[sdiy] LT1228 / 13700 for VCA

[Tim Parkhurst]

Our own Jörgen Bergfors has a rather interesting "VCA Shootout" page
http://hem.bredband.net/bersyn/vca.htm

In this comparison, the 13600 and 13700 come out very well. There are no
3280s in the shootout, but there are 3080, SSM2024, and several discrete OTA
circuits represented. Looks to me like the 13x00s work well for audio VCAs,
so save your 3080s and 3280s for applications where the higher performance
and linearity are necessary (VC mod depth, VCO cores). 

Also, for more OTA info, here's a repost of a message I sent a month or so
ago:

++++++++++++
Just wanted to report what I found from a recent Google search on OTAs

Two interesting papers on theory and applications, both by
Dr. William R. Grise

Application of the Operational Transconductance Amplifier (OTA) to
Voltage-controlled Amplifiers and Active Filters
http://et.nmsu.edu/~etti/winter98/electronics/grise/wrg.html

Operational Transconductance Amplifiers (OTA) for synthesis of
voltage-controlled active-filter tuned oscillators
http://et.nmsu.edu/~etti/fall98/electronics/grise/griseota.html

*****************
Mouser has the following:
13600 (NJR brand)  16 DIP  .42 ea
13600 (NJR brand)  16 DMP (surface mount) .53ea

13700 (NJR brand)  16 DIP  .72 ea
13700 (NJR brand)  16 DMP  .41 ea

Digi-Key has:
13700N  16 DIP  $1.43 ea
13700D (NJR brand)  16 DIP  .99ea
13700M (NJR brand)  16 DMP  .81 ea

*****************
Jim Patchell has CA3280s listed for sale at $4.00 ea, 
http://www.oldcrows.net/~patchell/parts/parts.html

and Mouser has them at $5.23 ea (ouch).

+++++++++

Tim (I shot out my VCA and it still didn't sound any better) Servo


> -----Original Message-----
> From: Ray Wilson [mailto:raywilson at comcast.net]
> Sent: Friday, May 20, 2005 4:36 PM
> To: Gabriel Lindeborg; synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] LT1228
> 
> I think the LM13700 chip is excellent. In my opinion it is miles better
than
> the CA3080 and definitely on par with the CA3280.
> They are relatively inexpensive and just a great chip. I know I'll hear
> about this one.
> 
> Ray
> 
> 
> 
> ----- Original Message -----
> From: "Gabriel Lindeborg" <gabriel at lindeborg.org>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Friday, May 20, 2005 10:03 AM
> Subject: Re: [sdiy] LT1228
> 
> 
> > Am I crazy or blind but it seems as if National still produces the
> > LM13700. Is the LM13700 chip that bad?
> > http://www.national.com/pf/LM/LM13700.html
> >
> > //Gabbe
> >
> > Oakley Sound wrote:
> >
> >> Anyone used one of these? Its an OTA with output amp and its seems to
> >> still be available from Linear Tech. Its a bit pricey though and the
> >> offset spec is nothing to shout about. Might be worth a look though.
> >>
> >> http://www.linear.com/index.jsp
> >>
> >> Tony www.oakleysound.com Oakley Modular Systems
> >> Penrith, Cumbria, England
> >>
> 
> --
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> 

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