ASM-1 questions

[Magnus Danielson]

> Hi all (again!),
> 
> I have some questions about the ASM-1 board. First of all I want to improve
> the tracking. I now have some 2n.... matched pairs but this doesn't seem to
> work that well. I've already bought a couple of MAT's but I can't find the
> pinouts. I know this has already been posted but could someone please repost
> me the orientation on the board? 

The MAT-02 have a small tag sticking out on one side, this should point in the
same direction as the notch of the silkscreen on the PCB. The legs is then just
placed out as normal. This has become such a normal question that I think I
better make a picture showing the MAT-02 as mounted at my board. Hopefully that
will clear things up for some people.

See my previous note on the 2N4391-2N4393 transistors. The pin layout does not
match those of the silkscreen. Bend the middle leg over... I'd better do a
picture here too...

> Furthermore I want to change the output levels to a lower standard because
> sometimes the filter will distort and as I'm planning to build the boards
> behind the frontplate by Christopher List, which has only one attenuator at
> the filter section (if I recall that right), I want to set the levels a bit
> lower. Can someone tell me whether it's a good idea to build some voltage
> divider? I thought this should be okay (high impedance of filter!)

You can either use a voltage divider or change the input resistor to the summer
of the filter. The input gain for a signal is decided by the resistor and the
feedback resistor as follows:

	      100k
	G = - ----
	       R

Where R = 100k gives a 1:1 relation (disregarding for polarity change that is).

The input resistors will act as if they where hooked to ground. That is a fair
assumption for the audio range of frequencies.

> A third question: how much power does the ASM-1 draw? I'm a bit worried
> about my power-supply which can only go to 1 ampere. I know it will not draw
> that much, but there are going to be two of these, the moog filter and the
> paia vocoder which will all be fed from the same supply (hopefully). The
> reason I only want one supply is to keep the patching possibilities between
> these modules as highly possible.

You can use two powersupplies as long as they share the ground. This will work
with most powersupplies except some very odd once, but you are not likely to
have such an odd thing.

Cheers,
Magnus