Re: amp vibrato (was: Little Walter was Re: throat vibrato)

[Markburness@xxxxxxx]

The Vibroverb,Tremoluxes & Princetons of that era (6G?) used the bias 
modulation to achieve vibrato/tremolo/wobble but this method only requires 1 
preamp tube. The 6G12 & 6G12A Concerts (as well as the 
Pro/Bandmaster/Twin/Super of the same age) use 2-3 12AX7 tubes to split the 
signal into highs and lows and and get them beating against each other.

The blackface AB763 Concert used the light dependent resistor found in most 
other BF & SF amps.

Regards, Mark.