[sdiy] Unstability of oscillators and psychoacoustic qualities

[Magnus Danielson]

Dear all,

If you recall, much have been discusses about the unstability of oscillators
and that this or that oscillator sounds "cold" where as this and that
oscillator sounds "warm". Similar aspects have also been attributed to filters.

Now, in one end we know that unstability in frequency is a bad thing, since
then we need to retune the damn machine. The classic is the MiniMoog which you
had to turn on at least half an hour before the gig start, and if you forgot
you have a hell to keep it in tune all of the time.

Another aspect is that a certain unstability is claimed to make the sound more
"alive" or "warm". The lack of this unstability is also claimed to make the
oscillator "cold". It is interesting to note that certain filters is also
claimed to be "cold" or "warm", such that a "cold" oscillator can be
compensated with a "warm" filter.

So far I am mostly summing up what have been discussed on this list and many
others over the years I've read them.

Now, in my professional life I work with stability of clocks in many signals
from 4 kHz up to 2.488 GHz. In that line of work there is well established
methologies to measure the unstability of oscillators and signals. Many will
know this as jitter and wander where as other will know it as phasenoise and
Allen deviation. There is great tools to measure these things and I just
happends to have access to one of these frequency-counters on steroids that
can do this.

However, what is the goal of measurement? Well, I would like to learn what form
of unstability which sounds "cold" and which sounds "warm". I.e. it would be
nice to quantify by both reasoning and by measurement/listening-test what is
"cold" and what is "warm". Interesting would also to know when things go
overboard from "warm" to "too damn hot".

Have people dug into this allready?

I've considered doing this for quite some time, but I just discovered that I
got alot of free time ahead of me, so why not do something usefull of it?

Cheers,
Magnus - you know, that crazy Swede...