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So I picked up a fairly beaten up 1965 ac50. While it sounds pretty good I have a few questions other owners may be able to help me with.
First off before I take it to a tech (it seems to have seen a tech not that long ago based on new looking eh el34s and preamp tubes) I have a few tonal questions.
1) are the tone controls meant to work backwards and not really do much. From what I have read the tone circuits are almost the exact same as the top boost circuit of the time yet compared to ac30s and other top boost inspired amps) matchless, bad cat etc) the control work backwards and don't do alot. At either end there is the least low end, as you turn bass up it has a little on the brilliant and alot on the normal channel and about 3/4 then severely drops the bass) the treble controls just seem to cut, I can't seem to get that massive shift in mid range as I do on an ac30.
2) there seems to be a lack of bass on the brilliant channel, I know the coupling capacitor is responsible for this but it seems extreme much moreso then the amps that also have this (ac30, train wreck, z wreck, matchless etc) it doesn't sound thin it sounds nasal which brings me to point 3.
3) there isn't that much high end on the brilliant channel, I expect the normal to be dark instead with point 2, the brilliant channel sounds like it has a bandpass filter over it, all the treble control does is cut more, I wondered if the bright cap had been cut but it seems to have been replaced but still there. Even with pedals boosting high end on the pedal just adds more upper mids.. It's weird.
4) distortion is strange, it seems clean and then breaks up kind of abrubtly on low notes more like you get from a mic preamp or something, this is worse with lower gain tubes 12au7, 12ay7 but still present with 12ax7 if the input volume is low.
The other question I had is preamp tube bias for v1, is it. Biased for a 12au7 or did vox just put it in an ac30 biased preamp? If it is should I be using a 12at7 for more preamp gain.
Long questions, if there is a more vox knowledge base forum I can post in too I'd love to know
First off before I take it to a tech (it seems to have seen a tech not that long ago based on new looking eh el34s and preamp tubes) I have a few tonal questions.
1) are the tone controls meant to work backwards and not really do much. From what I have read the tone circuits are almost the exact same as the top boost circuit of the time yet compared to ac30s and other top boost inspired amps) matchless, bad cat etc) the control work backwards and don't do alot. At either end there is the least low end, as you turn bass up it has a little on the brilliant and alot on the normal channel and about 3/4 then severely drops the bass) the treble controls just seem to cut, I can't seem to get that massive shift in mid range as I do on an ac30.
2) there seems to be a lack of bass on the brilliant channel, I know the coupling capacitor is responsible for this but it seems extreme much moreso then the amps that also have this (ac30, train wreck, z wreck, matchless etc) it doesn't sound thin it sounds nasal which brings me to point 3.
3) there isn't that much high end on the brilliant channel, I expect the normal to be dark instead with point 2, the brilliant channel sounds like it has a bandpass filter over it, all the treble control does is cut more, I wondered if the bright cap had been cut but it seems to have been replaced but still there. Even with pedals boosting high end on the pedal just adds more upper mids.. It's weird.
4) distortion is strange, it seems clean and then breaks up kind of abrubtly on low notes more like you get from a mic preamp or something, this is worse with lower gain tubes 12au7, 12ay7 but still present with 12ax7 if the input volume is low.
The other question I had is preamp tube bias for v1, is it. Biased for a 12au7 or did vox just put it in an ac30 biased preamp? If it is should I be using a 12at7 for more preamp gain.
Long questions, if there is a more vox knowledge base forum I can post in too I'd love to know
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