My new circuit - "1983 Fuzz" Old School Atari type fuzz

[artifus]

i'm wondering if you should try a resistor between pins 6 & 7? maybe a pot. i think it's nearly in astable mode but i don't know how zero ohms between the two pins affects performance/stability or just output frequency. check out the second half of this siren circuit, the fast astable: http://www.doctronics.co.uk/555.htm#control

you've removed r2 from this equation: http://en.wikipedia.org/wiki/555_timer_IC#Astable

*also*

The operation of RESET in this mode is not well defined, some manufacturers' parts will hold the output state to what it was when RESET is taken low, others will send the output either high or low.

reset is pin 4 - may account for some folk not having much luck. maybe try pulling it high or low. (connect to + or -)

[nobodysweasel]

So I finally got around to breadboarding this according to your most recent sketch (with the 555). The only change I made was to use a 500k pot because I didn't have a 1M on hand.  Here's how it worked. I'd start with the pot turned all the way down with no sound. I'd turn it up just a tiny bit and get a fantastic sound out of it. My wife even got excited about how good it sounded. But after just a few seconds it would start going crazy. These might not be the right terms, but it sounded like it was self oscillating and/or feeding back. It would get really loud and start squeeling.  Turning the pot up any higher would make the whole thing happen much faster and more extreme. I wish I knew more about what I was doing so I could help troubleshoot this.  It really does sound great for the few seconds it actually works.

[nobodysweasel]

Okay, I got it to work!  Finally!  Which I think makes me the first out of these 7 pages of posts to be able to duplicate it. 

In short, I got rid of the pot and the 10nf capacitor and that did the trick.  I also changed the output cap to 47uf for more bass, but that's just a matter of taste.

I'll go through what I figured out, but you'll have to forgive me if my ignorance shows.  I'm still pretty new at this.

I spent some time at the link posted by artifus and played around with the 555 and an LED until I figured out more or less how to work the thing.  I ended up using the example from that link called "minimum component astable," only I removed the resistor and capacitor so the 555 wouldn't generate any signal except what was input into pin 5 (in this case, coming from the 386).  Also, I replaced the resistor/LED output for a capacitor/1/4" jack (of course - we want this to make sound, not light up an LED).  This gave me a working circuit, but it didn't quite match the sound of the clips posted here.  I was getting something less glitchy, more bass, and with just a different character.

From this point, I just did some intermediates between my own circuit and the one posted just a few posts above this to see what would work.  Here's what I came up with:
- Using a decoupling capacitor (i.e. 47uF from V+ to ground) gives a more controlled sound and less glitchiness.  This was a bad thing as far as achieving the sound we're going for, but might be good if you're looking for something less glitchy/more like a standard fuzz.
- Connecting pin 4 to V+ made no noticable change to the circuit.
- Connecting pin 7 to pins 6 and 2 made the biggest change.  This is where the glitching and character came from.
- I tried altering the location of the pot in the original sketch several times and never got anything useful.  As it is in the sketch, I just couldn't get anything out of it at all.
- The 10nf capacitor in the sketch is a mystery to me.  I have no idea why it's there, and whenever I plugged it in the breadboard I'd just get a clicking and no guitar sound.
- I also had some trouble with the output cap.  It seems the 555 puts out such low voltage that you have to just bang on the guitar for as much as a minute to charge the capacitor and get any sound out of it.  Smaller caps get rid of this problem, but also get rid of the bass.  The best sound I got was with a 47uf cap, which gave more bass than the sound sample posted.  In order to get it to work, I charged the cap before installing it by plugging it into V+ and ground and then sticking it in place in the breadboard.  I don't know if this would be an issue for a permanent pedal or not.  This is a new problem to me.  Could be the reason others weren't getting any sound out of it.
- This thing is really loud.  Using a pot for volume is a good idea.

I'm afraid this is about as far as I can go with this circuit.  Hopefully someone else can throw it on the breadboard and make some improvements.  I bet there's somewhere you could put a pot or two that would do good things.  Anyways, I hope this helps someone, and I'd be excited to hear if anyone else can get this working or make improvements to it.

[nobodysweasel]

Sorry for the triple post (!), but here's a drawing of the circuit as I finally got it to work.

[deadastronaut]

cool, now you have it working, as an experiment try  the 10uf across pins 1-8 on the 386, this will boost the gain from 20x to 200x..

might be good, might not, but worth a go..

[nobodysweasel]

Thanks for the tip.  I really had fun learning about the 555 and am looking forward to learning about the 386 as well.  I'll give it a shot.

[Perrow]

cool, now you have it working, as an experiment try  the 10uf across pins 1-8 on the 386, this will boost the gain from 20x to 200x..

might be good, might not, but worth a go..

He's shorted 1 and 8 in his schematic, so it's already boosted.

[Perrow]

Might place a 1k pot there as a variable resistor and see if lowering/varying the boost some would help or not.

[deadastronaut]

^ of course....

try it not shorted then..

[timd]

So I finally got around to breadboarding this according to your most recent sketch (with the 555). The only change I made was to use a 500k pot because I didn't have a 1M on hand.  Here's how it worked. I'd start with the pot turned all the way down with no sound. I'd turn it up just a tiny bit and get a fantastic sound out of it. My wife even got excited about how good it sounded. But after just a few seconds it would start going crazy. These might not be the right terms, but it sounded like it was self oscillating and/or feeding back. It would get really loud and start squeeling.  Turning the pot up any higher would make the whole thing happen much faster and more extreme. I wish I knew more about what I was doing so I could help troubleshoot this.  It really does sound great for the few seconds it actually works.

Whoa....never thought I'd see this thread again! Thanks for reviving it. I think we can get a powerful little circuit out of this mess in some time. With most circuits, you want to use a standard 100K A pot for volume control - this one especially. From memory, I think I used the 1 M pot to get a hybrid of useable tone and a little oscillation at the end of the sweep. For those that know me, I'm a sucker for oscillation. It appears that I'll have to put this on a breadboard and attempt an update. Great suggestions - I always welcome any and all!

[timd]

I was working on the breadboard with 386 and 555, but nothing came close to the original using the 386 and 556 and the 2 500 K pots. Here's the original - I want that sound in a bug free circuit:

I'll keep working on this. Can any new set of eyes see why the 556 is glitching and heating up? The final finshed pedal in the video works fine by itself, but when in a chain of pedals, causes an issue. I'm thinking component sizes could be an issue?

[kodiakklub]

tim-

1. post a THOROUGH schematic for your latest version of the circuit. the one with the 556 and the 2 @ 500K pots
2. have you been using the same 556 chip throughout the long and winding saga that is this thread?
3. for all of us to compare notes and help each other out, we have to be on the same page, working on the same circuit, or at the very least, be very clear as to what has been altered.

[timd]

I haven't started on the new version with the 556 yet. This is all very recent as this thread was revived from cryogenic slumber. I was working on the version with the 555 today, but it didn't give me the sound I wanted. Unfortunately, I have long since torn everything off that breadboard - so looking back with those specific components is impossible. I still have different 556 chips around though. My goal is to get a working circuit on a breadboard, then try out different 556 chips and make sure everything works fine. I've learned a lot in the last few months, so I should be able to figure it out.

[kodiakklub]

and so it`s very clear to everyone, there are 2 different versions of the 556 and 555. there is a LOW POWER CMOS version. maybe vince and petey were using those and that's why they burned theirs up. the one you were using before is the NON CMOS version, the NE556N. ill wait til tim rebuilds the 556 version before i spend any time on this one again.

[timd]

That could be...I knew there was a low power 555, but haven't heard about the low power 556.

[petey twofinger]

my chips never burned up / got hot .

it did not produce any audio .

i have 555 , cmos 555 , 556 , i tried all chips when i had this breadboarded . i tried quite a few different things , i couldnt get anything happenin though .

[Vince_b]

Mine did burned up, but I can't remember which version of the chip it was. I might retry this circuit, but not before someone comes up with a confirmed working version of it.

[kodiakklub]

we're all waiting for you tim! please post a THOROUGH schematic of you latest and greatest version soon and ill be happy to be a guinea pig

[Canucker]

I've got/built enough normal fuzz pedals so all I want to work on is this type of stuff!...but if you guys can't figure out a glitch theres no way I'll be the one to pull it off. 

[nobodysweasel]

The schematic I posted worked fine for me, and sounded a whole lot like the sound clips/video posted.  I used the regular version of the 555 (not cmos).  I'd like to see someone else try to confirm it.  It should be pretty quick to throw on the breadboard (just 2 chips and cap).

I've been meaning to mess with the 556 version, but I don't have a 556 on hand.  I might have to try using 2 555's when I've got some time.