I just spent a pleasant couple of hours experimenting with different clipping diodes at different gain levels. The results were more pronounced at max gain, which is to be expected - stronger signal = more clipping. My listening test mostly matches the measured diode forward voltages, with some exceptions which I don't understand (unless I didn't socket those diodes correctly).
I am too lazy to retype my notes here, so forgive the image:
According to the measured forward voltages, the yellow and green LEDs should have sounded much the same as red, but I couldn't get them to clip at all. I could neither hear clipping or see the LEDs light up.
I also tested asymmetrical clipping with a red LED and a 1N4001. I liked it the most. It had some of the openness of the red LEDs, but also some of the compressed fuzziness of the 4001s.
Interesting notes jug. What was your preference?
Build #1 - ST-1 - Completed
Build #2 - LP-1SS - Completed
Build #3 - TLA-1R - Completed
Build #4 - SGD-612 - Completed
Build #5 - ES-1G - Completed
Build #6 - STA-1HT | Completed
Build #7 - ST1JR - Completed
Current Build #8 - JBA-4
Build #9 - Semi-scratch build Tele x 2 - Completed
Current Build #10 - PRS-1H
Current Build #11 - AGJR-1 - Completed
Current Build #12 - ATL-1SB
Current Build #13 - GST-1
Current Build #14 - FBM-1
At the drive levels I normally use, none of the LEDs clip much in this pedal, leading to that switch position sounding the same as the diode lift position (a common observation I have seen of this circuit). I had to push really hard to get colours other than red to clip noticeably at all (drive knob maxed, guitar vol maxed, bridge PU, hard attack on power chords). So in this circuit, red LEDs are the only useful option to me.
I really liked the sound of the 1N4001s, and my favourite was asymmetrical with 1 red LED and 1 1N4001. That's what I left in for now.
Note the pedal has a 3 way switch that selects between 1N4148 clipping, no clipping (diode lift) and the LED sockets.
I also have more experiments to do, since the pedal has a trimpot to dial in the max gain setting of the circuit. I have a lot of upward adjustment on this that I could try to drive the clipping diodes harder. I don't want to lose the sweet low-gain sound though.
Note, I have vintage style low output pickups. Mileage may vary with high output pickups, or by putting a boost in front of the pedal.
Those are my preferred pups too.
Build #1 - ST-1 - Completed
Build #2 - LP-1SS - Completed
Build #3 - TLA-1R - Completed
Build #4 - SGD-612 - Completed
Build #5 - ES-1G - Completed
Build #6 - STA-1HT | Completed
Build #7 - ST1JR - Completed
Current Build #8 - JBA-4
Build #9 - Semi-scratch build Tele x 2 - Completed
Current Build #10 - PRS-1H
Current Build #11 - AGJR-1 - Completed
Current Build #12 - ATL-1SB
Current Build #13 - GST-1
Current Build #14 - FBM-1