WAYNE CHIRNSIDE wrote in a message to ROY J. TELLASON:

 RJT> No PLLs in there but there seems to be one heck of a lot of 4066 
 RJT> chips for some reason.    Outside of that,  just a few gates...

 WC> Quad digital switches IIRC that can be biased and used in preamps 
 WC> using different value resistors to control gain.

Yes,  I think perhaps my earlier attempt at messing with those (or maybe it
was 4016s) went poorly because I didn't bias them,  or run them off a split
supply.  I've got a little circuit here that's a charge pump to give you a
little bit of -5V from a +5V supply -- I'll bet that would do the trick and
if I feed it unregulated voltage then I could probably have pretty stable
dual 5V supplies,  which should be more than adequate for line-level audio
signals.

I wasn't thinking of switching in bunches of different resistors to do gain
control,  but rather some sort of pulse-width modulation.  Just gotta pick
a high enough frequency and figure out what sort of filtering needs to be
at the output end of things to make this work.

 RJT> After the CMOS can and the TTL can there was the linear can,  and I've
 RJT> found some interesting stuff in there.  I'm still sorting things out,
 RJT> but aside from the op amps and voltage regulators (more 7805s and 7812s
 RJT> than I'll probably ever use :-) there were some audio amp chips,  and
 RJT> some other ones I couldn't find anywhere (yet).  One I just snagged a
 RJT> datasheet for is the CA3094, apparently another OTA?  I

 WC> I believe it's an OTA with enhanced output characteristics.

Yeah,  a bipolar transistor with both collector and emitter available as
output pins.  It's unfortunate that the example applications in the data
sheet don't show me anything that I could do easier other ways.

 RJT> never did do too much with the 3080, the first of that sort of 
 RJT> chip I ran into.  It was hard to not have seriously heavy 
 RJT> distortion coming out of that thing,  I guess maybe some 
 RJT> application notes might help.  I wish I'd been able to snag this 
 RJT> stuff off the 'net ages ago! :-)

 WC> Yup, that too.

 WC> Wish I had the circuit for a negative resistance pulser by Forrest
 WC> Mims I once had from Popular Electronics.

He sure published an awful lot of stuff.  And much of it is in those little
books that you can get at radio shack,  maybe that circuit is in there?

 WC> Very short duty cycle but it pumped an amp or 2 through a LED
 WC> during that brief spike making for a very bright LED that could be
 WC> seen by detectors at great range.

 WC> Would like to pulse some white LEDs I've got now.

I have yet to get a hold of any of those,  or any blue ones.

 WC> White LEDs are available from the local Radio Shack for 4.95 each

That's a pretty hefty price,  and I don't remember seeing them there,  but
that's no surprise as I haven't spent that much time in there in recent
years anyhow,  and they typically charge more than most places for some
stuff.

 WC> or you can get the same thing in a battery operated keychain light
 WC> at Walgreens for 1.50 along with 2 3 volt lithium 2016 coin cells.

Too bad we don't have any of those around here.

 WC> The white LED has full length leads with the typical anode longer 
 WC> arrangement, the white ones have the 2 2016 cells which fit my 
 WC> watch and the blue ones have 1 2032 which fits my computer CMOS 
 WC> cell holders :-)

Do the white ones take more voltage to operate,  then?

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