[sdiy] my vco is TOO alive

[Dave Magnuson]

----- Original Message ----- 
From: "Dan Snazelle" <subjectivity at hotmail.com>
To: <nicolas3141 at yahoo.com.au>; "sdiy" <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, December 11, 2008 10:09 AM
Subject: RE: [sdiy] my vco is TOO alive


>
> after a long nights work i think the problem is WAY better.
>
> it was a lot of things and it still isnt perfect but....
>
> earthing properly between my two modular cabinets helped a lot. they 
> werent earthed together.
>
> (one cabinet is wood so the PSU is really only earthed to the panel in 
> some places while the top cabinet (separate PSU) is a metal case.
>
>
> anyhow...thanks to everyone's input i got it sounding great!
>
> i am also wondering how much the temp change (it does get cold in this 
> room at night) is effecting the circuit. MAYBE the circuit (EVEN PSU) 
> NEEDS TIME TO WARM UP??
>
> JUST WANTED TO SAY THANKS!
>
> if all goes well RINGO SNAZELLE is set to enter our world on sunday!
>
>
>

Hi Dan,

I've never heard of a PSU needing to warm up.   VCOs, however, sometimes do. 
Do you have a tempco resistor in your circuit?

I have some heated expo VCOs (EFM VCO4D) and they take about 5 minutes to 
warm up and stabilize. A drastic change in room temperature will make them 
drift a few cents.  My other temp compensated VCOs stabilize very quickly 
and drift less.

It's pretty funny to listen to the raw wave from the heated-expo VCOs.   The 
pitch keeps rising as the transistor array heats up.   It probably sweeps 5 
octaves from "cold" to "warm"

A totally uncompensated VCO will not have the long warm up time, but the 
pitch will drift much more with fluctuations in the ambient temp.

Of course, you also have to consider the PSU location in all of this.    If 
your PSU dumps heat into the VCO's "air space" it will cause things to drift 
as well.

Congrats on the (future) little guy!

Dave Magnuson