tap tempo tremolo ticking noise

[luciano]

Hello everyone, using the tap of chips Ifo electrodruid I made a tremolo, everything works, the only problem is unbearable lfo noise. I tried various RC filters, LC filter but have not solved the problem. can someone help me ?

[luciano]

http://it.tinypic.com/r/wl7q1d/9

[idiot savant]

You should beef up your power supply filtering a bit. Your analog Vref(the junction of the two 100K resistors) should be stabilized with a decent electrolytic cap. You should also have another electrolytic at the output of your 5V regulator.

Aside from that, keeping your analog and digital grounds separate, and connecting them at only one spot back at the power supply is a good idea.

[luciano]

You should beef up your power supply filtering a bit. Your analog Vref(the junction of the two 100K resistors) should be stabilized with a decent electrolytic cap. You should also have another electrolytic at the output of your 5V regulator.

Aside from that, keeping your analog and digital grounds separate, and connecting them at only one spot back at the power supply is a good idea.

Add two caps, one to vref of 100uf and one outlet of the regulator always 100uf, I separate the ground, the groud of the opamp with the audio ground and the ground of the LFO, then both connected directly to the dc connector. the separation of the ground is done so well?

[luciano]

I added the 470uf cap, but nothing has changed, perhaps slightly


http://it.tinypic.com/r/mmbjtx/9

[Firesledge]

What is an "unbearable lfo noise"? Could you record it?

[Benoi31]

Hello, try to remove R11 and R30. It helped me a lot, even if I still have a small bit of noise with squared waves.

The problem is also PCB organization. you need to connect digital and analogue ground in one point only (with a big a** electrolytic capacitor there if possible).
I had many problems with removing the ticking noise of the LFO, it is quite a hard job to do...

Good luck !

[luciano]

I tried to remove R30 and R11 but then there is a problem in tl78l05, the output is not 5v but 8v, but with the resistor is 5.2V, I exceed the dropout without resistor . but the problem remains, I connected the ground audio directly to the DC jack, with a cap before then from 470uF to 1000uF having always the same result. the cap is put on the dc jack between negative and positive, is that right?


audio file :

https://www.dropbox.com/s/c1g9tvrexkssb91/Lfo%201.m4a?dl=0.  ( 470uf cap)
https://www.dropbox.com/s/9di235dk7sekzxy/1000uf.m4a?dl=0.    (1000uf cap)

[ElectricDruid]

Hi Luciano,

There's a massive thread on here about the tap tempo tremolo:

http://www.diystompboxes.com/smfforum/index.php?topic=84020.0

If you use the search function, you ought to be able to find what other people have done to solve the occasional ticking problems. IIRC, sometimes it depends on the opto, but reducing the current through the opto and the LED can help too. I'm sure there are further ideas in the thread.

Good luck!

HTH,
Tom

[luciano]

Hi guys, I just hear it now because I wanted to do a lot of tests. I followed all the tremolo tread pages, but the ticking did not go away. I redone the circuit twice, even on breadboard but the tick remains. I tried various opto, VTL - nls - led + photores. I no longer know what to invent.

Hi Luciano,

There's a massive thread on here about the tap tempo tremolo:

http://www.diystompboxes.com/smfforum/index.php?topic=84020.0

If you use the search function, you ought to be able to find what other people have done to solve the occasional ticking problems. IIRC, sometimes it depends on the opto, but reducing the current through the opto and the LED can help too. I'm sure there are further ideas in the thread.

Good luck!

HTH,
Tom

[fozzy]

I am having the same type of issue with a different pedal, but I traced the two sounds (ticking & high pitch) from pin 5(pwma) & 6(pwmb) of attiny84, any thoughts?  I have tried many things, rebuilt multiple times, another chip, fuse bits etc.

[idiot savant]

If your grounding arrangement is sub-optimal, it can be a real bear to get rid of noise and ticking. Aside from redoing your layout, and using more power supply filtering, here's something else you can try:

Try running your optocoupler directly from the pwm pin, without the transistor there. So, pwm pin-->resistor-->photocell led. Its not a great way to do it, but if grounding is poor, it may remove one extra path that the high speed pwm can leak into ground. The processor should be able to drive the led directly if you keep the current through it reasonable. You could also try using a different transistor or a mosfet to drive the led.

Another idea would be to try driving the LED in the opposite way shown in the schematic. This would be pwm pin-->resistor-->LED(anode), then from the LED(cathode)-->ground