# Dream fuzz / Op-amp muff low gain



## Zamboni (Dec 22, 2020)

I've built about 15 pedals so far with pretty minimal troubleshooting issues but this Dream Fuzz has me stumped. Audio passes through fine in bypass and when the effect is engaged the pots behave as expected except the gain is much lower than it should be, at highest gain setting it has a little crunch.

I've gone through and checked values on all the components and don't see any issues there. No leads crossed / loose wire strand either, in case the pics don't show that. I swapped both ICs with spares and that didn't help. 
Using an audio probe there's a good amount of gain coming out of the first IC (JRC4558) but then after C6 / R5 the signal is pretty much back to clean, so I'd imagine the issue is related to that but I'm not sure what to try next. 

I checked voltages on both ICs:

IC1 - JRC4558    
Pin 1     4.3
Pin 2     4.3
Pin 3     4.23
Pin 4     0
Pin 5     4.26
Pin 6     4.29
Pin 7     4.29
Pin 8     8.6

IC2 - UA741CP    
Pin 1    0
Pin 2    4.7
Pin 3    4.45
Pin 4    0
Pin 5    0
Pin 6    4.7
Pin 7    8.6
Pin 8    0

Any ideas are much appreciated.


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## Nostradoomus (Dec 22, 2020)

Looks like you have a 4.7r resistor at R9 and R17, should be 47r (yellow,violet,black,gold,brown)


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## Zamboni (Dec 22, 2020)

Nostradoomus said:


> Looks like you have a 4.7r resistor at R9 and R17, should be 47r (yellow,violet,black,gold,brown)


Not sure what’s up with the color codes on those but they measure 47r and match this pack from tayda that also measure 47r:


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## Nostradoomus (Dec 22, 2020)

Ah weird. Well if they measure fine that’s all good! In different lighting I see the gold stripe now.


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## Nostradoomus (Dec 22, 2020)

Well I’d start with the first step we should all take....scrub that board down with a toothbrush and isopropyl alcohol.


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## Zamboni (Dec 23, 2020)

Thanks for the help so far. Gave the board a good scrubbing and got rid of any flux and it’s behaving the same way. One more potential clue, at max vol/gain overall crunchy tone the level is  below unity / bypass signal volume.


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## Nostradoomus (Dec 23, 2020)

Now that’s it’s clean give it a good inspection for cold solder joints, as far as I can see your values and wiring are good so that narrows it down.


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## mikeperez83 (Jan 19, 2021)

i'm having the opposite issue, i get a loud squeal with mine, self oscillating high pitch squeal. turning it on obviously amplifies it, took the thing apart, replaced the 4558 with a fresh one, changed all the electrolytics, checked other points, replaced the diodes, etc etc. works fine for a little bit, had it on the bench , tested it multiple times, sounded amazing! finally put it back on the board and boom(tested it with multiple power supplies), once again it decided it wanted to squeal again. something in the circuit is screwing something up and i'm at my wits end, even contemplated buying an actual op amp muff.


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## Zamboni (Jan 19, 2021)

mikeperez83 said:


> i'm having the opposite issue, i get a loud squeal with mine, self oscillating high pitch squeal. turning it on obviously amplifies it, took the thing apart, replaced the 4558 with a fresh one, changed all the electrolytics, checked other points, replaced the diodes, etc etc. works fine for a little bit, had it on the bench , tested it multiple times, sounded amazing! finally put it back on the board and boom(tested it with multiple power supplies), once again it decided it wanted to squeal again. something in the circuit is screwing something up and i'm at my wits end, even contemplated buying an actual op amp muff.


I’m kind of ready to give up as well, this weekend went over entire path with an audio probe and can’t really tell why the gain lowers after IC1 and red lower anything that looked remotely cold or suspect with no change.


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