Author Topic: Fuzz with 2 lm386 chips?  (Read 3023 times)

thejoe

Fuzz with 2 lm386 chips?
« on: April 21, 2018, 01:01:11 PM »
I built the simplest of 386 fuzz circuits and I'm trying to put a second 386 after it. Maybe it'll be absolute garbage. I have it going straight from the output of ic1 to the input of ic2 but there is very little signal. Pins 1 and 8 are open on both.  If I remove power from the second chip, the signal is passing through at a great level. I tried putting a 10uf cap between 1 and 8 on either/both chips but it isn't doing much.
Could the problem be that both chips are pulling from the same 9v source?

Thanks in advance.

Marcos - Munky

Re: Fuzz with 2 lm386 chips?
« Reply #1 on: April 21, 2018, 02:08:05 PM »
Sounds like a short somewhere on the 2nd circuit. If you remove the power from the 2nd chip, you should get no sound.

It'll be helpful if you post the schematic you used and a few pics of the board. Btw, you did posted at the wrong session of the forum.

thejoe

Re: Fuzz with 2 lm386 chips?
« Reply #2 on: April 21, 2018, 02:15:51 PM »
Oh shoot. Sorry about that.  Is there a way to move the post? Thanks for the heads up.

The schematic is basically this circuit minus the volume pot, plus the cap between 1 and 8, and going to the next chip instead of a speaker.

My breadboard is kind of messy. Not sure pictures would help. I'll try and dig around.




bluebunny

Re: Fuzz with 2 lm386 chips?
« Reply #3 on: April 22, 2018, 10:19:20 AM »
Did you double-up exactly the circuit you posted?  I think you need to show us exactly what you'd built - schematics and photos.  Pictures work better than words.  :)
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thejoe

Re: Fuzz with 2 lm386 chips?
« Reply #4 on: April 22, 2018, 10:32:34 AM »
Unless I've made mistakes with drawing it up, here is the current schematic.


And a very sloppy breadboard




duck_arse

Re: Fuzz with 2 lm386 chips?
« Reply #5 on: April 22, 2018, 11:02:00 AM »
your circuit dia shows that you need a cap between pin 5 of the second 386 and the 100k pot. what is that pot for, variable power waste? it is wired to burn its track at low resistance.

seek out the tufnell distortion circuit.
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thejoe

Re: Fuzz with 2 lm386 chips?
« Reply #6 on: April 22, 2018, 11:14:07 AM »
At the moment the pot is there just to roll back volume while testing. I know it's not the perfect solution but it was the only PCB mount pot I had lying around so I just threw it in there quickly to keep pop and hiss to a minimum while swapping parts.

Also, the switch in the schematic is not present on the breadboard yet because it was an experiment.

duck_arse

Re: Fuzz with 2 lm386 chips?
« Reply #7 on: April 22, 2018, 11:45:41 AM »
rolling back the volume is fine, but you need to wire it a volume, not as a variable resistor. connect your 386 to the output cap to the "hot lug, CW" of the pot, ground the "cold, CCW" lug, and take the output from the pot wiper. this will then present a [reasonably] stable and [relatively] constant load of 100k to the 386, whatever volume setting you choose, instead of a varying load resistance as in yr dia.
"I'd like to be an angry prophet denouncing the hypocrisies of our time."

"the pub takes care of that for you".

Ben N

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Re: Fuzz with 2 lm386 chips?
« Reply #8 on: October 16, 2018, 03:23:06 PM »
Look for the Frantone Peach Fuzz.