Aion Oceanid (Cornish OC-1) Volume Problem

[mrtzly74]

Hello,

unfortunately i have a problem with my aion oceanid build. I built the pedal exactly as described in the documentation except for two capacitors C7 + C18. I substituted these with “Styroflex” capacitors of the same value. (This shouldn`t make any difference?).
The pedal works as it should except for there is amplification with all knobs on zero (so the signal is louder when the pedal is turned on). As far as I can tell all the other functions are working therefore there is an increase of compression, volume and “blend” when turning the knobs up.
Also it doesn`t make a difference if i switch the pedal to true bypass instead of buffered bypass (with that mini slider switch).

Name of the project: Oceanid Optical Compressor by Aion Effects (Cornish OC-1 clone)
https://aionfx.com/app/files/docs/ocean ... tation.pdf

Attached is a pic of the pcb.

I contacted Kevin from Aion FX earlier and he suggested to post in this forum. That’s what he said concerning the problem:
“But, it's not something I've heard before so unfortunately I don't have any suggestions, other than that it's probably outside of the envelope detector section and in the main signal path.”

Here are some voltages i measured across the pcb.

Out of circuit battery voltage: 9.62 V

Voltage at the circuit board end of the red battery lead = 9.46 V

Voltage at the circuit board end of the black battery lead = 0.00 V

Q1 (2N5088)
C = 9.12 V
B = 5.15 V
E = 4.73 V

Q2 (2N5088)
C= 7.41 V
B= 0.62 V
E= 0.07 V

IC1 (TL072)
P1 = 4.57 V
P2 = 4.57 V
P3 = 4.15 V
P4 = 0.00 V
P5 = 4.14 V
P6 = 4.56 V
P7 = 4.57 V
P8 = 8.30 V

IC2 (TL072)
P1 = 4.55 V
P2 = 4.55 V
P3 = 4.54 V
P4 = 0.00 V
P5 = 4.13 V
P6 = 4.54 V
P7 = 4.54 V
P8 = 8.26 V

IC3 (LM358N)
P1 = 0.00 V
P2 = 0.02 V
P3 = 0.02 V
P4 = 0.00 V
P5 = 0.00 V
P6 = 0.02 V
P7 = 0.00 V
P8 = 8.81 V

IC4 (LM358N)
P1 = 0.03 V
P2 = 0.03 V
P3 = 0.03 V
P4 = 0.00 V
P5 = 0.07 V
P6 = 0.07 V
P7 = 0.61 V
P8 = 8.80 V

D1 (1N5817 Schottky diode, DO-41)
A (anode, the non-band end) = 9.31 V
K (cathode, the banded end) = 9.04 V

D2 1N914 Fast-switching diode, DO-35
A (anode, the non-band end) = 0.00 V
K (cathode, the banded end) = 0.02 V

D3 1N914 Fast-switching diode, DO-35
A = 0.00 V
K = 0.03 V

Z1 (LM4040-5.0)
1 = 0.00 V
2 = 4.99 V
3 = 0.00 V

[bajaman]

all those voltages look ok to my eyes, so maybe a faulty resistor value - i would check R11 and R12 around IC1a - this seems the most likely place to start looking for increased gain
good luck
bajaman

[mrtzly74]

hello bajaman thank you for chiming in! I checked those resistors and all the resistors around the volume pot but they all seem fine. The volume pot has a value of 96,3 kOhms (measured whilst in the circuit). May this affect the gain in any unwanted way? What in the circuit could cause an amplification? Unfortunately i don't understand too much of the circuit..

[mauman]

all those voltages look ok to my eyes, so maybe a faulty resistor value - i would check R11 and R12 around IC1a - this seems the most likely place to start looking for increased gain
good luck
bajaman

I think bajaman meant: could you please verify that R11 and R12 are both 10k? The color code for both should be brown-black-black-red-brown (10k), I can see R12 which appears to match that, but I can't see R11. (Or maybe you did check, and that's what you meant by saying they're fine?)

[mrtzly74]

thanks mauman for the clarification! But yes i checked the color code of the resistors and they are fine..

[sgtrutters]

Did you ever come up with a solution for this one? I built one of these a couple of months ago and I'm experiencing the same thing. Strange thing is I've never had it happen before, but I finished this OC-1 compressor and Klon clone about the same time and they both are doing it. I have another issue with my Klon as well, so it could be related, but who knows. I'll check my voltages against yours.

Edit, I re-read your post and answered my last question of bypass mode...

[stolen]

Oh god what a terrible circuit. The blend is affected by the volume setting, and does near nothing with volume all the way back. This thing is not made for low comp values at all.

Take out R11 and change R24 to 1k, that should fix it.

Circuit is still bad tho. To properly fix it ditch that atrocious blend implementation and just do a primitive one instead. Then you have the option to rewire the volume pot to go all the way to zero.

[sgtrutters]

Interesting. I'll dig into and see what happens!

I'm one of those that sometimes has a compressor on my board because 'you're supposed to.'

Does it work? Sure I guess.