Questions about attenuators and mixers

Wild Zebra · Last edited by Wild Zebra on Mon Aug 06, 2007 12:38 pm; edited 1 time in total

Howdy y'all, I'm about to do a panel for my MFOS, VC LPF and VC State Variable filters and I wanted to know alittle more about attenuators and mixers. I thought about putting some passive attenuators on the panels. Are these acceptable for both audio and CV? Or do I need a DC mixer like this http://musicfromouterspace.com/analogsynth/dcmixer.html for CV's? I have a Ray's "cool new LFO" and it suggests using the DC mixer as a companion to control the CV levels.

I know it's all personal preference, but I'd like to hear if people prefer attenuators on the panels or as a seperate module. What are the pro's cons of using attenuators or mixers. What exactly is a inverted or non inverted output (example would help) Thanks. I'm still very much an infant at the modular synthesis game. Advice would be appreciated.

a.b.o.z. · Posted: Mon Aug 06, 2007 11:54 am Post subject:

you always have very good questions.
like you're reading my mind sometime.
i'm new to modular game myself also so im waiting for answer too.
cheers.

Dave Kendall · Posted: Mon Aug 06, 2007 12:10 pm Post subject:

Hi.

I guess it depends a lot on panel form factor, and available space per module. If you have room, then input attenuators and CV attenuators/mixers make life easier/quicker for setting up a patch. All the stuff you usually use with that module all on the front panel.

OTOH, if you're not using that module in a patch, then unless you have included separate INs and OUTs for each attenuator or mixer, then they can't be used for anything else. There's also a cost issue there - the unused pots/jacks are effectively wasted.

I've gone for a compact Eurorack format, where space is at a premium, so attenuators/mixers are in separate modules, which can be patched in where needed. Of course there's nothing to stop you from doing some normalising between these and your favourite modules, using maybe 0.1" pin headers and jumper cables connected to the switching contacts of the module jacks. That would cut down the front panel spaghetti a bit.
Hmmm, might try that actually.....

On a couple of modules, I added in a single attenuator with it's own (normalled) in and outputs just to complete the front panel space, if the control set didn't fill it up.
The CGS65 tube VCA will do this when I've finished it - with a feedback loop that can be used as an attenuator for something else, when not feedbacking.

BTW, the CGS04 is ideal for adding audio and CV mixers, being tiny, but flexible.

Someone cleverer than me will have to explain the inverting stuff - I must get back to testing a new module Smile

cheers,

Dave

Wild Zebra · Posted: Mon Aug 06, 2007 12:38 pm Post subject:

Thanks, for your opinion. I look forward to hearing more.

fonik · Posted: Mon Aug 06, 2007 1:09 pm Post subject:

Serenadi · Joined: Jul 03, 2007 Posts: 89 Location: Germany

Zebra,

I place as much attenuators into a module as I get on the faceplate.
I *hate* patching furthermore modules like mixers or separate attenuators if I only want one more input.

Of course, its a pricing factor, but compared with the full price of an extra module ...

Adding a furthermore input requires only a jack, a pot and a resistor, connected to the summing node of the input mixer, which is mostly present, anyway.

Most CV-inputs I construct as bipolar inputs, with inverted input at the counterclockwise side of the pot, zero at twelve o'clock, non-inverted signal at the clockwise side.
So I save extra inverting modules.

Internal prepatching I do only with signals like keyboard-CV or gate, or within a module, e.g. an S&H module with built in LFO (for triggering the S&H) where the LFO is prepatched to the trigger jack.

Wild Zebra · Posted: Tue Aug 07, 2007 7:31 am Post subject:

Thanks y'all. There's one question that kinda didn't get answered or maybe I didn't really ask. Is a passive attenuator i.e. a pot in the c.v. or audio path acceptable for both CV and audio? I mean I figure it would be, but just wanna know. There are so many different possiblities it's a little confusing. Like, what's the deal with the DC mixer I linked? Well I appreciate your thoughts so far you've helped set me on the path. Hmmm now what will I choose.....

EdisonRex · Posted: Wed Aug 08, 2007 2:19 am Post subject:

fonik · Posted: Wed Aug 08, 2007 2:30 am Post subject:

EdisonRex · Posted: Wed Aug 08, 2007 2:34 am Post subject:

fonik · Posted: Wed Aug 08, 2007 2:39 am Post subject:

sure, but nevertheless it would be handy. i thought of building a mixer with these switches to mix AC and DC signals to i.e. modulate a VCO. does that make sense?

EdisonRex · Posted: Wed Aug 08, 2007 3:29 am Post subject:

yes, that makes sense. It's the DC mixing that interests me anyway.