[sdiy] Memorymoog VCA/VCF experience

[Aaron Lanterman]

Brian got it working, but I wanted to write back to Harry's notes anyway.

On Sun, 17 Dec 2006, harry bissell wrote:

> May I enquire if you are building on a "White nylon slab-o'-trouble" 
> (solderless breadboard) ? If so you may be looking for a hidden open or 
> short circuit.

Yup. They're standard issue. I know they have problems (and the students 
know it too, especially when their boards have seen a lot of use)... but 
for running around helping six different students telling them to try 
different things, it's hard to beat the speed and convenience of the 
breadboards. If they had to solder and then desolder and resolder every 
time they made a change... I can't imagine that.

> DID YOU use a dual channel scope ?  If you used a single channel scope 
> then each time you look at a different point, it will trigger and MAKE

Yup, being able to do dual traces (and XY plots on a waveshaping project) 
was invaluable.

We have some nice scopes in lab and I will say it took a while for 
everyone to get the hang of truly exploting their power. In particular, 
the "autoscale" feature on them is a bit wonky... often I and students 
would give up and think the circuit was broken since "scope couldn't find 
active signal," but we'd manually twizzle the knobs and be able to find 
it; also the autoscale would often find high-frequency noise, and then 
you'd have to go look for your actual audio.

> NEVER believe the test equipment until you prove it... (measure something you 
> are SURE of)

That's been very important. All the best most well-maintained equipment is 
in the junior labs (instrumentation and electronics labs); the senior 
design lab has quite a lot of cast-off equipment and we've learned a good 
portion of it is hosed in one way or another. One of the scopes just shows 
60 Hz line current no matter what you do.

But, when I first joined in 2001 there wasn't a dedicated senior design 
lab at all, so we're glad to at least have the space now.

I'm learning so much running this course. I'm teaching a grad class on 
signal processing for antenna arrays this Spring... not sure when I'm 
going to do the synth class again. Hopefully soon. :)

- Aaron