PLAN B analog blog

Mults are not mixers, they're splitters. One requires a summing mode
with some sort of current limiting.  There are passive mixers (not
that good) and active mixers (the correct way to do it).  Passive
mixers will do the job, but the signals will effect each other.  Let's
say you have an internal passive mixer for a bunch VC sources into a
VCO (think Arp 2500, which did use passive mixing for this).  Let's
say there is an LFO and a sample and hold routed into two of the
passive mixer's inputs. Let's say that sample and hold is also going somewhere else in the patch.  The LFO signal, which is only routed to the VCO will also effect the sample and hold wherever it's routed in the patch. With an active mixer, each signal is isolated from the others - signals routed to other sources will not each other.  

Splitters are nothing more than a bunch of wires which are tied
together.  Using this configuration as a mixer is plugging the outputs
of a bunch of modules together.  Remember:  first golden rule of
modular:  Outputs to inputs, not outputs to outputs.

In regard to the Dynamic Mult, you can use it as a passive mixer if the signals are kept low, meaning the pots aren't cracked to far up.  In application this is a passive mixer. But the higher you turn those knobs, the less resistance between the summing nodes and there will be a point were you've got a dead short - a bunch of wires tied together and this is when you'll start damaging your equipment.

Using mults as mixers will work for a period of time, but after time
you will blow the output drivers. Plan B uses 1k impedance, better than nothing, but low.  So it'll work for a while, but you are stressing the shit out of the output drivers. 

Best rule of thumb - don't use mults as mixers!   



--- In PLAN_B_analog_blog@yahoogroups.com, Christopher Jacob Recording
Device <I.AM.USING.THE.INTERNETS@...> wrote:
>
> Ok, so this may have come up before I joined the conversation but
I've been
> wondering for some time why on the Plan B website you've advised
people not
> to use the Dynamic Mult as a mixing device? Is there a practical or
> technical reason for this? I ask because I'm planning out a system
and it
> seems to me that having a mult that can attenuate would be a good
choice for
> mixing with as well. I know a lot of multiples aren't specifically
designed
> to mix signals and control voltages but why not? And can anyone
suggest a
> better way to use that 8hp if there is a practical reason why I
shouldn't
> consider the DM as a good choice here?
> 
> Thanks,
> Chris
> 
> -- 
> "War will end when people refuse to fight"
> --Anonymous
>