Cgs synth

Hello,

I just wired up two VCOs (ver. 1.0 boards) and tested them. Everything works fine, except there appears to be a 1V DC offset on the sine output of both VCOs, the sine itself is 3V p-p. I double checked my wiring and the orientation of all significant components, changed the 240K offset resistor in the first part of the circuit to 580K to centre the saw wave around zero, put in another LM3900, but all to no avail.

Has anyone encountered similar problems?

Regards,

Johannes

Add a 47uF and 100k as per the output of the waveshaper (same as the ATSO
output). That will give you a waveform centered around 0V.

Ken

Ken,

sorry to get back to you on the group and shipping, very busy at my job but working on alll of them.

My idea to array transistor/resistors was to eliminate the need for 'military spec' transistors in the expo pairs.

In the dual slope gen you need matched pnp/npn pairs. I know arps used these, but never looked into how it. If you could built a handful of dual slope generators that could track and stick them in a box it would make a dreamy modular. I know it can be done with the time and parts, but not me. As an engineer, for one off or short runs i want to spend $2-5 more on a board, and fill it full of cheep generic parts.

Phil


To: cgs_synth@yahoogroups.com
From: sasami@...
Date: Sun, 13 Feb 2011 08:02:58 +1100
Subject: Re: [cgs_synth] CGS48 VCO - SINE DC OFFSET




























Add a 47uF and 100k as per the output of the waveshaper (same as the ATSO

output). That will give you a waveform centered around 0V.



Ken