[sdiy] Unstability of oscillators and psychoacoustic qualities

[Magnus Danielson]

From: "jhaible" <jhaible at debitel.net>
Subject: Re: [sdiy] Unstability of oscillators and psychoacoustic qualities
Date: Tue, 24 Sep 2002 09:36:03 +0200

Hi Jürgen,

> >We have already learned something important and I haven't even started
> >measuring anything!!!
> 
> That's always a good thing, *especially* with synths.
> It's quite impossible for me to make any serious measurments
> on a working synth, because I always end up playing it rather
> than making scientific measurements.
> That's the good thing about theory (and simulation) - paper
> and spice don't distract us that way.

Hmm... interesting problem. I for one have as much playing both types of
instruments... ;O)

> >I have to some degree avoided the use of the term "fat" in these
> discussions.
> 
> What is the difference between "warm" and "fat" for you?

Well, if I where to separate it, I would say that "warm" is more organic
where as "fat" is more excessive than nature normally would allow.

Did that make sense?

> (It's all just words, so I guess there is nothing such as right or wrong
> here.
> Just curious how you use the words. BTW, when I switch the modulation
> off on the Lambda Strings - bringing them to a locked condition
> immediately -
> I like to call that sound "thin" rather than "cold". This "thin" sound makes
> a wonderful source for further processing with a resinant phaser, too.)

Well, maybe you see why I originally decided to only use "cold" and "warm" as
the main words, since then we could avoid idiotic debates on "cold" vs. "thin"
and "warm" vs. "fat" vs. "lush". I selected two words which I thought where
enought descriptive and quite distinctive (althought "hard to reach" languague
wise) characteristics.

I think "cold" is more the opposite of "warm" and "warm" really mean less
sterile. Sterile is usually synonymous with "cold".

As for "lush" it may be a variant of the same pheonomena, as I percieve the
meaning at least.

Similarly, "fat" is something where I perceive that there is more of
"something" from what I would call "warm". Think of a 70thies TD base tone
which lies there sweeping like a "warm" tone, then becomes sharp (tonal wise)
to become quite "fat".

> >My point is that I think the issue has not been as clear to designers other
> >than "I guess it is a good thing to keep it down" and not "I need to keep
> >thermal noise to this leverl to make a warm (or cold) oscillator". I think
> >there is a high risc of afterconstruction, thus assuming that certain
> thoughts
> >where in place even when they where not.
> 
> My opinion exactly.
> 
> We can only speculate (or ask the designers!). But I'm pretty sure that
> it was not intentional on 1st generation synthesizers in the 70's.
> I think Yamaha and Korg used linear VCOs because they wanted to avoid
> expo converters, not because they calculated that there would be a pleasant
> low frequency mistracking from remaining offset voltage, for instance.

Indeed.

> And I remember Bob Moog said the noisy PSU was a lucky accident
> to prevent the Minimoog VCOs from locking.

Right. There where a whole set of accidents and different design philosofies
which created differnet solutions experiencing different character. Question is
just how much experience where taken in at the time.

Cheers,
Magnus