LOGAN 5 - Pseudo Ring Modulator

culturejam · Post by **culturejam** » 20 Oct 2010, 21:39

What would I do without Tim Escobedo, huh? ;D

A couple guys at the ILoveFuzz forum wanted to do a group build, and they decided on the Thing Modulator. So I volunteered to do a PCB layout. I named it LOGAN 5 because it sounds like some of the oddball music in Logan's Run. Not my cup of tea, but plenty of people dig the sound.

Here's the original schematic:
http://folkurban.com/Site/ThingModulator-709.html

I wasn't happy with the amount of noise from both the internal oscillator of the LMC567 and just general high-end hiss, so I made a few tweaks to keep it quiet. The result is less overall frequency range than the original, but the entire range of the Frequency pot is now usable (not noisy). The "Bias" trimmer is used to dial in the best compromise between overall output volume and circuit noise.

New schematic is below. Single-sided PCB layout and build guide are attached in a zip file just above the schematic.

One of the guys at the I Love Fuzz forum is doing kits for this if anyone is interested. I'm not involved with that financially, I just made the PCB layout.

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lolbou · Post by **lolbou** » 21 Oct 2010, 04:51

culturejam wrote:I named it LOGAN 5 because it sounds like some of the oddball music in Logan's Run

Ha ha, Logan... This is alow-cost car outsourced by Renault here in Europe...

But that's cool to see what tweaks you made...

Effectsiation · Post by **Effectsiation** » 21 Oct 2010, 17:31

Here's that IloveFuzz link for anyone interested:

http://www.ilovefuzz.com/viewtopic.php?f=44&t=12790

Dr Tony Balls · Post by **Dr Tony Balls** » 08 Nov 2010, 16:05

I messed around with this circuit on a breadboard the other day and wound up getting a low-level but constant background oscillation. Just a constant tone in the background. The effect was very cool but the tone made it not terribly practical. Has anyone built this circuit and can they comment on such a noise? Could it be a function of a noisy and unshielded breadboard? Or possibly the specific chip that I used is noisy/flawed?

culturejam · Post by **culturejam** » 08 Nov 2010, 18:13

I got very low-pitch "clacky" oscillation when I used a 100K Frequency pot. It was audible through a good portion of the pot sweep, but seemed to disappear from 15K down to zero. That's why I changed the value to B10K.

Also, I found that increasing the series resistance between 9v and pin 4 helps to reduce noise...as does adding a small cap to ground off pin 2 (output).

I built one on a proper circuit board using the above circuit, and it's actually really quiet.

culturejam · Post by **culturejam** » 08 Nov 2010, 18:23

NOTE:

I just updated the build guide with some additional mods. If you have downloaded the older version, please get the new one from the first post in this thread.