The Corruptor - CMOS Ring Modulator

[anotherjim]

This one
https://db.tt/c39i8Lba

The smaller the input R to a Schmitt trigger is compared to the feedback R, the more it acts like a zero crossing detector. The input from the first inverter is biased at the same voltage as the signal zero crossing. Any noise from the input can be interpreted as a signal if the Schmitt is too sensitive.
To suppress input  noise, you need the upper and lower thresholds of the Schmitt trigger to be at significantly different voltages above and below the signal zero crossing level. Too different, and it will be too insensitive and signal will drop out too soon in the note decay. So, it has to be some compromise. I suppose the 10k input R should ideally have a 50k trimmer resistor in series with it if you wanted to find the best value.

I'd also suggest that care is taken to keep the input signal path clean - screened cable all the way from input to stomp switch to jack.

[digi2t]

Ahhhhh, OK. Now I see. Another question...

In this diagram;



would the 10K after the second inverter have to be adjusted as well? This is the diagram that I used for the vero layout, but I've yet to play with it.

[anotherjim]

Maybe. On the face of it, the later version is more likely to get noise into the Schmitt due to more gain from 2 pre-amps. But it depends. I don't think Freppo has an issue with it.
At least we know a fix if it does happen.

[Freppo]

Hi folks
Here's a small update on my progress with this project

I have built the simple version on both vero and my own PCB layout, both verified.
As soon as I have boxed it I will put up the layouts and a demo video on my blog.

I did get sputtering on my PCB layout just as peterg did, so I changed R3 to 47K which helped.
It may be needed to change that on the sequencer version aswell... We'll see.

I have been trying to verify a PCB layout for the sequencer version, "the King Corruptor".
But both times I have built it up I get the same problem, the oscillator isn't working at all.
The LFO, envelope follower and the 4040 works fine though... I can't find any fault on my PCB layout.
Maybe someone else can have a look and see if I missed something?
Here's my PCB layout: http://parasitstudio.weebly.com/uploads/2/4/4/9/2449159/king_corruptor.pdf
I will put it up on the breadboard again just too verify the schematic... maybe it's not correct 

cheers / Fredrik

[Freppo]

I finally finished the barebones version of this ringmod.

vero and PCB layout can be found in my blog:
www.parasitstudio.se

I got the enclosure for the sequencer version prepared. Will finish boxin it in a few days.
/ Freppo

[blackieNYC]

Stopped about 15 seconds into the demo.
Your schematic on page 2, with the 47k change and the cap to ground with no switch,right?

[Freppo]

Stopped about 15 seconds into the demo.
Your schematic on page 2, with the 47k change and the cap to ground with no switch,right?

Yes, that's correct. The schematic I ended up with is included in the PCB layout PDF on my blog.

I should mention that i'm happy I had so much great input from anotherjim and from peterg that reported on his build.
Thanks guys!

[digi2t]

Following some corrections on the "King Corruptor" schematic that Frep sent me, I've updated the vero.



No drastic changes, just some off-board wiring shuffling. I also changed the 10K resistor on the input side to a 100K trimmer (VR 2). Just dial it to get rid of the oscillation, or, insert the 47K resistor here.

[Freppo]

Thanks Dino! Great work on the layout. It should be good now

I finally boxed it up. Here's a demo.

Maybe it deserves a new thread, so it's not confused with the original simple version?
cheers / Freppo

[digi2t]

All I can say is.....



2:07 to 2:13 sounds like doom. Reminds me of Escobedo's DOF, making out with an Uglyface. Everything else is pure insanity.

Daddy likes!

[digi2t]

It's done! All I can say... it's completely off the hook brothers and sisters. Here are the pics. Not my cleanest build, it's a bit of a spag monster, but it works fine.





I've updated the vero. Some minor corrections, and I also added a rate LED. You can run it directly off the rate pot, negative leg to the pot, and positive to ground. No resistor necessary. It only flashes when there's a signal output, which is kind of cool.



I'll do a video soon.

[Freppo]

Awesome!! So many LED's  Me like.
I think it looks really neat and tidy inside.

Which function is the second stompswitch? (sequencer on/off I guess?)

Looking forward to the video...
cheers

[digi2t]

Awesome!! So many LED's  Me like.
I think it looks really neat and tidy inside.

Which function is the second stompswitch? (sequencer on/off I guess?)

Looking forward to the video...
cheers

Second switch is as you called it, sequencer on/off. I preferred to have it as a footswitch, rather than a toggle. Not totally crazy about the wiring, but I must admit, cleaner than the Infinitphase. 

[digi2t]

Slight correction on the vero (wire switch on the fine tune pot). Here is the final product,

[blackieNYC]

Hi all
I've got a corruptor on the breadboard. Freppo has been most helpful - thank you. I'm using a 4049 instead of a 4069 which works if you address the change of pinout.  The oscillator and the guitar signal show up at the 1 and 2 inputs of the 4070 at a healthy 9v square wave, but the output at the pin 3 output is incredibly low but present.  10mv or so.  If I crank the amp, and put a cap straight to pin3 I can hear it and it works fine, just very low.
I discovered something - the 4049 is a 4049UBE.  Unbuffered.  I have one of these in a 49er distortion pedal, works fine.  Does the input of the 4070 not like the unbuffered output? I thought cmos played nice with cmos.  Additionally, when you look at the datasheets, you see what looks like the same output circuit on the equivalent circuit diagram.  Is there something I can insert as a workaround.  Don't have any buffered 4049s around. Nor 4069.

[duck_arse]

the 4069 is an unbuffered part, it comes no other way afaik but ibwb. the 4049ube should work the same.

[blackieNYC]

Figured out my (basic) corruptor problem.  4049s work just fine (again, mind the different pinout).  I tried 2 4070s, still didn't work.  I changed the wiring to use a different gate on the 4070, and it lives!  I either had two 4070s with one dead XOR in the same position no.1, or...  I have a bad spot in this extremely old breadboard, which has probably had even older resistors stuffed in it, with big fat 14 ga. legs.
Now it's great!
But, of course, there was a little sumthin' about the malfunctioning performance that I'm trying to recreate slightly....    Just can't finish a pedal!

[blackieNYC]

Awesome with a blend control! Somewhere around a 50/50 mix of the ringmod output at the output of the 4070 and the straight fuzz from the pin 1input to the 4070.   No additional 4070 gates seem neccesary.  Add a 100k branching off from pin 1, put that at one end of a 100kb pot.  The other end of the pot ties in just after the 100kb you see on the output of the 4070.  Use the wiper out as another Jim suggested on his add-on. 
I have found I like the 50/50 balance point so much I'm getting rid of the pot for a fixed resistor on a switch - 1for regular ringmod, 1 for ringmod added to straight 4069 fuzz. A 2nd pole of that switch changes that 22k res. in order to equalize levels when flipping between sounds. 
The blended sound is fantastic.  Fuzz with wacky artifacts, sometimes harmonious, sometimes not. Very musically useful, your note pops out from within this filth.  I think the key reason this ring mod works with a blend so well is the the oscillator and your guitar signal sound so similar, they are created the same way -each a crushed 9volt square wave courtesy of the 4069 essentially. It doesn't sound like a guitar sound and a disassociated ring modulator running alongside.  Reduced the cap to GND at the output to a little more highs.
Thanks Freppo!

[Freppo]

Cool Nice idea with the blend. I'm glad you like it!
/ Freppo

[Freppo]

PCB's are now avaliable in my webshop.

www.parasitstudio.se

There are a few other PCB's avaliable aswell and alot more coming soon, so please check it out.
Cheers / Freppo