PLAN B analog blog

Yep!  And they're expensive as all hell. 


--- In PLAN_B_analog_blog@yahoogroups.com, "Norman Fay"
<vietgrove@...> wrote:
>
> So in effect, to offer lin/log response on board, you'd have had to
> double-up on the chip count for thos 2 cells?  And have some wasted
> capacity too.  Seems reasonable, thanks!
> 
> On Wed, Apr 23, 2008 at 1:13 AM, (i think you can figure that out)
> <peter@...> wrote:
> > A comment came up about the functionality of the Model 33 Tri/VCA.
> >  Why I kept the two of them at log only and the bottom unit the only
> >  one with a linear option.
> >
> >  The M33 uses the Analog Devices SSM2167 quad precision VCA chip as
> >  it's engine. This is one of the last surviving products from AD's
> >  acquisition of SSM and thank God the pro mixing industry embraced the
> >  part because it would be gone as well had they not been used in many
> >  high-end mixing desks over the last decade. The decision to go with
> >  the 2164 is a wise one as it assures better than .02% harmonic
distorion and a 120 dB dynamic range.   However, the basic nature of
these devices is non-linear.  To change that I incorporated Mike
Irwin's EDN published
> >  2164 linearization circuit and Phil Gallo's later addition to
this, also
> >  widely recognized  that incorporates the circuitry for
offset-free (read
> >  seamless) lin/log switching.  Both of these however require two
> >  segments of the 2167 to do their job - two of the four.  Knowing that
> >  half of the chip is taken by this single VCA, it leaves two others
> >  with Log response.
> >
>