Zonk Machine voltages and gating

Started by ManicStrat1982, May 15, 2021, 10:15:46 PM

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ManicStrat1982

Ok, so I had this thing sounding good on my breadboard, so I decided to etch this board:

After soldering up the board I realized it isn't sounding like it should. Its like its power starved. If you play hard it sounds pretty ok, but as soon as you quit digging in it sounds terrible. Also, I'm getting an octave up effect on the high strings??
it is a mki transistor set from smallbear, so I know I just need to adjust some resistor values.
This is the layout I used:

These are my voltages:
Max gain:
Q1: e -0.776v  b -0.816v  c -8.34v
Q2: e 0  b -0.1289v  c -4.82v
Q3: e 0  b -0.0139v  c -8.23v

Min gain:
Q1: e -0.776v  b -0.816v  c -8.37v
Q2: e 0  b -0.0418v  c -8.23v
Q3: e 0  b -0.0146v  c -8.27v

I just need to know which resistors to adjust to get a less gated sound, and if said resistors need increased or decreased. Any help would be much appreciated!

Thanks!

iainpunk

seems like the transistors are not leaky enough.
might want to make the Emitter resistor on Q1 bigger, and the collector resistor on Q2 and Q3

cheers
friendly reminder: all holes are positive and have negative weight, despite not being there.

cheers

ManicStrat1982

Quote from: iainpunk on May 16, 2021, 08:16:23 AM
seems like the transistors are not leaky enough.
might want to make the Emitter resistor on Q1 bigger, and the collector resistor on Q2 and Q3

cheers

Thanks, I'll start there and give that a try. 
P.s. i thought that about the transistor leakage, but after checking, all the transistors had around 200ua of leakage.

Big Monk

Quote from: iainpunk on May 16, 2021, 08:16:23 AM
seems like the transistors are not leaky enough.
might want to make the Emitter resistor on Q1 bigger, and the collector resistor on Q2 and Q3

cheers

I think it's the opposite. They have plenty of leakage, hence the excessive gating.
"Beneath the bebop moon, I'm howling like a loon

Big Monk

Quote from: ManicStrat1982 on May 15, 2021, 10:15:46 PM
Ok, so I had this thing sounding good on my breadboard, so I decided to etch this board:

After soldering up the board I realized it isn't sounding like it should. Its like its power starved. If you play hard it sounds pretty ok, but as soon as you quit digging in it sounds terrible. Also, I'm getting an octave up effect on the high strings??
it is a mki transistor set from smallbear, so I know I just need to adjust some resistor values.
This is the layout I used:

These are my voltages:
Max gain:
Q1: e -0.776v  b -0.816v  c -8.34v
Q2: e 0  b -0.1289v  c -4.82v
Q3: e 0  b -0.0139v  c -8.23v

Min gain:
Q1: e -0.776v  b -0.816v  c -8.37v
Q2: e 0  b -0.0418v  c -8.23v
Q3: e 0  b -0.0146v  c -8.27v

I just need to know which resistors to adjust to get a less gated sound, and if said resistors need increased or decreased. Any help would be much appreciated!

Thanks!

Something is off there. I'm not as well versed in the Tonebender Mk. I/Zonk Machine circuit, but I don't you should not be reading voltage that high on the collector of Q2.
"Beneath the bebop moon, I'm howling like a loon

iainpunk

Quote from: Big Monk on May 19, 2021, 10:49:26 AM
Quote from: iainpunk on May 16, 2021, 08:16:23 AM
seems like the transistors are not leaky enough.
might want to make the Emitter resistor on Q1 bigger, and the collector resistor on Q2 and Q3

cheers

I think it's the opposite. They have plenty of leakage, hence the excessive gating.
excessive leakage would give voltages near -1v or closer to ground, not close to the rail voltage, as stated above. this concludes that the leakage is not enough, to bias right.

cheers
friendly reminder: all holes are positive and have negative weight, despite not being there.

cheers

Big Monk

Quote from: iainpunk on May 19, 2021, 02:38:37 PM
Quote from: Big Monk on May 19, 2021, 10:49:26 AM
Quote from: iainpunk on May 16, 2021, 08:16:23 AM
seems like the transistors are not leaky enough.
might want to make the Emitter resistor on Q1 bigger, and the collector resistor on Q2 and Q3

cheers

I think it's the opposite. They have plenty of leakage, hence the excessive gating.

Correct. That's my fault for not reading the post correctly.

Case in point would be in a Tonebender MKII where leakage is too high in Q2. This will drive the Q2c voltage lower and raise the Q3c voltage, often times increasing the voltage on Q3c into the gating region.

Thanks for the correction.
excessive leakage would give voltages near -1v or closer to ground, not close to the rail voltage, as stated above. this concludes that the leakage is not enough, to bias right.

cheers
"Beneath the bebop moon, I'm howling like a loon