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Need help with DIY guitar effect....Hendrix Fuzz Face

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headbuttking2

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I was wondering if somebody could help me with this..

I just built:
broken link removed

And put it on the inside of a guitar (removed 2 of the pickups in a fender strat and put it there)

I checked it over a million times and it is exactly as it is on the schematic, except for the ground from the battery does not go to the input plug but just goes to the ground of the circuit (since it is not hooked up using a plug from the amp or guitar but hooked directly up to a DPDT switch). I also connected a 1 nF ceramic cap from the 22 uF cap to the emitter of Q2 because I saw that in a similiar schematic of this circuit and thought it might help.

When i turn the "level" all the way up and start turning the "fuzz" up...
There is a very very High pitched squeeling and as you keep turning it up it turns into a very very low squeeling (Kind of like a sound effects of a bomb dropping then exploding).
When I pluck any strings i get sound behind the squelching, but it is pretty much just deeper then the clean version and doesnt sound anything like a fuzz.

However, when I turn the "level" slightly down, I am able to turn the fuzz up with very little squelching, but there is no fuzz.

I had a few theories about this but I am not sure what it is...

1. Could it be from the magnetic field giving such bad feedback from the single pickup? (the circuit is about an inch or 2 from it).

2. Unwanted ground loops? I tried seperating everything using electrical tape but it was no use in fixing the problem.

3. The cable to connect the guitar to the amp I am using is horrible and I dont use it because it has bad feedback through it, but I left all of my other cables at school so this is all i had. Could this be a cause for such bad feedback?

Everything is very well seperated on the circuit board, and I changed everything to ceramic caps except the 100 uF and 22 uF are horizontal electrolytic.

Please any suggestions would help out alot.
 
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The circuit has a lot of amplification. Isn't it causing acoustical feedback when you turn the "level" all the way up? I think the output from the speaker is causing the guitar strings to vibrate, then it is amplified over and over.
Turn down the level and/or move the speaker away from the guitar. Then when you turn up the fuzz you'll hear it unless the level is still turned up so high that your amplifier is clipping all the time.
 
Did you connect the wires on the transistors correctly?
 

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Errr right by the battery, the 9V battery there is a 6V electrolytic. That electrolytic is going to break over


Equally there is a electrolytic (well I really should be calling it a polarised cap) being used as a DC-blocking cap, that is going to break over

I have a bad feeling abt this design
 
I sim'd the stupid circuit and it sure makes fuzz. I assumed a pickup impedance of 1k and fed a sine-wave signal of only 2mV into the thing. With a larger input signal then it will make more (!) distortion.

My sim doesn't have an MPSA18 transistor so I used a 2N3904 that doesn't make any difference.
 

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i always tought that fuzz effect is basically high gain circuit or schmidt trigger causing signal distortion that is nearly square wave (lots of harmonics).
 
A pure square wave doesn't have any even-harmonics distortion, just lots of odd harmonics.. This one is sort of rectified then squared so contains both even harmonics and odd ones and lots of them.

The gain of this circuit is so high that "sustain' would go on for a long time, requiring the player to stop a string from vibrating before playing another string.
 
audioguru said:
The gain of this circuit is so high that "sustain' would go on for a long time, requiring the player to stop a string from vibrating before playing another string.

That is generally a requirement for the style of playing when using these devices - you can get more expensive ones which use an envelope shaper to make the output envelope the same as the input one - but these are far more uncommon.
 
headbuttking2 said:
Thanks for all the replies, but any idea on the squelching?

It's essentially a high gain non-inverting amplifier, so layout could be crucial, poor layout design could easily make it oscillate (feedback from output to input).

Obviously a scope would be useful to check this, but even voltage readings might be helpful - to confirm correct connection and operation.

If you're using a lead that was crap before, then it will still be crap now, is it perhaps an un-screened lead? (a speaker lead, NOT an instrument lead).
 
Could be my amp and the chord..

I am at school right now so I am going to pick up some cables and bring them home..

This guitar effect is a real one and not made by some hack..
The retail is around $90 for this effect so I decided to build my own for like 5 bucks..

Just wondering why the hell this thing wont work.
 
headbuttking2 said:
This guitar effect is a real one and not made by some hack..
The retail is around $90 for this effect so I decided to build my own for like 5 bucks..

Just wondering why the hell this thing wont work.

Did you copy the PCB layout?.

And $90 for that simple circuit is a complete ripoff!. Try looking at the Behringer range of pedals for decent prices!.
 
headbuttking2 said:
Thanks for all the replies, but any idea on the squelching?
Before it was squealing, like feedback. Now it is squelching, like cutting in and out?

You didn't say if the pins on the transistors are wired correctly like my pic.
Check its "fuzz" pot's wiring, it must be correct for it to work:
 

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Yes everything is connected correctly.

I was using Squelching and Squeeling as the same thing.

I used a different amp and cable and it still happens but no where near as bad as it was...

But I am still unable to get much fuzz out of it.
 
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