Kay Tremolo - lfo ticking

Started by SprinkleSpraycan, July 30, 2023, 06:05:52 PM

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SprinkleSpraycan

i have this circuit on a breadboard right now. its really great but there is an audible lfo ticking. after poking at it for a week i cant figure out how eliminate it. is there a way?




ElectricDruid

I don't know, but the usual suspects would be a good place to start: Make sure that the ground paths for the LFO and the audio parts of the circuit are *completely* separate, and only meet where the power comes in.

In this case, that means T4, the Speed pot, and the LFO LED should all have a ground that is totally separate from the rest of the circuit.

The +V power is separated already by that 1K2 resistor, but the same principles apply. Ideally, the LFO's +V power input should be a separate wire to keep any current it draws away from the audio side of the circuit. Since this is not an op-amp-based circuit, you don't get the advantage of the power supply rejection ratio (PSRR) that you get with op-amps. That makes this circuit more fussy, although simpler.

I can't see clearly whether the Das Musikding PCB layout does any of this, but if it doesn't, maybe it ticks too!


antonis

In case of Tom's suggestions don't work, try to place the LED between R12 and T4 Collector..
(it will work 180o out of present phase but I presume you don't mind..) :icon_wink:
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

duck_arse

that circuit shows no supply bypass caps whatsoever. at least one might help.
I feel sick.

SprinkleSpraycan

Quote from: duck_arse on July 31, 2023, 11:10:59 AM
that circuit shows no supply bypass caps whatsoever. at least one might help.

I did do that. A 100uf and 100nf. It made the ticking softer. Any improvement is good.

SprinkleSpraycan

Quote from: antonis on July 31, 2023, 05:52:33 AM
In case of Tom's suggestions don't work, try to place the LED between R12 and T4 Collector..
(it will work 180o out of present phase but I presume you don't mind..) :icon_wink:

I'll try all this today. Cool tip about the led.

SprinkleSpraycan