I'm trying to make a speaker cranker. I have sound and everything seems to be working, the only problem I have is whenever I turn the "more" knob it makes a whoosh-ish sound. I've been searching every forum and article I can find and the best I can guess is something is leaking DC current into the pot(?) I've measured voltage across the pot with a multimeter and it appears to have about 0.3v with minor fluctuation across pins 1 and 3 while turning.
Attached link is the schematic (my schematic doesn't have the values on them, I'll post what I used below). It seems to do it regardless of being on a breadboard, perfboard or pcb. on the breadboard the sound seemed minimal compared to the other two but was still present.
I can provide more info/pictures/measurements if needed. Any help is appreciated, been wracking my brain trying to solve this for weeks.
Resistors:
R1 - 1m
R2 - 330
R3 - 2M2
R4 - 10k
Capacitors:
C1- 100nf
C2 - 100uf
C3 - 68nf
C4 - 100uf
Transistor is 2n3904
C-0.35v
B-0.87v
E-8.89v
Diodes
D1 - 1n4001
D2 D3 and D4 are germanium (1n34a(?))
EQD Speaker Cranker build issue [SOLVED]
-
bmxguitarsbmx
- Cap Cooler
That sound is normal for a circuit built off this schematic.
The solution would be to not run current through your pot. Substitute an equal value resistor instead. Then use C2 to isolate the pot from DC current.
Hope that makes sense.
It is very similar to how old plexi's (for instance) ran their presence control vs how modern amps run their presence control. The tone will be different though as the sweep will change. A reverse log pot may help you, but even then you cannot dial in the lowest setting of the pot.
The solution would be to not run current through your pot. Substitute an equal value resistor instead. Then use C2 to isolate the pot from DC current.
Hope that makes sense.
It is very similar to how old plexi's (for instance) ran their presence control vs how modern amps run their presence control. The tone will be different though as the sweep will change. A reverse log pot may help you, but even then you cannot dial in the lowest setting of the pot.