Optical tremolo fizz

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Tommygun011198

Member
Hi all,
I’m plagued by an issue with some optical tremolos which I can’t seem to resolve, where I am hearing a ‘fizz’ in the tremolo when guitar signal is passed through. In some cases the fizz is only present in the peaks, when the volume is at the highest, but in the sound clip I just recorded it seems to be present whenever guitar signal is passed through. I first had the issue with the pedalpcb harmonic tremolo, and since then I’ve built the coda effects montagne tremolo which uses an electro Druid LFO. In my pedalpcb build I used a pair of LEDs and LDRs and in the coda effects build I used a vactrol. Both display the same issue but the pedalpcb fizz is more obvious. Hopefully the video clips make the fizz clear. The fizz gets quieter and eventually disappears the more I turn my guitar down, but that’s not really a solution lol.
Has anyone experienced this issue before, or does anyone have a possible solution? Both effects work as intended, but I refuse to believe this is just an issue that plagues every optical tremolo out there
 
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Pictures of a build? what exactly are you using to power the effect and do you have it isolated from other effects.. have you tried just using the guitar and only that pedal.... Have you tried different guitar cables and patch cables...Are you using a cheap guitar with single coils standing next to a fluorescent light? are you wearing a tin foil hat? etc etc
 
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I am assuming your builds are all true bypass?
You could be overdriving the last stage. Check the pin voltage, ensuring Vref is half of V.

This sounds like harsh crossover distortion to me.
 
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swelchy said:
Pictures of a build? what exactly are you using to power the effect and do you have it isolated from other effects.. have you tried just using the guitar and only that pedal.... Have you tried different guitar cables and patch cables...Are you using a cheap guitar with single coils standing next to a fluorescent light? are you wearing a tin foil hat? etc etc
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sorry only just seen this response lol, i actually plug it directly into the 230V (UK) mains using a fork and screwdriver and i use a special testing guitar which is basically a toaster with pickups mounted to it ;)

i use 9V batteries for testing, the guitar works normally with the amp when the circuit is bypassed etc. the room is fairly noisy but ive isolated the noise to the circuit
 
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Tommygun011198 said:
Thanks for the reply! Yeah all my builds are true bypass, I’ll give this a check thanks for the suggestion!
Click to expand...
The measured vref was 4.3V and the battery reading was 8.8V so I don’t think the opamp is causing the distortion unless the opamps are out of spec..? I’ve tried the circuit with both TL074 and LM324, both have the same issue but LM324 has a slightly lower noise floor.
This is my pedalpcb pendulum tremolo which also has the issue, I know the soldering isn’t that great but the effect works (with the issue)
I also breadboarded the schematic and found the same issue so it must be a component but I can’t quite figure out what.
Hi @Robert do you have any suggestions?
 

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