[sdiy] eml 101 VCO: continuously from tri to sqr to saw

[ニコラス・ケント]

On Apr 1, 2006, at 4:41 AM, ganesha wrote:

> Hi all,
>
> Probably a complete newbie question but I like the way
> you can change the waveform continuously from tri to
> square to saw on the eml 101 vco's. I would like to
> use that on a vco module I'm building myself, but I
> have a question about the schematic:
> http://www.krinkel.be/sdiy/eml101.jpg
>
> What kind of potmeter is used because it seems to have
> a connection in the middle where you can connect the
> square waveform?
>
> regards, Kris
>

That's what I've been asking about too the last couple days. Those  
pots in general, not the circuit you are looking at in specific.

As a whole the EML uses a bunch of those pots in the synth. So  
perhaps if "FA" is a really odd (or not)  taper maybe it was chosen  
because they had a supply of them and could cut down on the number of  
different parts? Sooner or later I'll try to measure one.

FWIW the "8va" in the schematic is actually a saw one octave up.  The  
knob's legend draws the entire range of output as
  tri -> "sloped square" ->square -> saw -> doubled saw
so it has at least one weird transition you've not mentioned (the  
last 3 waves)

So that brings to mind that perhaps a same-octave saw would do  
something less desirable??

If you are really keeping track OSC 1 doesn't have any mixing scheme  
and Osc 4 has a simpler tri to square option.

Further weirdness comes with the wave choices on the EML 100 (if  
anyone is keeping score)
cosine(?) -> square/cosine -> square
  tri -> square/tri (not the "sloped square") -> square

Of course in your case what you get with simplicity is to me is  
spoiled by not having CV control on any of this.

oh, and then the 100 (not the 101) gets their mixed multimode filter  
output to go LP->BP->HP->BR->LP via a pot
But I don't have the schematics to the 100 filter, and as usual no CV  
control of that.
The 101 does a simpler LP -> BP -> HP

P.S. you can get the entire 101 schematics off the EML yahoo group.  
I've still not sourced a set of 100 schematics though I have some  
pages marked "100 and early 101" apparently for servicing  
transitional 101 units.

ndkent