I'm converting a Muzak PA amp for guitar, basically just redoing the power supply and adding a dual triode 12ax7 preamp and vol/tone controls ahead of the 7199 -> 6V6PP power amp.
It's a cool looking PA - pics are here.
I haven't been able to figure out the purpose of the 400ohm 20-wall resistor is between the PT's center tap and ground? If it's too small to read,
the schematic says "Connect Jumper for 8 Watts" next to a dotted line in parallel with the resistor. I've searched a number of forums and can't figure out what it's doing there.
Schematic is below. Thanks.
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It's a cool looking PA - pics are here.
I haven't been able to figure out the purpose of the 400ohm 20-wall resistor is between the PT's center tap and ground? If it's too small to read,
the schematic says "Connect Jumper for 8 Watts" next to a dotted line in parallel with the resistor. I've searched a number of forums and can't figure out what it's doing there.
Schematic is below. Thanks.
I tried that once, to reduce B+ voltage and heater voltage in an attempt to keep tubes from burning up. It made the whole amp sound loose and woolly in the bass. If you think about it, that's basically adding extra impedance to the power supply, reducing damping. It could be a nice effect for a guitar amp. The clean sound would be 'juicy' and not tightly damped on the low strings, if that's something you're looking for.
Thanks. Suppose I could leave it in there for the moment and see what effect it has. If it's something cool I could make it switchable bypassed/not..
JR
JR
Presumably in normal use it's switched out anyway, as it will seriously reduce output power. 'Possibly' it's for giving a low power 'practice' setting?.
Muzak is a provider of background music for restaurants, offices, and other businesses. The needs of a larger restaurant might be for more power than something like a dentist office. So reduced power makes sense in those cases.
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