SOLVED AION Fx Oceanid Cornish OC-1 crackling issues

[harmaes]

I’m creating a new thread to troubleshoot the issues I have with this build:

I’ve just finished building the AION Fx Oceanid today and although its working reasonably well I do notice that it does have noise in the form of crackles. Single coils with the guitar volume on max don’t exhibit this issue but humbucker pickups with the guitar on max volume do have this issue. Reducing the volume to around 8 removes the crackles. Inside trim and playing around with the blend and comp settings don’t influence the crackles. The crackling issues is prominent with guitar and bass BTW. Same issue.

1. Could this be impedance or input related because reducing the volume changes the crackling issues.
2. Could this be related to the LM358N or P opamp as its known for distortion issues?
3. Original uses BC549c, maybe try that instead of the 2n5088? Although I’ve never had issues with the 2n5088.

Overall it’s an OK working compressor but I’ve played better ones that have more control over attack and release like the Origin effects Cali76. The inside trimmer is not doing much to the overall behavior and I find the blend to influence the compression in a peculiar way. The compression feels more like volume reduction with an attack that is too quick IMO and from no compression it kicks in too quickly when turning the comp knob.

Btw, this version of the PCB is different then the builds I’ve seen mentioned here before. The NSL-32 has been installed with the dot (-) top right. The other side of the PCB has the + noted bottom left. Not sure if it would work at all when wired reversely.

 

[harmaes]

I have to mention that I had to replace one of the tiny 4,7uf elco caps with a larger 63v one because I broke a leg of one of them.
It's the right one beneath the middle TL072 opamp. The one right from the 1n5817 and left from the 2 pico caps above the middle opamp are the smaller ones. I wouldn't expect that to be of such influence?

 

[giovanni]

The volume knob is directly affecting the gain of that last op amp stage so if you hear crackling, I suspect it means that it’s clipping. Have you double checked all component values? Using an incorrect resistor or capacitor could definitely cause clipping. Can you share an audio clip?

 

[harmaes]

I did another trial with my tele which has a neck+bridge series switch.
On the single coils and combined pickups there is zero crackle. When activating the neck+bridge series the crackling becomes present.
With crackling I mean a sound like digital clipping. If I set the volume too high on the OC-1 I also get clipping on my audio card. BTW, I'm using a Neural DSP Plini plugin set to real clean without a compressor on.
With my strat there's zero crackle with a P90 neck pickup equipped guitar there's crackle.

- It almost seems related to the pickup output?
- The crackling happens with all pots set to zero. It's not an overload of my audio card (RME Babyface Pro FS)
- The compressor kicks in very quickly when dialed in. At a quarter in I already think it's squishing.

Link to the documentation: https://aionfx.com/app/files/docs/oceanid_documentation.pdf

 

[harmaes]

The volume knob is directly affecting the gain of that last op amp stage so if you hear crackling, I suspect it means that it’s clipping. Have you double checked all component values? Using an incorrect resistor or capacitor could definitely cause clipping. Can you share an audio clip?

With the volume (and all knobs) to zero it's also clipping. I double checked all resistors and caps. Don't see any issues.

 

[giovanni]

I see so it’s the input stage that’s clipping with higher output pickups. I doubt that the pedal was designed to work like that, there has to be something wrong. Can you use an audio probe to figure out which stage is clipping?

 

[harmaes]

I see so it’s the input stage that’s clipping with higher output pickups. I doubt that the pedal was designed to work like that, there has to be something wrong. Can you use an audio probe to figure out which stage is clipping?

I’ll give that a try later.

 

[harmaes]

Ok, I solved the problem by using an audio probe and checking the signal after the first TL072 opamp. After that the signal started crackling where probing before it was a clean signal.
The TL072 opamps I received were TL072IN and I replaced them with TL072P from my own stock and the crackling is gone. No issues with low to higher output pickups now!

 

[giovanni]

Ok, I solved the problem by using an audio probe and checking the signal after the first TL072 opamp. After that the signal started crackling where probing before it was a clean signal.
The TL072 opamps I received were TL072IN and I replaced them with TL072P from my own stock and the crackling is gone. No issues with low to higher output pickups now!

Great! Happy this was such an easy fix!