questions from a newbie

[Roel Das]

Comments inline.

> 1)Fatman :
> I've recently soldered together the Fatman kit. Naturally, something went
wrong,
> and I'm now in the process of figuring out how to get the sucker working.
The
> symptoms : the gate LED doesn't lite when I send in a MIDI note (the MIDI
LED
> does, however), and there is no output, beyond what sounds like two out of
synch
> saw waves playing some middle-end note (very faint, and audible only when
I
> crank the output all the way up). I've done quite a bit of probing, and
both
> oscillators are working fine, and I'm getting the output from the VCF pots
that
> I should be (lug two of R56, the 1/2 mixer gives me nothing though). Any
> thoughts, anyone?

I don't know much about the fatman, but the reason for this problem seems
clear:
the midi conversion is not working properly. This could be due to a wrong
configuration or something. The VCA won't let anything through if the gate
is low. The sound that you do hear is probably leaking through the VCA with
gate low.

> 2) concerning different op-amps...: is there any difference between
different
> op-amps, other than gain? If this is so, then it seems to me that any
op-amp can
> be used anywhere, certain ones are simply more efficient.

There are quite a few differences between opamps. You could write books
about opamp characteristics.
You really should do some reading on this... You can find some of the most
important criterias for opamp selection in the archives of the list. Last
month there have been a few interesting discussions on favorite opamps and
quad opamps (=4 opamps in one package). I certainly learned alot from these
mails...

The book we used at school last year: 'design with operational amplifiers
and analog integrated circuits' by Sergio Franco. (available from McGraw
Hill)

>
> 3)just what does an LDR do?

LDR stands for Light Dependent Resistor. The value of this resistor is
dependent on the amount of light that falls on it... What's in a name...
(more than in an abbrev, that's for shure...)

A book on sensors they feed us this year: 'sensors and signal conditioning'
by Ramon Pallas-Areny and John G. Webster, (available from John Wiley &
sons, inc.) But this is quite heavy literature if you only want to know what
an LDR does...

> Many thanks....

My pleasure...
I really enjoy the moments that I'm not asking questions myself.
Roel