Running the Abyss at 9v I get some distortion when I dig in, play with hotter pickups, or with my bass. If I strum lightly/normal it’s fine for most of my gear. On a whim I plugged it into 18v (my caps are all of the appropriate voltage) and everything is clear as a bell. I know runnning higher voltage raises the headroom, very nicely in my case, but has anyone else experienced this?
SOLVED Abyss distortion issue
- Thread starter Diynot
- Start date
Ok folks, putting this out there again. After verifying parts, reflowing solder joints, and ensuring no solder bridges, I am still getting distortion with my Abyss build. It looks like I may have a Vref issue on pin 3 of the TL072. At a 9.65v source I am reading 2.15v at pin 3. The other points connected to Vref on the TL074 read
pin 3/4.50
pin 5/4.49
pin 10/4.45
pin 12/4.48
Do these values look correct?
pin 3/4.50
pin 5/4.49
pin 10/4.45
pin 12/4.48
Do these values look correct?
harry_hood
New member
I can’t easily confirm voltage values, but had same distortion with my Abyss when using a hotter humbucker like JB. I didn’t have this issue with lower powered pickups. No biggie, I just run it at 18v to have more input headroom.
Robert
Reverse Engineer
The pull-up resistor on pin 3 of IC is 1M, your DMM is probably loading down the Vref line when taking the measurement.
Thanks for the replies. I ended up switching the 1M to a 10k (not sure the down stream effects of this decision) and that did bring the Vref measurement to around 4.5 like the other Vref points measured. I also changed the TL072 to a TL082 (probably not a huge difference). All said and done I can get a clean signal with the voice knob up to about 11 o’clock. past that it starts clipping, even with single coils. Any other thoughts?
Sturdag Lagernathy
Active member
What's up with the LDR's pushed down like that? Shouldn't they be closer to the led?
Already checked all my resistor values. Typically I stage my resistors with a DMM before placing them on the board. The LDR placement isn’t crucial. It does still vibe. It was a first attempt to try and mitigate the clipping. Turning the voice knob up increases the brightness of the LED and if the LDRs are right on it, seems to make it worse.
Sorry, I meant as the phaser sweeps there is a part that emphasises the bass, is this where the distortion occurs? Or is it throughout?
The bass seems to overload my amp creating distortion in that part of the sweep if I happen to be playing a lowish note, for a long time I thought it was the pedal until I plugged it into my audio interface and discovered it was not distorting.
The bass seems to overload my amp creating distortion in that part of the sweep if I happen to be playing a lowish note, for a long time I thought it was the pedal until I plugged it into my audio interface and discovered it was not distorting.
Chuck D. Bones
Circuit Wizard
Got any spare LDRs? Can you measure their resistance with light shining on them? Depending on the LDR sensitivity, you might end up increasing R26.
Changing R2 to 10K will severely load your pickups if this is the first pedal in the chain. I'd keep R2 at 1M and don't measure that spot. If IC1-1 measures close to Vref, that's good enough.
Changing R2 to 10K will severely load your pickups if this is the first pedal in the chain. I'd keep R2 at 1M and don't measure that spot. If IC1-1 measures close to Vref, that's good enough.
Chuck D. Bones
Circuit Wizard
Those are pretty sensitive. Once you bend them up to face the LED, you won't need very many photons from the LED. If you can't use all of the VOICE control's range, try increasing R26 to 220Ω or more.
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