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awesome, thanks- I'll give that a shot!

Just noticed that my (15V MN3008) Aquaboy DX build is losing 6dB from input to output. Sounds great otherwise.
Haven't boxed it up yet, no on-off switch yet so I'm not sure if this subjectively an issue yet, but with an input level of 6V pk-pk (about the limit before clipping), I have 8V p-p on the expandor output but only 3V p-p at the output of the board.
Is this typical? Could anyone advise how to add some makeup gain within the existing circuit?

Those are quite different chips, swapping them you may be replacing one problem with another, unless you are changing the power supply jumpers under IC3 to suit each chip as well.
When running the MN3008 (jumpers etc set to suit), did you have D3 in the circuit? D3 needs to be left out with the MN3008, otherwise there will be no delay.

Sorted

Expandor side is well biased now with a 10kOhm resistor at R37. Reduced the BBD2 output gain by reducing R28 and R29 to 33kOhm to stop the expandor from clipping so early.

Much more happy with the level of distortion now!

Thanks madbean, I can rebias the compressor side at Vcc=12V using R13/14, but would like to work out how to adjust the expandor side bias as well.
I am trying to get distortion levels at Vcc=15V as good or better than at 12V, which should be intuitive but for the expandor clipping I'm seeing with increasing supply voltage.
After looking through the NE570 datasheet, looks like R37 can be adjusted to change the expandor bias so I'll try that. To reduce the levels at the expander and stop the clipping I may just look at adding a small resistor at R27 or R55. I have noticed that repeats run away with the feedback knob at ~2 o'clock, even with the T1 trimpot fully CCW, so I can afford to throw away some signal.

Hi all, greetings from Australia!

I've just built up an Aquaboy deluxe delay (MN3101/MN3008)- it was a smooth build and the delay works and sounds pretty awesome, but even after calibration on a scope there is some residual distortion on transients that's a bit annoying. It actually improves significantly if I run the circuit down at 12V and re-bias the BBDs, even though BBD headroom is reduced. Pretty sure I've tracked it down to the compander biasing, but I could do with some guidance!

I followed the advice in the build instructions and socketed R13 and R14, but they seem to control only the "output 1" (pin 7) bias on the compander, and this can be adjusted to ~7.5V ok, but Output 2 (pin 10) is stuck down at 4.8V, and does not change when R13/14 values are adjusted.
Also, when increasing the input level (200Hz, sine) the first section to clip is at pin 10 of the compander, and it is assymetrical and sounds pretty nasty. If there is a way to reduce the gain in this section I think that would help as well- can anyone help me progress from here?


Many Thanks,