My ASM1 is working! - but still some problems!

Stopp,Gene gene.stopp at
Tue Dec 30 01:37:00 CET 1997

Congratulations on your successful assembly!

>The modules worked from the first time I powered the ASM1 on. I only
>burned a  resistor due to a misconnected tantal-cap.

Burning a resistor is a little step towards spiritual enlightenment. :)

>1. The Oscillators seem to modulate each other even when not connected
>more than the onboard lines. I can hear that when I just listen to one
OSC and
>change the tune of the other. At low frequencies this is very clear.

My suspicion is that you have a higher-than-zero impedance in your power
supply lines. How large is the wire that you are using? The wires coming
from the power supply voltage posts and going to the ASM-1 (and the
panel pots) should be thicker than usual, maybe 18 gauge. Also, you did
install the power bypass capacitors all over the board, right?

>3. The VCA produces a plopp-sound at the start of an Envelope, but only
>when connected to the VCF. Some kind of feedback perhaps?

In this case it sounds like there is a DC offset on the filter
output(s). Did you adjust the offset trimmers on the 3080's? If so, did
you use a scope?

>(I am running my ASM1 by a PAIA MIDI2CV8, it?s supplied by an
>Elektor-Formant-like power supply)

Is the ASM-1 powered by the same supply as the MIDI2CV8?

>That is most I have recognized yet. Apart from this I am quite happy
>with it and optimistic to solve these problems.

Another idea: clean the PCB again. Use lots of high-strength de-fluxer.
I have had several DIY projects behave badly in many strange ways, all
due to solder flux that was not completely cleaned off. The VCO's may
not track, or extend to their widest ranges, the VCF may have high
offsets and lock up at high or low cutoffs, the ADSR's may not attack
and decay properly..... there are so many things that residual flux can
cause it's almost scary. Use a whole can if you have to - it's worth it.

>Happy X-mas, Heiko

Happy X-mas to you to!

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