ASM-1 up and running

Magnus Danielson magda at it.kth.se
Fri Oct 4 09:14:00 CEST 1996


>   Just thought I'd mention, I have my ASM-1 project up and running. I built it
> with the maximum amount of pots and jacks. Almost everything worked
> perfectly right off the bat. It sounds great ! I'm still ironing
> out a few problems here and there.

How nice :)

> One thing I recommend is soldering in the
> "optional" 30pf capacitor across the feedback resistor of the VCA, otherwise
> you will get high freq oscillation on the output of the VCA's, only at a certain
> control voltage input level. This can be heard as "clicking" when you modulate
> the VCA every time you pass that certain voltage. Adding the capacitor gets rid
> of the problem.

Aha...

>    One thing that has me stumped is that the with really low frequencies
> (like less than 1 hz), the output of the LFO seems to be asymetrical. On
> the triangle wave, the rising part takes a lot longer than the falling
> part. On the square wave, the voltage stays low for much longer than it
> stays high. I believe I just used a ceramic dip capacitor, could this be
> the problem ? Apparently it's discharging faster than it's charging at low
> frequencies. Also, although my LFO goes well up into the audio range, it
> stops oscillating when it gets below around .2 hz. Of course I'd like the
> LFO to do really slow sweeps. As far as I know I put the proper components
> in.
>   Anyone have any suggestions ?

Well, I try to avoid the ceramic cap's as much as possible... they leak 
considerable more than certain other type's in the same range. When I go about
building my ASM-1's I will use plastic caps (probaly polypropylen... they are
quite cheap anyhow). There are polypropylen's available at 1uF (not as cheap,
but you use up only one per ASM-1 board....). You can use polycarbonate or
polystyrene as well... mylar (polyester) should also make an improvement...

Hope it helps...

Cheers,
Magnus




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