Build was based around an AB763 circuit. Hoffman Eyelett board and parts from their AB763 2 channel kit. Classictone Vibrolux size Power Transformer model 40-18041. Hoffman Super Reverb size Output Transformer.
The Vibrato Channel is stock to AB763 spec.
I added a 100k Negative Feedback pot on the back of the chassis. As you roll it up you reduce the amount of negative feedback, which increases gain and how 'raw' the signal is.
I implemented a number of mods from Rob Robinette's AB763 mods web page: https://robrobinette.com/AB763_Modifications.htm.
- Fritz mod to add reverb and flip phase of the normal channel
- I tweaked some values in the tone stack via the lead channel mod:
V1A Cathode Resistor - 2.2k
V1A Bypass Cap - 1 uf
V1B Coupling Cap - .001 uf
V1A Load Resistor - 220k
I also messed with the tremolo quite a bit. The Hoffman kit comes with a 6G16 style power tube bias wiggle tremolo circuit. But I had some difficulty getting a lot of depth in the tremolo. So I added the mods listed on this page:
http://el34world.com/Forum/index.php?topic=604.0
I also experimented with the insertion point. In this video I have it setup to insert on the cathode of v1 and v2 - similar to a Vibrochamp style tremolo. Still working on it as it doesn't sound quite right to me.
Hit "Subscribe" for more videos!
http://www.youtube.com/subscription_center?add_user=kleydj13