Surface mount synths??

[Joachim Verghese]

On Wed, 10 Jul 1996, Kevin Lightner wrote:

> Any thoughts on making a surface mount, all analog "voice" board, similar
> to an SEM or ASM-1?

I've played with that idea too. I even designed a filter board for the
Odyssey which combined two of the original filter designs (4023 2-p
biquad and 4035 4-p ladder) into a single 4035/4075 compatible module.

The main problem with DIY surface mount technology is in prototyping.
Using SMD components is space saving only if you use fine-line (8 mils)
PCB tracks and small vias (holes for connecting top and bottom side
copper tracks). Clearly, these kind of boards can only be produced
at professional prototyping houses, which is expensive.

Also, some components do not exist or are hard to get in SMD form -
tempco resisitors were already mentioned, but also plastic capacitors.
NP0 ceramics are good for audio, but values larger than 1000pF are hard 
to obtain. X7R types have larger values, but are generally not recommended
for audio.

-joachim