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Mangler and zombie sound gritty

Started by add4, April 07, 2012, 03:10:33 PM

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add4

So i breadboarded a mangler and a zombii today, using the germ trannies i bought.
I find both of them sound very bad: the sound is not smooth and natural sounding. and the decay is too fast for my liking.
i measured both the trannies at about 80 hfe.
I know that the second transistor of both of these effects should be around 130hfe.
Is it possible that my problem comes from that? or am i just not into the germ sound?

jkokura

It could be any number of things, including poor biasing. In many cases, you'll want to include a method to adjust the bias voltage, as bad bias voltages will sound the way you're describing.

Could also be that you need that second transistor to be a higher HFE, and it could also be the germ sound, but I doubt that. What kind of transistors are you using and where did you get them? If the leakage is bad they won't sound good either.

Jacob
JMK Pedals - Custom Pedal Creations
JMK PCBs *New Website*
pedal company - youtube - facebook - Used Pedals

add4

Hey Jacob, thanks for your help!

Transistors are russians 1T308V reported to be low leakage and +- 80hfe and das musikding AC128 (HFE 80-90).
I tested the russians with my multimeter trannies tester and read about 88, which, if they indeed are low leakage, is more or less what i hoped to read.
I plan to build a small board for testing them for leakage and real hfe, but haven't don't it so far.

It indeed sounds exactly like a badly biased transitor, but what i don't get is that i had exactly 4.5V on the bias for the mangler, and that if the zombii needed biasing, i guess there would be a trimpot into it, right?


jkokura

Bias isn't as important with the Zombie, but that's because it's calculated to give you that 4.5 there, and since there are some crazy things going on with the xtra controls it's not as necessary.

But 4.5V doesn't necessarily automatically mean biased. It could be that you need to bias that mangler by ear. Especially becase the expected HFE on the second transistor is higher than you've got in there. I'm not a Fuzz expert though, maybe Paul will be able to offer you more.

Jacob
JMK Pedals - Custom Pedal Creations
JMK PCBs *New Website*
pedal company - youtube - facebook - Used Pedals