Date: Wed, 12 Feb 2003 03:12:10 EST From: Markburne~ol.com Subject: Re: amp vibrato (was: Little Walter was Re: throat vibrato)
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.