Re: A100 reverb signal

[Dan Kerl <dlkerl@ro.com>]

Dallas Selman wrote:
> 
> Here's another one of those pesky theoretical questions that gets me out
> of
> bed and compels me to send mail.
> 
> The A100 has a separate reverb amp that depends for its input on
> a speaker level signal across the main speakers of the A100.
> Would the preamp level signal from the A0-28 drive this amp?
> And, if the reverb amp was connected to one "G" terminal and the other "G"
> terminal
> to an unbalanced leslie input (147), would that satisfy the criteria for a
> balanced
> signal output from the A0-28?
> 
> Dallas.....

I believe the AO-39 (main amp) drives the reverb tank (through some
current-limiting lamps). The output of the reverb tank is then sent to
the AO-35 (reverb amp, this number may be different on later A-100s).
The reverb amp provides no drive to the reverb tank. I doubt if the
AO-28 can successfully drive the reverb tank, as it is either a low
impedance load or (if not lo-Z) requires a substantial signal drive
voltage. Some power amplifier is still needed between the AO-28 output
and reverb tank input.

If the object is to eliminate the internal console speakers, you can
either keep the main amp and connect it to a 20W load resistor
(necessary to keep from damaging the AO-39 output transformer) or use
a small transistor (or IC) amplifier.

                                                Dan Kerl
                                                dlkerl@ro.com