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I’m intrigued by the new ’69 Stones board. How does it differ from the Guitar Bass Driver circuit, which is one of my personal favorites?
A bunch of stages for starters and as a result a different circuit.
The 69 is more about guitar tone than amp sim. The G.B.D. simulates the tube powerhouse amp as opposed to the the pure guitar tone of the Stones who used prototype SVTs on the Ya-Ya’s tour. Again the 69 breaks up like you would expect a guitar pedal to do and is all about that cranked air pushing tone without needing the volume. As a result you also have a lot of useful in between tones that the G.B.D. does not yield. Coincidentally this why the G.B.D. is a much better circuit for Bass guitar.
Two different monsters really 😉 I hope that helps.
Thanks Barry. I’ll just have to build one, then! But I do really like the GBD for guitar, too.
Also. What is the 10K trimpot for? Transistor bias?
Yes. See the schematic and that TR1 is connected directly to the Drain of Q5. TR1 adjusts amounts of resistance (10k) manipulating the Drain Voltage voltage at the transistor. This allows the Drain to be able to swing equally both positive and negative in response to the input signal. The rule of thumb is half the supply voltage, 4.5 to 5 volts. Most power supplies will measure slightly over 9v. Hence 4.5 to 5v.
Got it. Thanks!
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