ASM-1 osc.sync issue

[Magnus Danielson]

From: "Debby and Gene Stopp" <squarewave at jps.net>
Subject: Re: ASM-1 osc.sync issue
Date: Sun, 27 Feb 2000 22:54:21 -0800

> Hi all, sorry for the delay, been out of town again....
> 
> Regarding the sync issue - don't use the sawtooth output from one VCO to the
> sync input of the other VCO, use the pulse output.
> 
> The sawtooth does not provide a good sync signal. The pulse wave is much
> better and will give the classic hard sync sound.
> 
> The sawtooth as generated by the VCO core rises from 0v to +5v and then
> resets to 0v. I add a level shifter afterwards which produces a sawtooth
> between -5v and +5v , and the waveform is inverted in the process. The
> output waveform really starts at +5v and ramps down to -5v, then resets to
> +5v.
> 
> The sync input of the VCO allows an external signal to change the reset
> threshold of the VCO comparator. A negative-going pulse is needed to lower
> the threshold so that the VCO sawtooth resets sooner than it normally would,
> forcing the edge alignment with the external signal which is also referred
> to as "sync". A sawtooth going the "wrong way" will provide poor sync
> behavior.
> 
> So, use the pulse wave. I discovered this after I had already created the
> ASM-1 documentation. If I ever release a new revision of the documents, I
> will include this advice.

I've just updated the ASM-1 homepage to have the following note at the VCO
text:

Note:
	The sync input should be feed with a pulse wave and not a sawtooth
	wave in order to operate properly. So, for propper sync operation,
	do not feed it sawtooth (or other non-pulse waveforms)!

Will that suffice?

Cheers,
Magnus