PWM how to switch between the lfo mod and the stock version

Solidhex · January 17, 2009, 06:10:13 PM

Yo

I've been gearing up to build Tim Escobedo's PWM pedal as featured on this page: http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html . Its a little more than halfway down the page. I love the sound of the LFO version but want to be able to switch it off and use a manual control so it can be used as more conventional fuzz too.
Can anyone recommend the simplest way to do this? I'm not knowledgeable enough about the way the circuit works to figure it out. I'm assuming in both version the .005 cap will be connected across pins 2 and 3 at all times right?
With the LFO, pin 3 is connected to the transistor collector, without its connected to a 500k pot to ground. That's one spdt.
With LFO, pin 12 is connected to the junction between the 500k pot and the 10k voltage divider. Without the LFO its left unconnected. That's another spdt.
Lastly with the LFO, pin 13 is connected to the junction between the 47k resistor and the 2.2uf cap. Without the LFO pin 13 is grounded. Yet another spdt.
I could accomplish this with a 3pdt but I'm guessing there must be a simplified way of doing it. Can the LFO just be disabled instead of being switched out completely?
Would be fun to have the LFO switchable with a footswitch. Almost like a built in psuedo phaser.
I searched for other topics on this subject but wasn't able to find any info about doing this specifically.

--Brad

slacker · January 17, 2009, 06:52:51 PM

I haven't tried this but I think it should work. Build it with the LFO and add a switch that connects pin 13 of the 40106 to ground, this will disable the LFO and make its output 9 volts. Now the 10k "depth" pot will set the resistance of the transistor connected to pin 3 and act like the Pulse width pot.

Solidhex · January 18, 2009, 03:58:32 AM

Yo

Thanks! it works perfectly. Just what I was looking for. The straight up fuzz from the circuit is pretty good. You can tame the glitchyness a bit sticking a lo pass filter in front of the circuit if you want it to have a smoother, more stable sound. I assume you could also exacerbate the glitchyness by sticking a high pass.

--Brad

Fuzz Aldryn · January 18, 2009, 07:53:14 AM

Hi Brad,

I suggest you're a busy man, but are you able to provide a layout for the circuit with the lfo? Had no luck finding a layout with the lfo, though I've found a bunch of without.
Would be great if you could post it here! Thanks!

Regards
Helge

Solidhex · January 18, 2009, 03:00:09 PM

Yo

I haven't got one finished yet but I'll let you know when I do...

--Brad

Fuzz Aldryn · January 18, 2009, 04:11:13 PM

Thank you Brad! I really appreciate that!

Regards
Helge

tiges_ tendres · January 18, 2009, 04:56:05 PM

I just worked this up. Not verified yet but looks ok.

tiges_ tendres · January 18, 2009, 09:10:14 PM

Quote from: tiges_ tendres on January 18, 2009, 04:56:05 PM
I just worked this up. Not verified yet but looks ok.

Verified! Well kind of. Change the orientation of the transistor and you are good to go. Although both orientations sound good, having the other way than on my layout yields the same effects as the samples from Mr. Escobedo's website.

Fuzz Aldryn · January 19, 2009, 05:58:52 AM

Cool, thank you so much! Considering this layout http://aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album18/FUZZ+PCB/PWM+PCB+LAYOUT.gif.html am I have to cut traces at pin 3 and 13?
Thanks again!

Regards
Helge

tiges_ tendres · January 19, 2009, 01:28:17 PM

Quote from: Fuzz Aldryn on January 19, 2009, 05:58:52 AM
Cool, thank you so much! Considering this layout http://aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/album18/FUZZ+PCB/PWM+PCB+LAYOUT.gif.html am I have to cut traces at pin 3 and 13?
Thanks again!

Regards
Helge

Just cut the trace at pin 13. Leave all that other stuff attached to pin 3 and add the lfo board to the 3rd pin.

Solidhex · January 19, 2009, 02:44:15 PM

Yo

I'm trying to get a layout together in Eagle but my library part for the 40106 Schmitt trigger chip skips pins 7 and 14! Since they don't show up in the schematic section and they don't automatically route themselves to power supply and ground I'm sort of stuck! Anyone know what's up? Might need to figure it out in a separate thread...

--Brad

e45tg4t3 · January 19, 2009, 04:21:46 PM

hi there,
solidhex you need to press the "invoke" button(4 little gates + a cursor, 4 buttons benaeth the "add" button)... then you need to ckick on the 40106 and than a popup window appears where you can choose the powersupply lines... click it press ok and tahn place it in the schematic^^... hope this will help ya...

Best Regards

Benny

Fuzz Aldryn · January 20, 2009, 10:21:38 AM

Hmm, should I wait for Brad's layout or should I try the way tiges had explained.... hmm.... cannot decide... Holy c***!;)

tiges_ tendres · January 20, 2009, 02:07:52 PM

Quote from: Fuzz Aldryn on January 20, 2009, 10:21:38 AM
Hmm, should I wait for Brad's layout or should I try the way tiges had explained.... hmm.... cannot decide... Holy c***!;)

If it helps at all, the longest part of the process for my version is stripping, tinning and attaching all of the wires. The rest of the circuit took maybe 20 minutes from cutting the board to getting ready to attach wires.

Way faster than preparing a pcb to be etched, followed by etching and then assembly.

Fuzz Aldryn · January 21, 2009, 09:55:12 AM

Nah, as I'm going and have to etch a board anyway this wouldn't matter. Also I'm not a huge fan of veroboards, as they seem to don't like me and I don't like them.

It never took more than half an hour so to make an etched pcb - I#m a fast guy with my drill, you know?

But thanks for your kind reply!!!

Regards
Helge

Solidhex · January 21, 2009, 10:31:42 PM

Yo

The layout is done thanks to Benny's tip about the invoke function. I can email the eagle files to someone if they want to post it. I'm not good with that stuff!

---Brad

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PWM how to switch between the lfo mod and the stock version