Elk Pro Sonic Schematic

[CJ]

worked on an old Japanese amp, kind of a Fender copy with bad oil filled Atlas caps that all need replacing,

note weird phase inverter that uses two different type tubes that have different gain, but the output AC signal seems to even out,

anyway, there seems to be no schematics available online so here it is>

 

[Whoops]

Nice,
thank you so much CJ

 

[abbey road d enfer]

note weird phase inverter that uses two different type tubes that have different gain, but the output AC signal seems to even out,

The trick with different anode resistors in the PI is quite common; it's there to compensate for the coupling between the two triodes that is not strictly 100%. It's supposed to reduce 3rd harmonic distortion, but actually it adds some!
Indeed sharing the PI between two tubes of different style is quite unusual.
The 6AQ8 is very different than the 12AX7, I wonder if maybe someone did an emergency substitution.

 

[CJ]

this Elk schematic is almost identical to the Pro Sonic only without the extra channel.

the biggest problem with these amps besides the bad coupling caps is the Piezo reverb pan,

looks like they needed the 12AX7 for reverb makeup, the 6AQ8 not having enough gain, they did not want to add half a tube so they just used the other half  of the 6AQ8.


weird resistor values also, 50K, 70K, 500K,

i wonder if people hot rodded these by simply moving the mains sw to 100? eventual meltdown would probably be the outcome.