So given the Lightspeed and Southland are basically the same circuit, I thought I might add a switch to swap between the two.
The switch does three things;
- Switches the hard clipping diodes in/out
- Changes op-amp gain (to account for the hard clipping diodes)
- Changes Drive pot resistance
While they use different op-amps, they're both just dual op-amps, so choose a favourite and run with it. The Lightspeed uses an expensive high-performance op amp, and the Southland uses a standard TL072.
Schematics for both can be found over at PedalPCB, if you want to check out the similarities yourself.
It's a little cramped now, but you can always add a row on the right-hand side to free up some space.
LIGHTSPEED X SOUTHLAND OVERDRIVE SWITCH MOD
Just built this one up. It's passing signal just fine but something seems amiss. It's pretty gated/splattery at higher gain settings.
ReplyDeleteDoes that happen on both settings (the switch)? I’ve not built this one myself yet.
DeleteThe odd sounding gating/splat is in both settings(at high gain). I will try the jumper fix here shortly. There was not a big volume jump between the two (orig layout) settings, so that's a plus. I'll report back my findings after the jumper fix situation.
DeleteI checked the layout and made a minor fix. The 1meg resistor on the switch was going nowhere, which would have affected one setting (drive pot value would have been fixed at 1meg, not switching between 500k and 1meg). Just need to move a jumper.
ReplyDeleteNot sure if that would have caused your issue. The rest of the layout looks fine to me. Hopefully I haven’t missed anything else.
After the jumper correction: The Lightspeed setting is pretty much as as I remember my previous build. The Southland side seems a bit gated/ unnaturally crunchy still (though I haven't built a southland previously to compare).
DeleteRight. Is it gated and unnaturally crunchy the entire way through the range of the drive pot?
DeleteOn the upside, if the light speed is sounding right, there’s only a couple of things to check.
As an experiment, try running the BAT diodes to ground and see what it sounds like.
Is the output level normal compared to the Lightspeed? As that’s one of the only other differences.
1) gain pot size difference
2) hard clippers (BAT)
3) op amp output gain.
The drive/gating occurs about halfway through the pot sweep on the light speed side, and the majority of the Southland side. The output level on both sides of the toggle switch are very similar.
ReplyDeleteI'm better at reading schematics than stripboard/vero layouts. If I wanted to try to run the BAT diodes to ground, would that be 15&16 by 9 to ground?
I might have to build this to test it. Probably not diode related if it happens in both sides.
ReplyDeleteShort the Bat diodes on row 9 to ground / pin 2 of the switch.
First of all thank you for this great layout. Has this been verified already?
ReplyDeleteHello - unverified, as I’ve not built it (yet) and someone has had issues with their build.
DeleteAlright. I am looking forward to it. Your idea to switch between these two pedals is great. Thank you! :-)
ReplyDelete