[sdiy] That 2180 with modular cv??

Dave Manley dlmanley at sonic.net
Tue Jun 28 21:52:12 CEST 2011


Ignoring the offset issue...

Realistically, how much thermal noise does a 100K resistor generate, and is it important in a unity gain circuit, with typical synth CV levels?  If we're talking micro volts of noise in a CV path, does anyone care?

-Dave

 On Tue 11/06/28 10:37 AM , "Harry Bissell" harrybissell at wowway.com sent:
> Thermal noise is still an issue, its the value of the resistor that causes
> the effect. OTOHits just a waste of an otherwise good opamp.  NE5532 and 5534 have pretty
> bad input voltage offset specs as well, so they are poorly chosen for DC amplifiers. Probably would work 'ok' but a
> TL072 would be a better choiceusing a 100K input.
> 
> H^) harry
> 
> 
> ----- Original Message -----
> From: Dave Manley <dlmanley at s
> onic.net>To: 'Synth DIY' <s
> ynth-diy at dropmix.xs4all.nl>Sent: Tue, 28 Jun 2011 13:11:38 -0400 (EDT)
> Subject: Re: [sdiy] That 2180 with modular cv??
> 
> On Tue 11/06/28  9:05 AM , "David G Dixon" dixon at mail.
> ubc.ca sent:> > Dan wrote:
> > > 
> > > > http://m.bareille.free.fr/modular1/vca_dbx/mb_dbxvca.htm
> > > 
> > > NE5532s and NE5534s with 100k resistors.
> > *sheesh*  Thermal > noise and DC offsets, oh
> my!> 
> > Not to mention that the lights will dim when you
> turn it on!
> Note however, looking at the pics and notes, Marc used FET-input op amps in
> his build.
> There's no gain in the areas with 100k resistors, is thermal noise an
> issue?
> -Dave
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> -- 
> Harry Bissell & Nora Abdullah 4eva
> 
> 
> 
> 


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