Friday, October 19, 2018

Zener Synth Distortion: alive and kicking (with sound file and scope photos)

Hello Again.  This time closing out the "Zener Synth Distortion" Project.

You can read Part I, how I stumbled upon this circuit, here.

2x zener prototypes, each slightly different builds, are up and running,  panels Lazertran'd, ready to go.

This is a super simple build, almost no parts!

How does it sound?  you be the judge! I have uploaded a demo sound file on Soundcloud.

I tried to give the most objective before/after demo of the 2 modules I could. No reverb, no filters, no echo etc. boring right?

Here is how I patched my fully DIY home-grown-works-almost-all-the-time modular synthesizer to get the demo sound going:

On the demo the first few sounds are from the "Zener" design:

"Zener" provides in your face, loud, crunchy distortion and greatly emphasizes beat frequencies.  maybe a bit much?

The rest of the demo (the last 3:30 or so worth) is "Son of Zener", a lot more subtle.

Shorts anyone? On "ElectroMusic" forum there was discussion about buffering the inputs (so 2 input signals don't go through both inward facing zeners and short one another).  Ach Tung!  I added a single unity gain buffer to one side of each design.  Update: After a bit more discussion with Phobos from the site, it makes sense to buffer the Son of Zener input as well, since the transformer only supplies about 45-50 ohms of resistance.

Another thing that came up on the forum: what do these distortion doodads look like on a scope?  My Siglent save to USB stick doesn't work (Firmware issue?  Damn!  Says save, then nothing on the stick!) so excuse the crappy photos, but here it is:

Source waveforms look like this of course:

Mixed, through ZENER they look "square waved" as you might expect (note the DC offset--you may want to get rid of that if you build this circuit--cap coupling should help, but me? I fix it soon....)

But other times you get messed up sine waye craziness......

In case there was any doubt, it's not true ring modulation; again I think the circuits beef up any beat frequencies, sometimes they jettison the fundamentals entirely, so you get oddness (hear it in the demo?) end up with something that reminds me, sometimes? a bit?? of ring modulation.  And I can't figure out why the transformers are necessary, from my limited knowledge of inductors, they shouldn't be, but trying these designs the bench without them yielded less "effect" for things like the pseudo R-M sweeps.  Sorry, i  can't say why....

OK that's it, time to move on. I can fab a PCB of this if anyone is interested; I can't charge you for 'em, sell em on etsy or whatever, due to the deal I have with my current employers, but I can send a "freebee" out to whoever is interested (help me w/ postage?  Whatever....)  If there is any interest I'll get that going. Until then enjoy some Ziener for your wiener.....This is a super easy circuit and I'm sure can be improved.  Different value Zeners?  More buffering?  Figure out if the transformers are needed or if I was listening to too much 80's pop while I was prototyping? How about an AC offset in front of each input (which changes the sound).  Please let me know whatever you come up with. Have fun!

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