Pamparo in Toronto

I’ve finally gotten the chance to look into building (modifying) the DIY expression pedal for my beloved Diamond Memory Lane. Props to the Diamond guys who actually included the schematic in the manual … see below:

Since it only controls how much feedback (number of repeats), I don’t find it useful to put a regular expression pedal for a couple of reasons:
- it’s bulky
- it’s unreliable in live situation

Having said that, I’ve modified the circuit a bit to provide 3 different levels of feedback (2 of which are controllable via trimpots)
- Feedback 1: 1 Repeat
- Feedback 2: 3 Repeats (by default)
- Feedback 3: 5 Repeats (by default)

Here’s the circuit schematic … maybe I should tinker with the “EXP POT” but I decided to leave that alone and modified the “TRIM BIAS” instead:

I have breadboarded the circuit and tried it … it WORKED!!!

Next step is to put it in an actual circuit board and an enclosure with some sort of LED indication of the setting. One potential problem is finding the switch to use without adding another IC to control it. I have not seen a lot of SP3T mechanical switches available … if you know of one, please let me know!