[sdiy] Real-world Eurorack signal chain advice...

Harry Bissell harrybissell at wowway.com
Wed Sep 15 18:26:17 CEST 2010

Design for the signals you intend to put through the devices...

The PAiA design was for 'low cost' certainly... but the audio at 500mV is a better
match than almost any modular system I know. I had to make special "attenuator" modules
for audio output, to get the levels down to where they should be.

Most FET, OTA based filters operate in low mV levels in their active regions... look at all
the 100:1 attenuators just before their inputs.

Also, boosting low level signals to get them into 'high level' devices adds a lot of noise
to the overall system, maybe more distortion as well...

I'd tailor the system to get the best S/N ratio I could, which in most cases would be to
avoid high amplification / high attenuation.

David... keep the spring out of your modular. You may play hell trying to keep it quiet unless
you shield it in a mu-metal box...  otoh it can be satisfying to whack your fist on top of the
cabinet and make the traditional 'thunder' sound :^)

H^) harry

----- Original Message -----
From: David G. Dixon <dixon at interchange.ubc.ca>
To: 'Barry Klein' <Barry.L.Klein at wdc.com>, 'Harry Bissell' <harrybissell at wowway.com>
Cc: synth-diy at dropmix.xs4all.nl
Sent: Tue, 14 Sep 2010 17:07:24 -0400 (EDT)
Subject: RE: [sdiy] Real-world Eurorack signal chain advice...

> Yeah, a good example of design for cost.
> But back to the original question - with such modules
> as spring reverbs, analog delays, multi-stage phasers -
> design for low noise or design for high level?

Hey, an on-topic SDIY posting!  Who'd'a thunk?

I have just the cutest darn little reverb tank sitting on my workbench that
I pulled out of a Kimball organ, and I'm just itching to put it behind a
panel.  I have no clear idea how to do this, so I'll be interested to see
how folks answer your question.

Harry Bissell & Nora Abdullah 4eva

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