# Carcass Fuzz transistors choice



## eh là bas ma (Mar 11, 2022)

Hello,

I have been trying various transistor combinations in the Carcass circuit, without real progress...
I am looking for a more precise and smoother overdrive/distorsion sound (too much splattery and fuzzy for me, as it is), and a fuzz able to mix harmoniously with it.

I have on hands :

2N5089 Hfe= 400-1200
2N5088 = 300-900
2N5087 = 250-800
MPSA13 reading 900 Hfe
MPSA18 = 400-1500
2N2369 = 60-120

Unfortunatly schematics are unpossible to read when I try to enlarge the picture :

https://docs.pedalpcb.com/project/Carcass-PedalPCB.pdf
I don't know wich transistor does what, for exemple : Which transistors are into play with Before (OD) or After (Fuzz) ?

Would something crescendo make sense ? Like Q1= 5087, Q2= 5088 Q3 = 5089 ?

Every suggestions are welcome !


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## Coda (Mar 11, 2022)

I don’t think changing transistors will get you where you want. The transistors to provide gain, yes; but the tone of the pedal is shaped by the rest of the circuit. If your not looking for fuzz, maybe try a pedal that’s not a fuzz pedal…


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## chongmagic (Mar 11, 2022)

Yes this circuit is known for its nasty high-gain fuzz, definitely not the circuit for you if you are wanting a smoother OD/distortion tone.


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## eh là bas ma (Mar 11, 2022)

Thanks for your replies !

I would like to have both : an interesting distorsion on its own, also able to go in the "nasty fuzz" dimension, when I turn the After control CW. That's impossible with this circuit, you think ?

Edit : this pedal is close in my mind with the Pacifier (DOD Punkifier), even if the circuits are really different. There are an "OD" control and a Fuzz control wich mix perfectly with the OD. A Fuzz/Od blending circuit... Am I wrong to see it that way ?


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## eh là bas ma (Mar 11, 2022)

I noticed this comment on musikding :

"hFE of main transistors was around 700 and the fuzz seemed squalling, I changed them with some others transistors, from BC series, with 550 hFE and now Carcass Fuzz is roaring like a beast"









						Carcass Fuzz kit, 32,00
					

Versatile Fuzz




					www.musikding.de
				




Any idea what did he mean by "main transistors" ? As last resort, I will try BC550C and BC557C when i'll get them, and report... My five 2N5089 are all reading between 460 (1 of them) to 510 Hfe (4), I am not sure I'll notice anything.

I wish I could understand how these 5 transistors are interacting with each other...


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## mdc (Mar 23, 2022)

The first transistor is part of an input buffer.  The subsequent transistors are used in a series of gain stages. Two before the clipping and tone section, two after. 

"Before" is a voltage divider that comes after the input buffer. None of the transistors are really going to have any effect on that—the input buffer stage puts out roughly unity gain. The "after" control is a variable resistor on the emitter of Q3.

Does your pedal sound like demo videos or have you been able to a/b it with a DOD example? The first thing to figure out whether something is askew with the pedal or if you're just not into it.

You could try subbing Q2/3/4/5 with very low gain transistors - maybe an MPSA42 - and see if that works for you? Unless the pedal is actively squealing or oscillating wildly, going from a 700hfe transistor to a 500hfe transistor isn't really going to do very much. Maybe start by switching Q2 and Q4 and keep Q3 and Q5 higher? Might sound cool? Might sound worse? Who is to say!


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