wsg wacky oscillator crosstalk?

stevebryson · Joined: Nov 15, 2014 Posts: 14 Location: San Rafael, CA

I just finished a WSG, my first MFOS project. It pretty much works and sounds wonderfully weird, but there is one thing that doesn't seem right.

Wacky oscillator A is as loud as the weird oscillators, even when the wacky too A switch is off. When that switch is on wacky osc. A is a little louder. I traced the signal with an oscilloscope, and it's where is should be when the switch is on, and everywhere after the switch the signal goes away when the switch is off. But wacky osc. A is clearly audible in the output when the wacky too A switch is off. It's hard to identify the wacky osc. A signal in the output with the scope.

Is this crosstalk? Is there somewhere else to look? The same thing is not happening with wacky osc. B, which is not audible when the wacky too B switch is off.

Weird minds want to know

wackelpeter · Posted: Sat Nov 15, 2014 5:40 am Post subject:

sounds like it's crosstalk between the wires... try using shielded cable for all osc Outputs with one end of the cable (the shield) hooked to gnd... usually ist prefered to use shielded cables especially when those wires are longer and tied Close together... that is recommended for most audio signals and square signals or generally siganls with higher amplitude and hard edges...

it's not a must that you always must use them but when there's some crosstalk it's the simplest solution... only negative aspect is that you would have to re-wire everything...

stevebryson · Joined: Nov 15, 2014 Posts: 14 Location: San Rafael, CA

Thanks, Wackelpeter. Yup, it was crosstalk. Moving wires around made it much smaller. Then I could hear that all the oscillators are leaking a little bit. I was worried what would happen with final assembly, but happily the wires in the box did not make the bad crosstalk come back. Rewire with shielded wire? Maybe someday…

But the WSG is complete and sounds great!

stevebryson · Joined: Nov 15, 2014 Posts: 14 Location: San Rafael, CA

Yes!! Crosstalk complete gone! Not being sure which wires carry audio signals, I replaced all but the filter control wires with RG-147 coax. Because my solder would not bond to the panel I ran bare ground rails from the ground connections on the pots, and soldered the coax shield to those. I have to be a little careful about how the wires go in the box, but done right the WSG sounds wonderful!

I strongly recommend this for all WSG builders.