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

Barry Klein Barry.L.Klein at wdc.com
Tue Sep 14 23:00:47 CEST 2010


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?


-----Original Message-----
From: Harry Bissell [mailto:harrybissell at wowway.com] 
Sent: Tuesday, September 14, 2010 10:42 AM
To: Barry Klein
Cc: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] Real-world Eurorack signal chain advice...

LOL... the PAiA 2720 had very different audio and control levels,
500mV for audio, 0-5V for control

otoh, there was not much difference between them electrically... especially
~any~ control signal you tried to use ended up on your audio.... :^/

(btw dave dixon, thanks for the new emoticon idea :^)

H^) harry



----- Original Message -----
From: Barry Klein <Barry.L.Klein at wdc.com>
To: synth-diy at dropmix.xs4all.nl
Sent: Tue, 14 Sep 2010 13:18:31 -0400 (EDT)
Subject: Re: [sdiy] Real-world Eurorack signal chain advice...

I'm really surprised this isn't discussed more.  Most effects circuits are
designed for lower level signals.  If you design for the higher you usually
pay a big price in added residual noise.  (You add resonance feedback and it
clips against the supply rails.)
It all depends if the output will be used as a control voltage I guess.
Usually these kinds of things are the last in the signal chain and
remain low level so really should be optimized for use with such signal
levels.  I'm not aware of a modular taking this optimized approach though - 
separating signal generation and manipulation (high level) from filtering
and effects (low level).  Or maybe they do and its just not discussed?
I remember wondering about this - what 30 years ago? - when I was messing
with analog delay parts, multistage phasers, and spring reverbs.  It was
why the effects in/outs in the Music Man amps I worked on at the time sucked
- I was forced to work with signal levels too high. 
 
Barry

>
> +/-10 Volts is considered to be a good, wide-range CV. Fine.
>
> Most VCOs/LFOs are quoted as outputting 10V PP. In reality though, even
from the few modules I have here, that could mean an output of anything
between 5v PP and 15V PP.
>
> So - would you prefer:
>
> 1) A module that could handle 20V PP (i.e. +/- 10V PP regardless of
whether it was CV or a *hot* waveform) and provide some sort of on-board
amplification/biasing for smaller/quieter waveforms.
>
> 2) As above - but presume that the serious user will have their own
ways/dedicated modules for handling amplification/biasing/attenuation, etc.
>
> 3) Go with the quoted *standards* of 10V PP for waveforms and provide some
sort of on-board attenuation/biasing for bigger/louder waveforms.
>
> 4) As above - but presume that the serious user will have their own
ways/dedicated modules for handling attenuation/biasing, etc.
>
> Seems like #2 is the most sensible 'big picture' solution to me but the
whole modular/Euro thing is still pretty new to me so I'm still working out
workflow, etc. There's possibly no right or wrong to this - answers
appreciated as always.
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Harry Bissell & Nora Abdullah 4eva



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