Pitch Witch trouble

[MaWi]

Hi everyone,
this is my first post here; I just finished a Pitch Witch, and it works somehow, but not as it should.
Bypass works.
The on/bypass LED works, though I´m not sure it it supposed to blink when on.
The delay part works, although all the delays come with a very ugly buzzing/distorted sound .
The modulation part works, if I use a flashlight on the LDR; the yellow LED blinks, but very very dim, even in a dark room barely noticeable. It also blinks as dim in bypass mode, maybe it is supposed to do so?
I appreciate all your help, be patient, my understanding of all electronic things is sub-basic on a good day

 

[carlinb17]

Hi - Similar problem here.
I bought a kit from Musikding. The modulation works just fine, but the delay signal has a crackling/static sound when connected to the amp. I aslo tried it on a Nux Mighty Air (a mini modelling amp with wireless plug). In this case, the audio defect didn't come as a crackling noise, but rather as a high pitched whine.

If the noise was constant it could be rather cool (a sort of added lofi component), but since it comes with the delayed signal it gets really percussive and really annoyingly in your face.

I've tried it in the metal box and outside of it. Same problem. Tried resoldering all the joints. Same problem. The pots have isolating stickers on the backs.

Wit all knobs set around noon, I get similar voltages as MaWi:
IC1
1: 1.30
2: 0
3: 0
4: 0
5: 4.35
6: 8.70
7: 4.35
8: 1.31

IC2
output: 5.02
input: 8.72
common: 0

IC3
1: 5.01
2: 2.51
3: 0
4: 0
5: 2.78
6: 2.51
7: 0.14 (differs from MaWi's reading; sensitive to knob settings)
8: 0.74 (differs from MaWi's reading; sensitive to knob settings)
9-16: 2.51

IC4
1: oscillating, 3-5ish, i have an old & poor dmm
2: 4.37
3: 4.37
4: 0
5: oscillating, 3-5ish, i have an old & poor dmm
6: 4.35
7: oscillating, 2-7ish, i have an old & poor dmm
8: 8.71

Finally, a pic of the "upside" of the PCB mounted in the box.
View attachment 16813
Any help is appreciated!

I’ve had similar issues with circuits that involves an led displaying a rate or some other aspect of the signal. For me it came down to I was using an led that had a high forward voltage. I suspect it could be the same with yours the ultra bright led could be drawing more from the circuit than was intended. The led is associated with the depth pot in this circuit. If it worked better with a brighter led could you add one with a lower forward voltage and change the ldr to one that is more sensitive. I’m sure someone else has ideas but this has been my experiences.

 

[zwkelly]

Thank you to everyone who submitted comments - directly related or tangentially so. I was getting a little noise when playing - like the verge of digital distortion/8-bit. I had used an LM386 (M-93) - a part from an IC kit off Amazon. I switched that out for the LM386N-4 (Smallbear; for Ruby Amp) and that distortion is gone and the pedal sounds great. Second - if you are having trouble with the status LED, keep in mind that there can be no extra resistance... I have prewired resistors with 4.7K pre-installed. Well, that extra resistance was causing the LED to barely blink at the most extreme settings. Switched it out for one without extra resistance and voilà! FWIW if it were to help.

Let me add that the status LED is very useful in getting a sense of what you are doing with the various mod knobs - it's hard to explain - you don't necessarily hear it the same way if you don't see the LED blinking/you seem to miss things that are more obvious when the light providing a visual reference.

 

[BrainDrain]

I built one of these last week and it sounds great. This is what I used:

- 5mm yellow diffused LED from Tayda. This particular LED disperses the light really well from the top and all sides - better than others I’ve tried. Just a nicer full glow. They’re great for these kind of effects.

- GL5528 LDR

- changed the CLRs R14 and R15 from 10k to 1k to let the yellow LED be a bit brighter and for the blinking status LED to also be brighter and pulse stronger. 10k is a bit much for most LEDs.

- soldered the LED flush to the pcb and put the face of the LDR right against the side of it. This is how the original Mid-fi Electronics version was done.