[sdiy] Unstability of oscillators and psychoacoustic qualities

[media.nai at rcn.com]

>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".

Yes, for about 10 years, and in the course of that time, most of them have
been based entirely on subjective opinion, biased or otherwise.  In
general, people will defend the oscillators they own, and attack
oscillators they don't.  Such seems to be human nature.

>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.

Yes, which is one reason why my MiniMoog is going into storage unless
someone shows up with a wheelbarrow full of money :)

>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".

Imho, that is an over generalization -- stable analogue often sounds fine,
and shaky digital almost always sounds terrible.

>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.

Then in that case, I would analyze waveforms and waveform stability, as
filters have no effect on frequency stability.

>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".

I would qualify "warm" as having the characteristic of acoustic
instruments, and use them as your basis of quantitive analysis rather than
"warm" electronic instruments.  I would define "too damn hot" as out of
tune.

>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?

The most useful goal would be to come up with mathematical explanations,
for that seems the only way to have any chance of settling the issue.

I look forward to hearing your results.