ASM-1 problems

Stopp,Gene gene.stopp at telematics.com
Tue May 26 18:11:00 CEST 1998


>
>hi every body.
>

Hi Gur!

>
>i have some  problems with the system:
>

I'll try to help.

>
>1)both VCO's in all freq are having little repiting change in freq(i
think
>it's the freq i dont have a scope)every 2 sec up/dwon,the power suply
>i use is the MOTM-900 which is well regulated ?
>

Is 2 sec up/down the LFO rate? This along with number 2 below sounds to
me like a power supply impedance problem. It is as if the wires coming
from the power supply have some resistance in them, so that the
different circuit sections are able to influence the power rails. The
MOTM power supply should be quite adequate for this application - I
don't think that is the problem.

>
>2)when changing freq on one VCO i hear a little change on
>the other VCO ,i remember ther was some talking about this on the list
>and the result was nothing to do is it right ?
>

The VCO's in the ASM-1 do not influence each other at all in my systems,
so it must be possible to construct it such that things are not
affecting each other.... Do you have thin wire from the power supply to
the ASM-1? Try to use thick wire - 18 gauge, possibly 14 gauge, whatever
you have available to you. Too thick is better than not thick enough.

>
>3)the gain log pot's on the AMP are starting to
>out put sound frome the middle and with some "teec" noise ?
>

Although I'm not sure what "teec" sounds like, I suspect that the VCA
output amps have a high frequency oscillation on them. This can happen
if you use a TL-082 here (which I recommend in the instructions, by the
way). Try adding a 100pf cap across the output op-amp (from output to
(-) input).

>
>4)the AMP making "teec" noise every time the ADSR open it ?
>

Same as question 3 above.

>
>5)what the offset trimers on the VCF are for,i dont get
>Gene explanation ,i playd with them and did not hear
>any result ?
>

These are tricky to adjust without a scope - try to set the wipers of
the trimpots to 0v first, and see if the filter works OK. If so, leave
them alone.

Oh yes - clean the circuit board to remove *any* solder flux. When you
think it's clean, clean it again!

 - Gene




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