PT80 Delay GGG fine adjust

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andregarcia57
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Post by andregarcia57 »

hello guys, i just finished my PT 80, the sound of the pedal itself is very good, however i am dissatisfied with the feedback potentiometer, is there a mod to work on the pedal with some kind of fine tuning? like in bbd's delays? some trimpot to add to this circuit? hugs
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stolen
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Post by stolen »

Hi!

What do you not like about the feedback pot? There's always trimmers that could be added - adjusting the 22k resistor that does from the taper of the repeats pot (via the 1uF cap) to pin 12 of the 571 would allow you to set the maximum value of the feedback knob. This load also bends the taper to be more "log-like"; a lower-value repeats pot (maybe 10k?) or a C-taper would give you more repeats at lower settings. But without knowing what you want it's tricky to give good advice here. If you want more repeats just reduce the aforementioned 22k resistor. For controlled self-oscillation either clipping diodes or some clever compander hacking might be interesting.

The trimmers in BBD delays are usually* for bias and clock bleed, the PT2399 doesn't need them and "playing with them" in a BBD unit only leads to increased noise and (quite harsh) distortion.

All the best,
stolen

*Sometimes there's a trimmer for insertion loss in flangers to fine trim maximum feedback, but we've never seen one in a delay unit.

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