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I’m having an issue with a strange fluttering noise, I isolated the two sides with the calibration mode and it’s happening on the high side, as it reaches its quietest point of the wave there’s a strange rapid fluttering for half a second. Any ideas?
The only voltage measurement that seems off is the led on the high side, instead of ~1.8 I’m getting ~3v
Just desoldered the jumpers, reset the trimmers, soldered again and made no difference. It’s like half the cycle has this really fast fluttering in the high end, similar to the other thread I’ve bumped with the ring mod like sounds. Clock noise?
Or if clock isn’t the right term, something similar
Tried running off a battery, no improvement
When I tweaked the high trim pot slightly it started making the noise on its own with no input signal – sounded like a cat purring
The rate/intensity of the fluttering can be changed with the multiply control, though it is always faster than the rate of the effect
Clip – https://on.soundcloud.com/ceyEhAyGYkBa9n7e8
The first bit sounds like there’s two speeds overlaid, it is set extremely slow and there’s a medium and extremely fast trem at the same time. Once it gets up to a medium speed the issue goes away
The rate led action seems smooth until the quietest part of the wave when it seems to judder at the same time as the strange noise
I just moved the spacing knob and the rate jumped significantly
To clarify I had it set slow and I turned the spacing knob anticlockwise and the speed suddenly jumped to a very high rate
If I turn the rate below 12 o’clock the issue starts but if I tap that slow it doesn’t
I’m sorry for the delay in responding. I just got back in town.
This is a very strange issue. It almost sounds like the PWM from the microcontroller is making its way through the optocoupler to the signal path. My initial thoughts are to ensure that all the components are installed correctly (proper orientation) and to ensure all the solder joints around Q1, opto1, and the trim pot are solid and not shorted to anything. Also ensure that the solder joints don’t have too much solder on them; sometimes this can cause the joints to act as antennas, broadcasting the signal to other parts of the circuit. Also make sure all the components are installed correctly.
Are you testing this with the sine wave function? You should be for these tests.
You mentioned that you adjusted the high trim pot. Please move it in the opposite direction that caused the purring sound. It could be set too high. Ensure that it is working properly; you should be able to turn the high signal off by adjusting it all the way in one direction (25 turns). Does purring sound go away when you adjust it to where all the high signal is gone, or does the purring stay the same or get louder?-Brach
Ah sorry the purring sound was only when I tweaked the high side but it seemed to match the issue but it was making the noise on its own rather than applying it to the signal. I’ve since desoldered the jumpers and carried out the setup process again.
I’ll check those parts and joints tomorrow and let you know, thanks!
Those parts/joints look ok.
The issue only starts when the rate knob is lower than 12 o’clock. The rates below 12 o’clock are very slow and barely perceptible as a trem effect, kind of ‘kicks in’ at 12
