Robinette AA1164 with tremolo and reverb deleted

[isaac_teller]

Hello. I've built this exactly as per the schematic with the addition of a passive efx loop between the 0.02 cap and the 10M/10pf(before the wet/dry split). When a pedal is used in the loop there is a significant power output reduction along with distortion. Is the 1M reverb load and 500pf reverb filter causing this? Thank you.


https://robrobinette.com/images/Guitar/AA1164/AA1164_Princeton_Reverb_Delete_Reverb_and_Tremolo_Schematic.jpg

[pdf64]

No, it’s the disparity in signal levels, between the insert point and the fx.

[isaac_teller]

Thank you.

[pdf64]

If you’re sure an fx loop (especially a passive one) would be beneficial, then the 3rd stage grid circuit may be a better insert point, as the signal level is about 1/8 of that at the 2nd stage anode. But the send impedance is even higher.
Or after the volume control.

[PRR]

....loop between the 0.02 cap and the 10M/10pf(before the wet/dry split)

I do not see a '10M'?

Guitar FX level is similar to guitar level, so you can use FX in the cord without a loop. Here V1 has gain of 50, tone stack has "gain" of 1/5, V1B has gain of 50.... there is gain of 500 from guitar to your loop send. No FX unit wants an >10V signal, and can't output that much. On the other side, the 3.3M:470k divider cuts-down whatever comes out of the FX unit. It's pretty lame by that point.

Signal at grid of 3B is like 0.2V, a pretty hot but plausible level for guitar effects. The 411k send impedance is a bit high to go far. Try the 3.3Meg:470k divider as 330k:47k for a more reasonable send. (Try with and without a 100p cap; length of Send cable will matter.) You should have a 1Meg grid-leak because you can't depend on FX to leak DC.

[isaac_teller]

I meant 3M3/10pf. I'll try the 330k/47k.