Archive of the former Yahoo!Groups mailing list: MOTM

--- Tony Allgood <oakley@...> wrote:

> But I would hasten to add why we really need to be 'hugely'
> accurate at DC for an external mixer. This only really applies
> for VCO pitch. The MOTM VCO has a 1V/oct input which
> are used for the pitch CV already.

----- Original Message -----
> From: alt-mode <alt_mode@...>
> I second this approach. I'd rather have a good audio mixer that does
> DC than a hugely accurate DC mixer or a very expensive mixer that
> does both. The voltage summers on the inputs of the modules should
> do the accurate DC mixing. When I'm mixing control voltages through
> a mixer, the offset and drift are usually not as important because I'm,
> well, mixing up a bunch of control signals and probably don't care as
> much about 1V/oct scaling, etc. Besides, a little drift and non-linearity
> can be very creative now and then...
> Eric

I agree gentlemen. "Usefulness" and "do you need this or that?" should be
the basis for design anyhow. But, I thought the discussion about how one
might go about it was interesting and worth having. I think we will all be
happy with the compromise approach Paul will choose.

> Tony Allgood wrote:
> Another issue for mixers, particulary at DC is the gain. This is worse
> to set up accurately in a reversible attenuator system. In other words
> accurate calibration of +1 and -1 settings.

Yep. So, you would have a mixture on inputs -- some or most reversing and
maybe one or two that are not reversing. Kind of the same approach Paul
uses with FM inputs.

Larry H