Hey,
Ive recently built a VCDO eurorack module and the main oscillator is weirdly crackling, kinda like a vinyl.
But the sub output doesnt crackle. I tried to switch the filtering stage, reflew some connections, tried a new jack socket. Nothing worked, it still crackles. Is that normal? Did anyone encountered the same problem? Should I buy a new VCDO IC?
Here is a video:
Thanks in advance, Matyas.
Is this the Electric Druid chip? I believe @EddyBergman had this problem due to the CV inputs and pots interfering with the analogue outputs. Is this built on stripboard? If I remember correctly Eddy built it in 2 halves with a grounding plane of foil in between the sensitive outputs and the rest of the circuit.
Yeah, sounds like it
Thats totally it. Well, i really dont want to rebuild the whole thing again, how can I at least get rid of some noise?
UPDATE: Ive removed some of the noise by just moving the CV wires to the back of the proto board!
But I can still hear some of the noise getting through. Thanks guys!
Is this a problem with the IC? I’ve got a few of these
From the link above:
I couldn’t get it to sound right so I wrote to Tom Wiltshire (Electric Druid) about this problem and here’s what he said about it
<Quote>
“It happened a bit on the first version of the PCB I did for the Frequency Central “Waverider” module. Eventually we tracked it down to the outputs being to close to the CV inputs. Keeping tracks and wires to those apart as much as possible helps a lot. On revision 2 of the Waverider PCB I routed the inputs on one side of the PCB, and the outputs on the other and that solved the problem. It boils down to noise getting into the CV inputs. That can come from many sources but from the chips own outputs was a big cause for us.”
<End quote.>
Yes this is a digital processor and they produce high frequency noise. Things you can do: Use shielded wires for all potmeter connections to the chip (except the 2 level pots). Keep wires between the two prints as short as possible. I used pinheaders to connect the two prints together which works very well. Use shielding between the CV inputs and processor print. Connect all shielding to ground. Shielded wires must be grounded only on one side. If you ground them on both sides you get ground loops.
One extra thing you can do is solder 100nF caps over the inputs on pins 1,2,3,7 and 8 to ground. When measuring with my oscilloscope I noticed a lot of spikes on the signals to those pins and the 100nF caps got rid of that totally. (Also see the text in my article about this VCDO).
Thanks Eddy! Really apreciate that.
No problem mate. I hope you get it fixed. This is really cool wavetable oscillator.