Hi all! Some questions...

[Stopp,Gene]

Hi Chuck,

I'd like to respond publicly - old timers on this list already have
heard what I'm about to say, but it may stimulate some comments which is
always fun.

For the test setup, I'd recommend the following:

1. A temperature-controlled soldering iron
2. A Digital Multi-Meter (DMM)
3. A bench power supply
4. An oscilloscope
5. One of those white plastice prototyping boards that you stick parts
and wires into
6. A couple parts cabinets filled with components

The merits of a temperature-controlled soldering iron far, far outweigh
the cost increase over a non-temp-controlled iron. The cheaper kinds are
okay for old radios and hobbyist stained-glass, but for modern chip work
you must have temperature control. You can get a nice Weller
temp-controlled for $80-90.

You can get a perfectly decent DMM at Radio Shack. You may not use it
all the time, but it will really come in handy for mundane tasks like
checking resistors and pots and things like that.

The power supply can be expensive. You will need at least three
voltages:  +5, minus 12 or 15, and plus 12 or 15. If the plus and minus
supplies are adjustable, so much the better. You might be able to find a
used or surplus fixed-voltage supply (like a Power General or something)
for a good price.

The scope is not an option in my opinion - it is essential. Find a used
one, try to keep it down to two or three hundred dollars. If you see a
dual-trace with at least 20 Mhz bandwidth for five hundred, and it's in
good shape, get it. A couple things to check when buying a used one -
make sure the traces are fairly bright and in focus, and make sure the
horizontal trigger works. Not only will the scope allow you to learn
about what goes on in a circuit, but it is also needed to troubleshoot.
Without it you are just guessing. There's really no two ways about it.

The prototyping board is the best way that I can think of to learn about
designing your own synthesizer circuits. The parts of course are needed
to stick into the prototyping board.

As for the MIDI processing applications, there are several approaches
and everybody has their own preference. My particular approach is a
result of the fact that I happen to have a whole bunch of PC hardware in
boxes in the garage.

A PC motherboard can be adapted to dedicated MIDI projects quite easily.
For MIDI I/O, you can get a cheap sound card these days for less than
$20. You will need to find a game-port to MIDI cable for it - there's
active components inside the cable, so it's actually better to buy one.
For connection to the outside world, you can use the parallel port. This
can be set up for reading and writing 8 bits wide, with 4 additional
signals for external circuit control. You can always add another
parallel port for double the signal path width. Most motherboards 386
and up can be configured in BIOS to ignore the lack of an attached
keyboard at boot-up time, so you can just build the motherboard into
something and let it run like any other microprocessor project without a
user interface. Of course, you can add jacks for a
keyboard/monitor/mouse for when you do want to interact with it. You
will need at least one boot device, but this can be a simple floppy
which is only a few bucks these days. Hard drives and other frills are
optional but similarly priced.

Hang out behind a computer store and watch the dumpsters. I have several
*working* motherboards that have come to me this way, all the way up to
Pentiums! For the operating code, you can just use QuickBasic, which
comes with DOS. On a 486 this is actually fast enough to run an 8-port
DAC from MIDI without any problems timing-wise - I have it running to
prove it. I did write an 8-voice polyphonic experiment, and I did see
some lag time with that, but I have a QBasic compiler and once I
compiled to an EXE it was as fast a lightning. So C code for example
compiled to an EXE should be plenty fast, even on a 386/25.

As for the actual code algorithms, that is another topic, perhaps suited
for a new thread....

 - Gene

 ----------
From: Chuck Lutz
To: synth-diy at mailhost.bpa.nl
Subject: Hi all!  Some questions...
Date: Tuesday, February 10, 1998 11:04AM


Hi folks,

My name is Chuck Lutz, and I've been a lurker on this list for a
long time.

<snip>

Would anyone have some recommendations on putting
together a basic setup tailored to this sort of work?  Scopes, power
supplies, meters, etc.?

2) I'm starting to think about various MIDI hardware applications...

<snip>

Well, I hope this isn't too long of a first post!  Reply publicly if
you think it would benefit all, otherwise, feel free to just drop me
a public line if my requests are common knowledge to list veterans.

Thanks a lot!

Chuck Lutz