[sdiy] help with clicks on VCA

[Dan Snazelle]

thanks for the advice

sadly i have tried with three different "lfo" sources (keep in mind, my audio is real audio, not a synthwave....i dont think it would be as noticable on a stright saw or square wave input)

the lfo;s i have tried

1. a 40106 lfo (it is the worst)

2. my serge neg slew run as an lfo

3. and 3, my ken stone lfo

all three make the clicks in their own way!

i am going to try your idea of filtering the high end of the wave,,,it makes sense.





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----------------------------------------
> CC: synth-diy at dropmix.xs4all.nl
> From: tom at electricdruid.net
> Subject: Re: [sdiy] help with clicks on VCA
> Date: Mon, 17 Aug 2009 13:40:42 +0100
> To: subjectivity at hotmail.com
>
> Dan,
>
> Thinking formally for a minute, tremolo is amplitude modulation, so
> it'll make sidebands. Any high frequency content in the modulating
> signal is going to show up in the audio. That'll include abrupt
> transitions in any wave. A ramp wave at 1Hz has a 200th harmonic at
> 200Hz. So adding some filtering on the CV input might help - Slewing
> the control waveform is one way.
>
> In practice, though, I doubt that's what's going on. I rather suspect
> that the problem is with the LFO, not the VCA. The fact the problem
> remains with two different VCA designs might also point in this
> direction. Comparators can generate a good 'click' when they switch,
> and this can get coupled through to the power rails. Does the LFO
> include a comparator? Is the Tremolo's power supply well isolated?
> decoupled? Have you tried sending the VCA a control signal from a
> unit with an independent power supply? (so they only share a ground
> and CV line).
>
> I'd stick 100R resistors followed by whacking great capacitors in
> both rails of the VCAs power supply to filter any noise there out. If
> that cures the problem, then you can try some more calculated and
> careful approach.
>
> It is possible to build a quiet tremolo, so don't give up hope.
>
> Regards,
> Tom
>
> On 17 Aug 2009, at 13:11, Dan Snazelle wrote:
>
>>
>> it happens with square waves too
>>
>> even with saws
>>
>> from what i have been reading this is a very common problem with
>> tremolos
>>
>>
>> thanks
>>
>