[sdiy] Expo in one chip?

Mattias Rickardsson mr at analogue.org
Fri Jan 5 18:33:36 CET 2018


On 5 January 2018 at 18:16, Neil Johnson <neil.johnson71 at gmail.com> wrote:

> Mattias Rickardsson wrote:
> > Also, the RC value of the compensation network needs to be changed a
> little
> > bit if you use input resistances far from the typical values, so it
> might be
> > good to have them outside after all.
> Indeed.  I asked SSI if they could provide some notes or equations in
> the datasheet to use to work out compensator component values for
> different input resistors.

Great! Let's hope they find some good recommendations. :-)

> Actually they are a tiny bit noisier (about 1/2 to 1 dB from the data I've
> > seen so far) than the V2164, but a tiny bit lower noise (again about 1/2
> to
> > 1 dB) than the original SSM2164 if you swap them in the same circuit. But
> > the reduced distortion can allow for a lower-noise circuit design for a
> > given task.
> The datasets that SSI have collected show that overall the SSI2164 is
> quieter than the SSM2164 in class AB mode, but a little bit noisier in
> class A mode, and in both modes with much reduced distortion.  Overall
> I think it's an improvement, and it looks like the spread is tighter
> for the SSI part (or they chose some really good SSI parts and some
> really bad SSM parts...).

The spread seems tighter, yes... And when it comes to Class A my experience
is that the chip becomes way too noisy - it's already in Class AB the
noisiest part of a typical modern synth voice.

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