# Carcass Fuzz screeching noise.



## chongmagic (Jan 1, 2020)

I finished up the Carcass fuzz and when the thing is dimed it has a screeching noise. If I turn down the highcut knob that helps some. I did use an A10k instead of an A5k because that was as close as I had onhand. This may be part of the issue. Just wanted to see if anyone else had a similar issue? Possibly too the voltages at the 5089s for comparison.


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## moonlightpedalbuilds (Jan 1, 2020)

After knob at max makes mine screech but stil playable. I also noticed 5089s from mouser sound spikey than 5089s from tayda. I prefer the tayda 5089s. Sounds smoother. 

I’ll check and post the voltages later


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## chongmagic (Jan 1, 2020)

pedjok said:


> After knob at max makes mine screech but stil playable. I also noticed 5089s from mouser sound spikey than 5089s from tayda. I prefer the tayda 5089s. Sounds smoother.
> 
> I’ll check and post the voltages later


I used Tayda 5089s as well, yes it is still playable but it really squeals.


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## Tremster (Jan 2, 2020)

I'm glad I found this thread, I will be following it.
My Carcass does that too. I put it in the box of bugs and haven't looked at it since ...


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## Chuck D. Bones (Jan 4, 2020)

They way Q2 and Q4 are biased, this circuit will be very sensitive to HFE.  It doesn't surprise me that different batches of transistors sound different. It also means that transistor voltages will vary from unit-to-unit. 
This circuit has a shit-ton of gain.  Wire routing and grounding will be critical. Unwanted coupling thru the power supply can cause oscillation, so it's important that C6 and C10 are good quality parts.


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## chongmagic (Jan 4, 2020)

I used Wima and Nichicon caps and measured them.before I installed. I will have to double check my wiring to see if any of that is the cause.


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## Chuck D. Bones (Jan 4, 2020)

You might need to find lower gain transistors.  There really should be power supply filtering between the gain stages IMHO.


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## Robert (Jan 4, 2020)

It's been a while since I had an original, so someone else might have better insight, but for what it's worth, the Black Spiral Fuzz (which is derived from the Carcosa) oscillates by design.


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## Chuck D. Bones (Jan 5, 2020)

I just watched to some Carcosa demos by Andy Martin.  No oscillation.  He never cranked BEFORE and AFTER at the same time.  Great sounding fuzz and a huge variety of tones.  Lots of gain and volume available.


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## Nostradoomus (Jan 5, 2020)

Oh man I never saw part II of that demo with him playing electric wizard riffs...even though I already built a hyped fuzz, I think I need that.







But first, here’s my clean tone.


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## Nostradoomus (Jan 5, 2020)

Also there’s a 60 Cycle Hum demo where they dime it at the end...it feeds back for sure but it’s not the oscillation type.


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## evilarsen (Jan 12, 2020)

Hello everyone, i think have the same here. I have replace the ''after'' potentiometer but the noise is alway here. I did a little video with the trouble.


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