Tuning the FAT MAN

Ian A. Vine phone UK 0171 419 3450 iav at hep.ucl.ac.uk
Tue Jan 21 09:44:28 CET 1997


> But now that I am in a band my fellow musicians want it tuned.  All of the
>trim pots I think are bad and I will be soldering 3 1k pots and 1 10k pots to
>the back of my custom box.  I love this thing but it just doesn't want to be
>tuned.

	After I discovered that I'd mixed up wiring between the pitch
	and glide control the tuning was a lot easier! The only clue
	I got that anything was wrong was no slow glide times and not
	much pitch range. Other than that (no insult intended) is the
	soldering ok, I would be suprised if the presets were dodgy.
	Once the presets were tuned I haven't touched them since, just the
	occasionally tweak to the pitch control and that's usually after
	I've knocked it by accident.

>Question #2  has anybody made a VCO from a 555 timer.  There is a radioshack
>book that gives a real basic schematic of one.  Is there a better one that I
>can build for under $30?  I know that the CEM chip costs $15 dollars from
>onchip but I am really broke.

	If you're going to use the VCO with the fatman why not take
	a look at the schematics. The only problem with the fatman
	VCO and the one in the radioshack book is that the output
	frequency is linear with control voltage whereas most systems
	 
	use v/oct control volts (ie the vco frequency changes exponentially
	with voltage).

>Question #3  This may sound like the stupidest question there is but, do you
>need an envelope follower to make a vcf work as a stand alone unit for
>connecting it to a sampler output ( like a EPS )  or should I use an
>amplified E.Q. with a mid range sweep combined with a limmiting circuit?
> What would be the most effective and cost efficient one.

	I guess you want to filter the sample. One way would have a VCF
	with an envelope generator which is triggered either by the smaple
	sound or via midi from the sampler (or maybe even a good old gate
	signal). A cheap way to get this is to use the fatman, you'll need
	to add an audio input to the filter. I don't have the schematics
	to hand but its pretty easy to patch into the fatman

Ian



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