Muff's Modules & More

flts

i'm trying to get a simple plain analog VCO->VCA patch done with the waveform city. my intuition was that it would be done just by patching one of the analogue waveform outputs to the VCA in and taking the audio from VCA out as usual. the AR generator is normalled to the VCA control anyway, and i thought that inserting a cable to the VCA input would break the VCDO out -> VCA in normalization.

now, instead of getting the plain analogue waveform thru the VCA, that way i get something resembling a (VCDO generated?) square wave no matter which of the waveform outputs i patch to the VCA in. i think it is not the same as what VCDO is outputting either, but just a static square wave with no wavetable modulation to be heard. is this normal / intended behaviour or am i doing something completely wrong?

this is a bantam jack equipped model if that makes any difference (probably not) and everything seems to work logically as it should otherwise.

flts · Posted: Mon Mar 04, 2013 5:44 am Post subject:

To clarify further, the direct sin / tri / saw outputs are working fine - I get the right waveform when I patch directly from those. When I connect one of them to VCA in I just don't get the correct waveform modulated by the VCA at VCA out.

laserpalace · Posted: Mon Mar 04, 2013 3:57 pm Post subject:

Hmmm. Bantam shouldn't change anything. It sounds like your patch is right too. SIN > VCA IN2 should give you an attenuated output. I would say make sure you are patching into the VCA2 to break the normalization, are you possibly patching through the WAVE IN?

Edit - If this is a newer WFC with the latest legend then disregard the "VCA2". Another thing you might want to check is that you aren't patching into the VCA's VC control. The labels were a little confusing to me at first.

chamomileshark · Posted: Tue Mar 05, 2013 5:49 am Post subject:

odd. I seemed right to me and I've just checked it out.

Just patched sine, tri or saw into VCA < monitored via VCA > and I'm getting the different waveforms.

chamomileshark · Posted: Tue Mar 05, 2013 5:50 am Post subject:

sorry, just had one thought, turn the volume down - it's probably not the case but it it's cranked up you may be causing distortion somewhere else in your audio path.

flts · Posted: Tue Mar 05, 2013 2:57 pm Post subject:

okay, did some more experiments with the audio path, there's definitely something wrong or something i don't understand with the VCA. when i first plugged the module in i thought the VCDO sounded quite grungy and hardcore (which was a nice thing even though i thought it would've been different), but now that i took output directly from the WS OUT it the same banks sound nice and mellow (like i imagined they would). take output from the VCA and it sounds like same thing clipped to practically a square.

i confirmed my suspicions by plugging in an euro VCO to the waveform city VCA. same thing - direct out from euro VCO was a fine triangle, whereas output from the VCA (even at volume set really low) was basically a square wave at the same frequency. or at least something with MUCH more harmonic content.

so it seems like the VCA is clipping its input for some reason. any ideas why this would happen, what am i doing wrong? i've emailed wiard / cary (with a link to this thread) but if anyone sees something obviously wrong here, feel free to chime in.

using the manual volume knob (which gets really LOUD really fast) i've set the output volume to a level that shouldn't clip the following stages (they don't clip with the direct waveform outputs at same volume) so that's ruled out i guess. the voltage level is set at +-5 and the fact that the unit sounds normal otherwise should probably rule out me having plugged the power cable the wrong way.

laserpalace · Posted: Tue Mar 05, 2013 3:18 pm Post subject:

Are you monitoring your output through anything that would be causing the distortion? I'm sure that's obvious but in my experience the VCA never distorts or clips even when it's full clockwise.

Sounds to me like the VCA might be defective. I would probably just email Cary and see if she can identify the issue. She and Grant have both been extremely helpful when I was troubleshooting issues.

flts · Posted: Tue Mar 05, 2013 3:23 pm Post subject:

slow_riot · Posted: Tue Mar 05, 2013 3:44 pm Post subject:

if you have the volume on the VCA at max, and something is triggering the gate, the AR envelope normalised to the VCA control will push the amplitude into distortion.

flts · Posted: Wed Mar 06, 2013 1:41 am Post subject:

carygrace

flts:

I just emailed you. Sorry for the delay, somehow I missed your message when it came in.

flts · Posted: Mon Mar 11, 2013 2:43 pm Post subject:

No problem, situation in control! Guinness ftw!

flts · Posted: Sun Mar 31, 2013 7:32 am Post subject:

just had to update on this - the module had indeed broken (perhaps during its trip across the atlantic) and it was repaired by wiard.
w00t

jamb · Posted: Mon Apr 01, 2013 10:07 pm Post subject:

carygrace · Posted: Tue Apr 02, 2013 4:04 pm Post subject:

jamb · Posted: Tue Apr 02, 2013 4:09 pm Post subject:

Aha, yes I was certainly getting more than square.

Glad it's back in tip-top shape. Those DALEKS must've moved quick, or else the employees at the customs office in Finland are covert Daleks!

carygrace · Posted: Tue Apr 02, 2013 4:26 pm Post subject:

flts · Posted: Wed Apr 03, 2013 1:12 am Post subject:

hmm, no wonder the local customs office doesn't have a visiting address downtown anymore, i've had to handle all my business with them online now. makes sense...

just to make it perfectly clear: i don't think the issue was anyone's fault and no bad feelings whatsoever - the module was packed super safely and after i noticed the issue it was repaired super quickly. these things may happen during transit / handling no matter what. according to graham it was a cracked resistor somewhere inside the unit.

now to spend some more quality time with the wfc and save up for more hihi