I tried building the EFM VCA5b which is almost identical to this with
unmatched transistors, and the output was kind of noisy, and didn't
resemble the input very closely with full gain. I think there was some
CV crosstalk as well. As soon as I put a 2sc1583 in place of the
transistors it worked a treat. Although I also changed the rest of the
circuit to make it like the CGS64 too (bias trimmer and so on). Oh, and
I couldn't get it completely silent either! I'd say go with the matched
pair for sure.
James
Jorrit Tyberghein wrote:
unmatched transistors, and the output was kind of noisy, and didn't
resemble the input very closely with full gain. I think there was some
CV crosstalk as well. As soon as I put a 2sc1583 in place of the
transistors it worked a treat. Although I also changed the rest of the
circuit to make it like the CGS64 too (bias trimmer and so on). Oh, and
I couldn't get it completely silent either! I'd say go with the matched
pair for sure.
James
Jorrit Tyberghein wrote:
>
> Hi all,
>
> Why exactly does the CGS64 (VCA) require matched transistors? What
> happens if you just use random transistors? In what way will the VCA
> not work correctly then?
>
> Greetings and thanks,
>
>