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Fender Tremolo designs

7/14/1999 6:08 PM
SteveRFender Tremolo designs
Could anyone provide information about a number of Fender Trem circuits? Specifically I'm curious about the Super 6G4, 6G4-A, and AB763 designs.  
 
 
 
I've got the schematics and can see the topological differences, and have a vague sense of what they're doing, but would like a more in depth analysis or even just opinions of these circuits.  
 
 
 
First though...I'm not entirely sure I understand how the oscillator works!!  
 
 
 
From what I can tell the 6G4 and 6G4-A circuits basically use the oscillator to modulate a high frequency gain stage and a low frequency gain stage out of phase. The input signal is inserted and when boosted at high frequencies is attenuated at low freqencies. The oscillator seems to be different between the two circuits as well as the addition of the phase spliter stage in the 6G4-A circuit.  
 
 
 
Does the 6G4-A design merely have more gain and hence more "depth" than the other? And while the circuits don't appear to provide any real pitch/phase shifting they do seem to be attempting to simulate, to some degree, the effect of a rotating speaker horn. Am I oversimplifying this too much?  
 
 
 
The AB763 circuit would appear to be affecting both the OP tubes' bias as well as the signal level at the grid of the driver. My best interprtation is that this is the infamous mislabelled vibrato that really only provides tremolo, or amplitude modulation. the obvious advantage of this circuit being its single tube requirement as opposed to two or even two and a half. Aside from simplicity and economy, are there other advantages of this design over the others?  
 
 
 
Any comments on reliability, ease to set up and tweak, or sonic characteristics of these would be appreciated.  
 
 
 
 
 
Thanks.  
 
 
 
SteveR

 
Replies:
SpeedRacer My personal fave is the 6Gxx with t... -- 7/15/1999 3:50 AM