So I've started making a guitar-to-modular module, which should also work for bass. So far I have a preamp I'm happy with and I'm currently fooling around with the envelope follower. When that's done I'll add gate/trigger.
The preamp starts with a JFET stage. There's a lot of lore about that, the valve sound etc. Here are some sources:
The Don Tillman classic:
https://till.com/articles/GuitarPreamp/
Fetzer voodoo:
https://www.runoffgroove.com/fetzervalve.html
Tayda (all flavors):
https://www.taydakits.com/instructions/ ... onents--22
The majority of these circuits feed the pickup signal directly to J201 gate through a 33k resistor, mimicking Fender 12AX7 stages from the golden days. While this may be ok for single-coil pickups, I realized that most humbuckers will overdrive the JFET. So I added a 1M pot before the JFET to be able to turn down anything coming in. And there's a bright switch (which is always on![;)]( "wink")
The guitar audio signal is very dynamic, with short loud transients even when the overall volume is low. VCOs, on the other hand, are always going full blast. So I added a diode-feedback soft limiter which damps the transients and allows the gain to be cranked up without too much acoustic damage. There's a clip indicator LED, which helps in adjusting the gain so the overall output is clean ~10V PTP, with diodes clipping to ~16V PTP max - maybe a bit more but the opamps never saturate. Using something better than TL074 probably wouldn't hurt.
And here are some samples, both using a 4-quadrant multiplier:
Tremolo (I think it sounds much better with a 4QM than a VCA, because the phase gets inverted)
Ring-modulator (same setup but the LFO is cranked to audio frequency)
No filters or other effects were used.
The preamp starts with a JFET stage. There's a lot of lore about that, the valve sound etc. Here are some sources:
The Don Tillman classic:
https://till.com/articles/GuitarPreamp/
Fetzer voodoo:
https://www.runoffgroove.com/fetzervalve.html
Tayda (all flavors):
https://www.taydakits.com/instructions/ ... onents--22
The majority of these circuits feed the pickup signal directly to J201 gate through a 33k resistor, mimicking Fender 12AX7 stages from the golden days. While this may be ok for single-coil pickups, I realized that most humbuckers will overdrive the JFET. So I added a 1M pot before the JFET to be able to turn down anything coming in. And there's a bright switch (which is always on
And here are some samples, both using a 4-quadrant multiplier:
Tremolo (I think it sounds much better with a 4QM than a VCA, because the phase gets inverted)
Ring-modulator (same setup but the LFO is cranked to audio frequency)
No filters or other effects were used.
Statistics: Posted by dslamnig — Wed Oct 09, 2024 2:53 pm — Replies 0 — Views 59