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Egodriver doesn't distort

Started by add4, December 28, 2011, 08:24:15 AM

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add4

So i finished the ego driver earlier, fired it up, and i only work as a clean boost.
All the pots are working, the boost switch does work too, the gain pot only add boost, volume and tone control volume and tone as expected.
Yes i did do the LED mods.
i thought it would come from the signal not entering the clipping section of the circuit, so i reflowed all the parts into it and checked for conductivity with multimeter and audio probe.. i can definitely hear something when i touch the pads of the diodes ... so the signal goes there..

the led never turn on so i guess they don't conduct and don't clip. so i thought maybe my signal is not amplified by the IC and leaking through the feedback loop... i checked the IC voltages, with TL082 i get:

1 4.5
2 4.1
3 2.8 <- problem ?
4: 0
5: 4.5
6: 4.5
7:4.5
8: 9

it all seems corret to me except the third pin
pin 3 connects to the input section which has :
bias resistor to VB -> checked VB i have 4.3 V -> OK
so i guess i have a problem somewhere between VB and pin 3, which is R3 R2 C1 and R1... is is possible that no distortion comes from an input problem?
still hunting.. i'll take any advices until that :)

add4

If someone needs more informations, i'll be happy to provide them.
i checked the input section and it seems right, good values for the parts, continuity is ok on each pad, reflowed all solder joints on the whole board.. still nothing.
any suggestion?

oldhousescott

#2
Pin 3 measurement is OK. The DMM loads the circuit at the point causing a low reading.

Check your clip switch wiring. If it's not connected correctly, you won't get any clipping/distortion.

add4

Thanks for your help.
The switch is wired correctly, i did an audio conductivity check and the switch works correctly: i have continuity and 0 resistance between center lug and each one of the side depending of the switch position.
I also checked continuity between switch pad and diodes legs (the ones wired on the board) and then from the other diode leg to the pad of R3 (diodes are wired to one of the legs of R3). I also checked that this specific pas of R3 is wired to R14 which is the beginning of Vb.
everything seems correct ...
I don't really know what to look for there .. any other suggestion?


Quote from: oldhousescott on December 30, 2011, 04:42:13 AM
Pin 3 measurement is OK. The DMM loads the circuit at the point causing a low reading.

Check your clip switch wiring. If it's not connected correctly, you won't get any clipping/distortion.

add4

problem solved : i subbed C3: 68n for .... 1n instead of 100n.
result: a lot of gain loss -> no distortion.
it works now .. thanks for your help

oldhousescott

Glad you got it sorted! It's a nice sounding pedal and I'm sure you're happy to get it going.

add4

it is a nice sounding pedal indeed. maybe the best dirt pedal i've played so far. it really shines with the LEDs. thinking of subbing the FETs for 1n34a to a really different, more compressed sound. i'm not fan of the mushiness of the FETs anyway.