[sdiy] mults and mixers

[Dave Magnuson]

At 11:01 AM 8/15/03 -0400, john mahoney wrote:
>
>What are multiples, 4-input control voltage mixers, and attenuators? (An
>easy point of reference is the Moog CP-251, it has all those:
>http://moogmusic.com/detail.php?main_product_id=12)
>
>Is an attenuator just a pot? (1 Meg linear taper?)

Yes, and attenuator is typically just a pot.  1M would work, but I tend to
use 100K.  Buffered ins and outs are nice, but not necessary.  The buffers
let the modules on either end see a constant impedence, where an unbuffered
pot will change the loading as you adjust the pot.  Without buffers you may
notice some odd behavior with certain modules (waveform distortions, etc).   


>Is a mult just 4 jacks wired together, or do you need buffers/etc.?


A mult is generally unbuffered.  It takes one signal and allows it to be
patched to multiple destinations.  Buffering is ideal, since plugging in a
new cable won't effect the load that the other modules see.  If you have an
unbuffered mult you may notice a pitch shift when patching to a VCO CV, for
example. Although buffering is ideal, it's not that common 


>Is a 4 input mixer just a mult with attenuators?


A mixer is the reverse of a mult.  It allows 4 sources to be mixed and sent
to a single destination.  This is almost always an "active" module with an
opamp stage or two (where mults are generally passive with nothing but
inter-connected jacks)


Hope this helps,

Dave


Resonant Frequency:
resfreq at hoohahrecords.com
http://www.hoohahrecords.com/resfreq/index.html
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