[sdiy] That 2180 with modular cv??

Harry Bissell harrybissell at wowway.com
Tue Jun 28 19:37:11 CEST 2011


Thermal noise is still an issue, its the value of the resistor that causes the effect. OTOH
its 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 choice
using a 100K input.

H^) harry


----- Original Message -----
From: Dave Manley <dlmanley at sonic.net>
To: 'Synth DIY' <synth-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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