Wave Multipliers build questions

creatorlars · Posted: Mon Jul 28, 2008 11:39 am Post subject: Wave Multipliers build questions

Hi everyone---

So I wired up and played with my CGS Wave Multipliers yesterday and am enjoying it. I am having a little difficulty knowing if what I'm getting out of it is correct/appropriate, though. The Grinder and Lockhart sections appear to be working fine, pretty straightforward...

The primary folder seems very touchy with where the controls are, before giving me any output at all. The offset, folds, and tri level knobs seem to have very limited, inter-related ranges -- sometimes a very small notch region has to be found before it will give me any sound at the output. It seems to sound right, and certainly mangles the waveform... but, it takes a lot of fiddling to find appropriate settings before I get any sort of useable/audible output. I built the full circuit with controls as detailed in the wiring diagram on Ken's site and have doublechecked the board and wiring, but am not sure where to look -- if anything is wrong at all.

Please let me know if you can share a confirmation as to whether this description of use sounds right or not -- I'm just curious. Smile

Thanks,
Lars

numbernone · Joined: Aug 16, 2006 Posts: 477 Location: new york city

I have a similar set of symptoms for the sqaure input and controls. Very small regions wherein any sound passes. What does pass sounds great, however its definitely not as usefull as it could be. I have spent a little time mucking with it, but tend to get caught up in using the triangle input and forget about getting the square in shape.

I resoldered some questionable connections early one which got me to where I am now. I would say break out the magnifying glass and good light and go over it very closley top and bottom. I will check my notes tonight and if anything seems reasonable to your situation I will post it.

I have lots of module maintenence needs right now!

creatorlars · Posted: Mon Jul 28, 2008 12:17 pm Post subject:

Yeah, I've resoldered and checked any questionable connections with the meter... I could be missing something, or maybe a chip is out or something?

Just not sure where to begin looking, because I'm not even sure if it's broken. Smile

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

Is your input signal strong enough?

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

Mmmm. I've barely played with mine since completing it, with all of it's options. I remember though (this is back in November or so), that when I turned one control (Pulse Width, IIRC), I would get a strong detuning from my oscillator hooked up to the wave folder.
I haven't yet though, gone through and checked everything. Also, my 3 VCOs at the moment, are only putting out Sawtooths as I still have to build my waveshapers (which will be separate from the VCOs, for more flexibility.)

When I go to investigate the module overall, I'll check for any similarities and report on any fixes that I make, if required. Smile

My Grinder and Lockharts are fine though and were sounding wonderful, again, IIRC. Wink

creatorlars · Posted: Mon Jul 28, 2008 9:40 pm Post subject:

I'm feeding it with a 10v peak to peak VCO, so I'd think the signal should be strong enough. Is there anything else I should look at?

Thanks for the responses!

I played with it a while this evening and had some fun with it, but there are definitely points where it's easy to lose audible output

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

Try increasing the value of the resistor between the wiper of the pots and the rest of the circuit, thus de-sensitising the controls.

Ken

creatorlars · Posted: Tue Jul 29, 2008 9:07 am Post subject:

I will try that, thanks Ken!

I'll also post some sound samples, too. I guess a weird thing is that the output seems to be kind of instable and maybe clipped? It seems to fluctuate a little, even without any CVs patched in.

I'm also hearing some bleedthru between the primary folder and lockhart outputs. The Grinder seems perfect/sounds awesome.

I just got a beefy new Power One supply, so I don't think that's the issue.

I'm still a little confused -- should it be possible to "lose" the signal at the output entirely, like what is happening to me?

ericcoleridge · Joined: Jan 16, 2007 Posts: 889 Location: NYC

creatorlars,

you've probably seen these clips on the metalbox site, yeah? there are audio examples here from various outputs on the wavefolder:

http://www.metalbox.com/modules/wavemult.html

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

You shouldn't be seeing either instability or bleedthrough.

Are your wires bundled together? If so, separate them.

If you drive it hard enough, it would eventually clip, but the only part that would get clipped is the big triangle that forms in the middle of all the folds.

creatorlars · Posted: Thu Sep 04, 2008 8:49 am Post subject:

Dumbass Update: After beating my brain against the wall over this for the past couple months, I pulled the board back out one final time to inspect it next to the PCB diagram on the website. There was a single reversed diode. That seems to have fixed my issue! I get the expected sounds now, and it sounds awesome, but haven't played with it enough yet to really know if I'm 100% there.

Smile

creatorlars · Posted: Wed Dec 03, 2008 12:28 pm Post subject:

A quick update on my Wave Multipliers. The main multiplier is still having some stability issues. It seems to be working fine for a few minutes and then the output drops entirely or intermittently. I've been over the board and wiring dozens of times and have no idea what's going on here. Any ideas? I'm about ready to just order another PCB and rebuild it from scratch, but it seems like I must be missing something simple.

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

Check around the VCA - the LM3080 or CA3080. That's the only thing I can think of that would change levels.

Also if you have an osilloscope, check that none of the stages are going into high frequency oscillation. A 47pf cap between the output and inverting (-) pin of each op-amp would stop that.

creatorlars · Posted: Thu Dec 04, 2008 8:26 am Post subject:

Thanks Ken! I'll check out the 3080 and try a different chip there too -- I have had some bad 3080's in the past, but never thought to try a different one here.

What exactly am I looking for on the scope with the HF oscillation?

Cheers,
Lars

otherunicorn · Joined: May 11, 2008 Posts: 136 Location: Australia

With no input to the wave multiplier all of the op-amp outputs should be at a DC level (shold be 0Volts). If you find a waveform here - often up in the megahertz range, the op-amps are oscillating. This is cause by stray capacitance. Adding the 47pF caps as described stops this.

creatorlars · Posted: Mon Jan 05, 2009 9:23 am Post subject:

Whew. It's fixed! I replaced the 3080 and found a bad solder joint near one of the op-amps. I -knew- something was wrong, because it sounds completely different (and amazing) now. Thanks for taking the time to help me troubleshoot this.