PLAN B analog blog

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@buzzclick-music.com> 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.
>