

Thanks.
 

gmach

Member
It is an Epiphone Blues Custom 30. I swapped the original Lady Lucks with Cannabis R's, and that made a world of difference. I'm now considering what might be done with tubes.
 

RussB

low rent hobbyist
TAD 6L6WGC power tubes. Very full, round sound with sweet break-up characteristics.

JJ ECC83S and/or ECC803S pew-amp tubes. They're great when you want a littlew less "edge" Get at least one of each, and experiment. Also try a Tung-Sol (new re-issue) 12AX7. Very nice sounding and reliable tubes
 

TweeDLX

Member
My apologies if this is covered often. First, what is the rule of thumb as to which tubes (between preamp and output) change which aspects of tone? Next, how does one know which tube to replace among premp and/or outputs (V1, V2. . .etc. [by the way, I don't know what 'V' even means]).
Is there a nice website that would help me gain this type of knowledge?
First off, "V" stands for "valve" (or tube). In a tube amp, you usually start counting with the tube furthest away from the power tubes. So, furthest away = V1. Usually V1 makes the biggest difference in tone, unless you have an old Blackface/Silverface Fender, and then it might be V2 (depending on which channel you plug into). Using a different phase inverter (the last tube before the power tubes) can make a difference, too. The other tubes all depend on the circuit/amp in question. Those TAD's do sound nice.

Mike
 

gmach

Member
Thanks, Russ and Tweed. I'll start with those TAD outputs and let the journey begin. I appreciate the responses.
 

ski_fast

Silver Supporting Member
For what its worth I just retubed my friends JMP Marshall. I put a blackplate 5751 in V1, a vintage Tung-Sol in V2, and a Sylvania 12AX7 with the huge plates in V3 (there are a lot of these on eBay now labelled Baldwin coming out of old organs). He had newer Electro-Harmonix 12AX7EH's in previously. Just the 3 preamp tubes completely changed the amp. It is tighter, clearer, ballsier, more defined. It now sounds like what you would hear on recordings. Very hi-fi. While some of the newer tubes are fine like the newer Tung-Sol, the old tubes from the 50's-70's are much higher quality. Better metal in the plates, thicker pins, richer tone. In my experiments running different different brands of tubes in all positions will give you a deeper thicker tone. As to your harsh, bright issue. The EH's were harsh and brittle in the Marshall. Old tubes will solve your problem.
 


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