From R.J.Green-SE0@computer-science.birmingham.ac.uk Fri Jan 29 13:43:51 1993
From: R.J.Green-SE0@computer-science.birmingham.ac.uk
Date: Fri, 29 Jan 93 17:47:09 GMT
Subject: Flowing Sinewave Bliss
Status: OR


The story of the ISIS:
	I met this bloke at raves and events. I invited him over for a sunday
afternoon jam and he brought...

	A Roland D4 drum machine. (Nice, as we use Amiga + Octamed)
	A Digital Reverb (Forget the name)
	This ISIS thingi.

He left the ISIS in my capable hands and as soon as I'd worked out what all the
filters do and which ones affect which others, it was all a case of tuning the
8 notes and reverbing it. Purest acid.

Now that's about the range of my knowledge about it. 70's Maplin Kit. But it is
nice to use. I WISH I could find schematics of it as I've got an ElecEng mate
who is ITCHING to redesign this with sliders instead of knobs. Still, he's got
a reverb pedal to make first...

Homemade is the ONLY way to go. Home stereo panning with a pair of summing
Op-Amps and a variable Pot. This sorta thing. All live, all direct and always
different every time. Kinda scary when you go into a live situation with an
audience. Gotta dump it to tape else you'll never remember how it was set up.

The ISIS: From Left to Right...

Top Row -	8 knobs (black) for the pitch of the 8 notes. Probly about 4-5
          	octaves. Very dodgy to use these. Tiniest movements and they're
		not linear either!

Middle Row -	Overall pitch - affects all the system. Generally best left
			 alone except for days beginning with a Q,Y or K
		Volume of Oscillator. (Doesn't affect Resonance!)
		Modulator freq. From dead slow to about 100 hz?
		Filter (The main filter) Play with this bucko like a clit!
		Resonance (with a black biro mark for the howling point!)
		Attack of note (usually zero, produces clicking noise.. ooer)
		Speed of pattern repeat. From 10 sec/note to 40 notes/sec

Bottom Row -	Square Wave Pitch Adjust. Transpose half the pattern up some,
			half the pattern down the same amount. Sorta does
			a key change if you're lucky. Use with care.
		Saw wave pitch adjust. Sorta wibbles the notes. Useless except
			for making a mess of the notes in which case it's kind
			of nice.
		Modulator Pitch Amount. I'm sure there's a good word for this
			but I'm buggered if I can think of it. The amount that
			the mod. mods by.
		Modulate Main Filter. Crank it up & Leave it wibbling on its
			own. Slow Modulator, medium filter mod. Leave it to do
			it's own thing. Niiiice.
		Brightness of the filter. (Use with edge of howling resonance)
			Best used with Filter and Resonance for accurate edge-of
			square-wave-effects. Y'know - farty noises.
		Decay of Note. (Usually pretty small) It's a bit sensitive on
			this length of note. Again, non-linear POT.
		Length of pattern. From 1-8 notes. 5 is good for head fucking.
			Especially when synced with a breakbeat. Digital switch
			like on an old washing-machine. Click..click..click..

Other knobs - 	Overall volume O/P
		Switches for on-off (Doesn't work), internal and external VCO,
		and internal/external Sync.

And that's about it. It's got some pretty patterns scratched onto the aluminium
and wood casing, like the on/off led has an egyption eye made from it and it has
a cosmic Om scratched on it too. Proves it's roots in 70's hippydom.

I don`t think I can be more precise than that at the mo. Like I say, it's not
mine.... boy do I wish!

- Robin trying to be helpful.

P.S. What EXACTLY are the knobs on a 303? What are good settings for them?
     A Digital software version shouldn't be so hard. Just a little filtering
     Maths. Humm....