Caline CP-46 Fuzzy Bear  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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CheapPedalCollector
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Post by CheapPedalCollector »

Traced this out some time ago, it's mostly surface mount, had to wait until I got a capacitor tester to finish the job.

I still don't know the values of C5/C6/C7 but I don't think they are very important and probably 100nF. I didn't feel like yanking out the Electrolytics to measure them.
CalineFuzzyBear.png
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nooneknows
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Post by nooneknows »

A plain FF, doesn't it oscillate at max? BC549 are quite high hfe devices

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Post by Intripped »

what's the purpose of C9?

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Post by nooneknows »

Intripped wrote: 11 Dec 2020, 14:10 what's the purpose of C9?
agree, that way it doesn't work, it's an open circuit

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Post by CheapPedalCollector »

Intripped wrote: 11 Dec 2020, 14:10 what's the purpose of C9?
I'm guessing just to stabilize the voltage drop across R7. Battery sag emulation I guess?

Yes it's just a Fuzz Face clone, and no it doesn't oscillate, it's sounds awful though. I suppose if you like fuzz that gets really compressy when you hit the notes you might like it. It's also advertised as a "germanium fuzz" which is really funny, maybe the very first release of it had some germanium transistors.

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Post by Intripped »

nooneknows wrote: 11 Dec 2020, 16:56 agree, that way it doesn't work, it's an open circuit
It works because there is R7. C9 is just in parallel with it
CheapPedalCollector wrote: 11 Dec 2020, 22:10 I'm guessing just to stabilize the voltage drop across R7. Battery sag emulation I guess?
this is the first time i see a capacitor used in that position, anyway i'm not expert in battery sag emulation circuits

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Post by CheapPedalCollector »

Intripped wrote: 12 Dec 2020, 07:38 this is the first time i see a capacitor used in that position, anyway i'm not expert in battery sag emulation circuits
C6 and C7 are also strange to me, they are right next to each other on the circuit board, I see no reason for them at all.

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Post by deltafred »

CheapPedalCollector wrote: 12 Dec 2020, 16:59 C6 and C7 are also strange to me, they are right next to each other on the circuit board, I see no reason for them at all.
It's common practice when designing low noise smoothing/decoupling circuits.

One will be an electrolytic, good for smoothing out low frequency (ripple) but less so at high frequencies, the other a ceramic to catch any spikes that the electrolytic lets through.
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Post by nooneknows »

Intripped wrote: 12 Dec 2020, 07:38 It works because there is R7. C9 is just in parallel with it
right, my bad, I was sleeping

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Post by CheapPedalCollector »

deltafred wrote: 12 Dec 2020, 23:11 It's common practice when designing low noise smoothing/decoupling circuits.

One will be an electrolytic, good for smoothing out low frequency (ripple) but less so at high frequencies, the other a ceramic to catch any spikes that the electrolytic lets through.
They are both very small capacitance values, I'll have to pull out the electrolytics so I can measure them I guess. There's already lots of filtering for noise, so maybe just layout noise issue.

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Post by deltafred »

They are there to block not only internally generated noise, which on an analogue circuit is probably minimal, but also to suppress any noise on the incoming DC supply. (e.g. switched mode power supplies or digital pedals with inadequate filtering.)
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Post by CheapPedalCollector »

Yes, it's pretty standard stuff C5, as it's in the power supply section and is slightly larger and I think it is 100nf which is standard filtering there. C6/C7 are not, and appear to be in the pF range (they are same size as the 20pf cap) and well away from the power supply cluster. I'll take some screenshots of the guts.

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Post by Ilya-v »

It is a standard silicon fuzz face.

The power supply section has an error in the schematic on the first post, the 220uF is NOT in parallel to the 220 resistor, and the schottky diode is in series.
You can see on the PCB back that all three electrolytic filtering caps negative leads are grounded, it's just another filtering cap.
SS14 MEV is a reverse polarity protection Schottky diode wired in SERIES and drops around 0.2v (measured) with 2mA the fuzz face consumes.
Volume pot is 500kA on mine, aside from the power supply everything else is a stock silicon fuzz face with BC549 transistors.

Personally I don't like the power supply 8.3v voltage drop so I shorted the 220 series resistor, I've also added a 10k bias trimmer on Q2c, I bias around 4.8v.
Good sounding fuzz, cleans up very well with the guitar volume.

.
Fuzzy Bear PCB.jpg
Fuzzy Bear PCB Back.jpg
Fuzzy Bear Power.jpg
Fuzzy Bear Power Supply.jpg

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Post by CheapPedalCollector »

I'll correct the schematic later today, thanks.

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Post by CheapPedalCollector »

Fixed schematic.
CalineFuzzyBear.png

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