386 Fuzz

[blooze_man]

Here's something I threw together on the breadboard. To sound totally cliche, it goes from a good overdrive to heavy fuzz. I had nothing particular in mind for inspiration when I made it, so I might unknowingly be ripping off another circuit. Just thought I'd share.



Edit: I used the 386 N-3.

[FiveseveN]

Here's something that's been lurking in the back of my head for a while: isn't clamping the output with clipping diodes bad for the 386? Should one use a 10ohm resistor between them?
Also, blooze_man, the output is biased at V+/2 so there should be a coupling cap between pin 5 and the diodes. Also you also labeled the V+ pin as 5, it should be pin 6.

[davidallancole]

Generally there would be a cap and resistor in series from the output of the chip to the diodes.  The resistor would limit the current and the cap for the dc voltage.

[blooze_man]

Here's something that's been lurking in the back of my head for a while: isn't clamping the output with clipping diodes bad for the 386? Should one use a 10ohm resistor between them?
Also, blooze_man, the output is biased at V+/2 so there should be a coupling cap between pin 5 and the diodes. Also you also labeled the V+ pin as 5, it should be pin 6.

Thanks for the heads up on the pin numbers. I'll fix it. Is it really necessary to have the cap and resistor? The circiut sounds fine as it is but if there's the potential for damaging the chip it would be an easy fix.

[deadastronaut]

Here's something that's been lurking in the back of my head for a while: isn't clamping the output with clipping diodes bad for the 386? Should one use a 10ohm resistor between them?
Also, blooze_man, the output is biased at V+/2 so there should be a coupling cap between pin 5 and the diodes. Also you also labeled the V+ pin as 5, it should be pin 6.

Thanks for the heads up on the pin numbers. I'll fix it. Is it really necessary to have the cap and resistor? The circiut sounds fine as it is but if there's the potential for damaging the chip it would be an easy fix.

hi adrien, ive never damaged a 386...and ive abused a few of em..its surprising how much stick they can take..

does it fizz on the dying note?....if so try a 100uf across +/-..

have you tried a pot instead of the 10k too...might be interesting..

and last of all, any soundclips?....  rob.
any soundclips of this...

[Electron Tornado]

Take a look at the 386 data sheet. You need a cap somewhere between pin 5 and the output. Most of the circuits also show a cap between pins 1 and 8 if they are going to be connected. Have you tried the circuit without the diodes? Get the chip to clip hard enough and you might decide you don't need them.

Also curious whether you get a buzz or fizz right at the end as notes die off.

[deadastronaut]

also try a 10uf across pins 1-8...hi gain...just a thought!...

[Gurner]

With a 9V supply, there is 4.5V DC sitting on pin 5, which is essentially being shorted to ground through one of those forward biased diodes - fugly.

[blooze_man]

Here's an updated shem. Turns out the diodes were not needed at all. I added a 100uf cap on the power which cut down on noise and, as far as I can tell, it doesn't "fizz." I plan on boxing it up sometime soon and I will try to record some clips.

[Gurner]

Much easier on the eye!

Just one thing...if there is a guitar going directly into that circuit, IMHO the input impedance is way too low.

[twabelljr]

There is also the cap and resistor in series between pins 5 and 1 you can make switchable for a bass boost. (see datasheet). I did it on a Ruby Amp and it gave 2 nice, different sounds.

[CoolJohnny]

as if i needed another 386-based circuit to try this weekend...going to be messing with smash drive/grace ideas and permutations. this looks interesting indeed...i'll have to get it together and see...crap, im going to need more beer!

[anchovie]

Much easier on the eye!

Just one thing...if there is a guitar going directly into that circuit, IMHO the input impedance is way too low.

Too low for what? If it sounds good, maybe it's helped by the treble being suppressed right at the start!

[caress]

Much easier on the eye!

Just one thing...if there is a guitar going directly into that circuit, IMHO the input impedance is way too low.

Too low for what? If it sounds good, maybe it's helped by the treble being suppressed right at the start!

i've been thinking a lot about this lately and it seems like low input impedance might not always be a bad thing... 
takes less parts than adding an additional RC filter  lol

[jcgss77]

+1 blooze!

This is how sweet circuits are born-someone is inspired and boards something, then puts it up, and then a new stompbox is born!  Since you said it had a fuzz sound, maybe put a 555 timer in front, fed 1v, and see what that does with this circuit?  Does anyone think this will work?

[ACS]

Much easier on the eye!

Just one thing...if there is a guitar going directly into that circuit, IMHO the input impedance is way too low.

Too low for what? If it sounds good, maybe it's helped by the treble being suppressed right at the start!

i've been thinking a lot about this lately and it seems like low input impedance might not always be a bad thing... 
takes less parts than adding an additional RC filter  lol

I agree with this to a point.  If it's first in the chain, and it sounds good with a low input impedance, then all good - the pickups are being loaded in a way that produces a 'good' sound which is a good thing.  BUT, what happens if this pedal is after something with a buffer, like say, any Boss pedal out there?  Suddenly, the low input impedance doesn't impart the same reaction 'up the chain' so to speak - and lo! your great sound that you had is gone...

If you can guarantee standard placement and usage, then you're right: input impedance doesn't matter, and if it sounds great, it is great.  But you just need to be aware that a 'non-standard' input impedance may cause unexpected results in other situations...

[Gurner]

I am all for saving components....but once those highs are gone at the beginning of your signal chain - theyre gone.

Far better to keep them in there in the first place & then have the option of removing them - if preferred - somewhere further along your signal chain.

[Renegadrian]

The input stage is very close to a LPB

check the layout I made in a hurry!

[blooze_man]

The input stage is very close to a LPB

Yes it is. I couldn't remember the part values so I threw in what I thought was close.