[sdiy] Tempco Resistor Question

[Ray Wilson]

Hi Richard

You can use the 1K tempcos if you change the voltage control input resistors
(R62 and R63) from 100K to 50K (49.9K 1%). The idea of the initial voltage
mixer is to get approximately 18mV out per each volt of control voltage in.
So 50K inputs resistors and the 1K tempco will give you 20mV per volt and
then the trimmers added with the mods let you fine tune the voltage fed to
the bases of the Q1 and Q2.

Cheers and good building

Ray



----- Original Message ----- 
From: <metamatic at webtv.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, June 17, 2004 7:41 PM
Subject: [sdiy] Tempco Resistor Question


> Hi everyone,
>
>  I'm building of of Ray Wilson's SoundLab synths, and I'm going to add
> the additional parts to make the oscillators 1V/octave compatible. I'm
> using a pair of 2SC1583s for the Q1/Q3 and Q2/Q4 pairs, and a 2K tempco
> resistor for R60 and R61. Since I still have a heap of 1K surface mount
> tempcos, is it possible to use two 1K tempcos in series? Will this
> affect the temperature compensation in any way?
>
>  While I'm on the topic of the surface mount tempcos, I've developed a
> convenient method of using them with a CA3046. I merely solder the
> tempco to one leg of the 3046, and use a bit of wire to connect the
> other end to another leg. For example, on some of Tom G's EFM boards,
> one side of the tempco connects to pin 2, and the other to pin 4. I've
> found that this is the most convenient method to use the SMT tempcos in
> this application.
>
> Richard Hess
>
> metamatic at webtv.net
>