Hi guys,
I have come across two things that make me wonder if my synth is working properly.

So far I have followed assembly instructions to a tee. R6.1 has been wired to ground instead of S2 as detailed in the June 11th connection diagram update.
My only modification has been the replacement of the mono Synth Out jack with a stereo switching jack. The new jack has been connected as the old one was but with a wire joining the left and right output pins. The switch is not currently being used – I just wanted the option of installing a speaker in the case at some point.

During final testing I noticed:
1- Volume pot R9 only affects volume within the last .5cm of CW rotation. The output is silent until the control reaches this point.

2- OSC 1 Pitch pot R12 only affects sound within the last quarter turn of CW rotation, and cuts all sound at full CW rotation. The LFO LED blink rate also slows slightly within the last 2cm of CW rotation.

These two symptoms seem to be consistent regardless of how the other controls are set. Aside from these issues the synth makes some great sounds and all other controls seem to function as expected.

I would appreciate any troubleshooting tips you can offer. Tonight I will replace the original Synth Out jack in case I screwed things up by doing this.

Thanks for your help,
Tim

Hey, I think everything is working as it should… the ranges on the knobs could use some work. When we do the next pcb run we’ll try to address the ranges a bit. In the meantime, depending on into circuitry you are, you could put some resistors in parallel to adjust some of the ranges, I’ll have to get back to you on just how to do that.

There’s actually quite a bit of magic in the circuit… for instance, the LFO knobs affect the sound even when the LFO switch is off. A small bypass cap across the power and ground of the 555 would address this, but when we tried that it took away from the character a bit. So, just trying to say that there’s some unexpectedness in how some of the knobs work, but they should all definitely do something, let us know otherwise, if you think something’s still off.

OK thanks Scott, that’s the sort of answer I was hoping for.
I enjoy working with electronics so I’ll grab some resistors and see if I can tweak the ranges a bit. If I find something that works I’ll post back.
The unpredictable nature of this circuit is very appealing to me so I don’t want to do anything that might kill the mojo…