Happy new PWM circuit

Earthscum · January 01, 2012, 03:38:47 PM

Actually, I'm really digging on this one BECAUSE it works with bass... I've got concept schems of all varieties that are so much more complex than this to achieve the same thing. Every single one has been based around the PWM being controlled by CV as well as a F-V converter to immediately vary the width a bit wider on the low notes.

Funny thing is that I mistook the transistor stage as a phase splitter stage until Teeth mentioned the need for the 220n to "Gnd", not what I thought (btw, that really is a nasty sound that 220nF gets rid of, isn't it? Uck). I kind of expected the circuit to work like that (actually hoped, not expected), but was completely based on a short-term idiocy, lol.

electricteeth · January 01, 2012, 09:53:21 PM

I play bass and design all stuff for that for the most part! SORRY! FORGOT TO MENTION! A darlington really works better? I thought the switching would be too slow or something... ...it might be a good tradeoff for more stable voltages. I think it really depends on the bass you are using as well. I have a single bridge humbucker bass thats real close to the strings, it works great with this effect on all strings except for the E. Maybe since your bass reacted much differently from string to string it would be good to design some filter sweeps at the input. I will get to work on a resonant bandpass filter so that you can easily select frequency range. The 220n to ground is vital. so much highs get cut with that and it confuses the 555555555555 too much. Glad this circuit is liked. I want to make a heavy duty version of this that uses an integrator (possibly) to create an accompanying saw/tri wave and cutoff filter. NEED A NAME FOR THIS CIRCUIT BTW!

Earthscum · January 01, 2012, 10:30:24 PM

I play Ibanez GSR 205, pair of stock jazz pups. Fairly average as far as output goes.

I've become a big fan of darlington transistors (MPSA13 in particular), NE5532's, and MPF102's for bass circuits. D's and the 5532's have, to me, a certain clarity... and they are pretty quiet devices, too. MPF102 jfets just have a certain darker tone to them, in certain circuits, that gets me just right.

So, since I had a darlington in front of me I figured I'd try it out. You might get some super sweet touch-sensitivity from it, since you're running the hb's. I tried a 2N2222 first, couldn't get more than half a second of sustain. 5088, modified a little, a bit better, but the A13 seems to be pretty decent. I just rebiased it a little. I gotta plug this back in and play with it some more, since I can't seem to find a single mosfet in my collection of crap to try out the Hells Gate/Tranquility Gate stuff.

electricteeth · January 01, 2012, 10:47:53 PM

Nomes are good transistors but straight 900hf trolltec trannies run the best with this circuit! Its in the cylinders. The filter bearings on the caps really matters as well.

I think an opamp is really where its at for the trigger input. I ordered my enclosure with a second stomp switch. Im rebuilding the board without an amp on the input so that i can run other (non guitar) stuff into it. I plan on building an opamp booster (which should power the circuit with passive instruments). The second stomper will toggle the 220n on and off and an led. That way you can kill or activate that horrible octave sound. I find it is groovy on faster punk stuff. A ldr would be neat in place of the "width" pot. Call me a sucker but I love LDR's on the tops of my pedals. I have a devi ever feedback looper with ldr on its face and it makes the pedal. I have another pedal that it sucks on as well. Might work. My next project is using an ldr.

DavenPaget · January 02, 2012, 01:16:00 AM

Quote from: electricteeth on January 01, 2012, 09:53:21 PM
I play bass and design all stuff for that for the most part! SORRY! FORGOT TO MENTION! A darlington really works better? I thought the switching would be too slow or something... ...it might be a good tradeoff for more stable voltages. I think it really depends on the bass you are using as well. I have a single bridge humbucker bass thats real close to the strings, it works great with this effect on all strings except for the E. Maybe since your bass reacted much differently from string to string it would be good to design some filter sweeps at the input. I will get to work on a resonant bandpass filter so that you can easily select frequency range. The 220n to ground is vital. so much highs get cut with that and it confuses the 555555555555 too much. Glad this circuit is liked. I want to make a heavy duty version of this that uses an integrator (possibly) to create an accompanying saw/tri wave and cutoff filter. NEED A NAME FOR THIS CIRCUIT BTW!

Jigasaw'm

Keppy · January 06, 2012, 08:05:54 PM

Quote from: Earthscum on January 01, 2012, 10:30:24 PM
I tried a 2N2222 first, couldn't get more than half a second of sustain. 5088, modified a little, a bit better

I just breadboarded this with a 2N5089 and had the same sustain issue. Only low notes came through (playing a Strat) and no sustain. I tried an opamp input stage and couldn't get it working. Went back to the 5089, still not working. Hmm... Does it take much to fry a 555?

electricteeth · January 06, 2012, 10:01:22 PM

I doubt you fried it. I'm going to go back over this and rebuild it on the bread and get it more stable. The opamp stage should have been an improvement though. Sometimes opamps take a little tinker to get going.

Keppy · January 06, 2012, 10:20:03 PM

The opamp stage was fine (I audio probed it). This is my first use of a 555, though, so I don't know if my link from the opamp to the 555 was done properly. I just ran the output of a 10-100x gain stage through the coupling cap into the trigger pin. I wasn't terribly surprised I didn't get it working, only that when I went back to the 5089 that I couldn't get back the results I had in the first place.

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Happy new PWM circuit