[sdiy] Thoughts on AD823 for a 259-style timbre circuit

Aaron Lanterman lanterma at ece.gatech.edu
Fri May 29 05:14:31 CEST 2009

On May 28, 2009, at 5:22 AM, mark verbos wrote:

> What's wrong with CA3130s?

I got some impression from somewhere that they were out of production  
(although widely available still). But now that I look for  
confirmation of that impression I can't find any evidence to support  
that impression, so I'm thinking I must have got that mixed up with  
someone else.

Anyway, the main reason for my search for an alternative is that the  
CA3130 is a single op amp, so you need five of them to do the 259  
circuit, which takes up a lot of board space. I was hoping to find a  
quad (or dual if not quad) equivalent.

The AD823 came to my attention since it's a dual that claims to have  
"rail-to-rail" output like the 3130.

> These are used because they are rail to rail output opamps. I'd  
> guess you could use anything, but the results wouldn't be as crisp.

Indeed; the Easel is interesting since its timbre circuit uses garden  
variety RC4136s, so it's a little fuzzier as to the limits of its  
voltage output swings.

- Aaron

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