Tweet
I need an opinion on something from people who know more than me. I just got a homebrew tube amp from a friend, who has done a few amps but no formal training. The amp had failed a long time ago and he doesn't even remember the specifics of it. It is odd that it has four power tubes but set up to be two pairs, each of which has a post PI master volume pot. He lost the schematic of it but described it as "Marshall model 1959 with post PI master for the inner pair and another for the outer pair of power tubes." Here is a 59 schematic without the PPIMV (https://ampspecs.com/marshall-1959slp-schematics/). He was running 6L6 in one pair and 6V6 in the other (same plate voltages, don't even know how high that is yet). I know that the JJ 6V6s can take really high plate voltages so he may have been running those.
My first thought was that this is pretty crazy, in that if the two pairs are driving at different levels they are going to be beating against each other (edit, not really against each other, but the "off" or "lower driven" pair seems like it will be seeing all of the swing from the more driven pair) on the primary side of the OT. But when I look at an amp like an Egnater Renegade (https://el34world.com/charts/Schemat...desch_8_09.pdf) they have something pretty similar, except that they only blend the two pairs, not give each of them independent master volumes.
He suspects that the amp failure was either the PT or the OT, as he got them from a source that he is skeptical of (they are pretty beefy looking transformers). Before I even check everything is if this dual master volume thing is something that can be done without repeated failure.
Thoughts?
Greg
My first thought was that this is pretty crazy, in that if the two pairs are driving at different levels they are going to be beating against each other (edit, not really against each other, but the "off" or "lower driven" pair seems like it will be seeing all of the swing from the more driven pair) on the primary side of the OT. But when I look at an amp like an Egnater Renegade (https://el34world.com/charts/Schemat...desch_8_09.pdf) they have something pretty similar, except that they only blend the two pairs, not give each of them independent master volumes.
He suspects that the amp failure was either the PT or the OT, as he got them from a source that he is skeptical of (they are pretty beefy looking transformers). Before I even check everything is if this dual master volume thing is something that can be done without repeated failure.
Thoughts?
Greg
Comment