[sdiy] LFO's showing up on VCO

[Simon Brouwer]

Simon Brouwer schreef:
> I'd look for varying current into the ground. Even though the ground 
> conductor has a small resistance, it is not zero, so current running 
> across it will result in a voltage difference. Thus the ground of the 
> circuit that generates your CV and that of the VCO's may not be at 
> exactly the same potential. Assuming no current in the CV conductor, 
> the potential of the CV will be the same on both sides. So the CV that 
> the VCO sees (referenced to its ground) will include the error voltage.
>
> Does it help if you disconnect R515 and R615? These would inject about 
> 2mA p/p of square LFO output into the ground.
I mean R515 and R565.
>
>
> Dan Snazelle schreef:
>> I am not sure of the technical name for the problem of circuits 
>> (lfo's especially) influencing your Main VCO'/'s, but it's a problem 
>> i have had before. The difference this time is I am working with a 
>> pcb (asm2) that has all of the circuits on ONE board, utilizing a 
>> single PSU but with a +/-10 v reference for the VCO. ( i had hoped 
>> the reference would get rid of this sort of problem)
>>
>> Now that all the circuits are working, i am finding myself pulling 
>> out my hair due to HEARING the other periodic circuits making my VCO 
>> output unstable. (even with the CV's disconnected, i can still hear 
>> them messing with the waveform)
>>
>> at this point i am not willing to add a second power supply to this 
>> board and i dont think it would fit anyway.
>>
>> SO...i am looking for ideas. I tried removing the LEDS attached to 
>> the LFO  but that didnt seem to help. HOWEVER i am wondering if 
>> giving the LEDS their own ground (straight to the PSU) would help.
>>
>>
>>
>>
>>
>> I am using a power one +/- 15 volt supply
>>
>> here is the link to the circuits:
>> http://www.elby-designs.com/asm-2/asm2.htm
>>
>> thanks so much
>>
>>
>>
>>
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>>
>>
>>
>>   
>
>


-- 
Vriendelijke groet, 
Simon Brouwer. 

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