[sdiy] Problems with linearized SSI2164 ?

David G Dixon dixon at mail.ubc.ca
Thu Feb 7 01:36:14 CET 2019

> The SSI2164 has
> - higher control pin input resistance (10k vs 5k)

In the Irwin circuit, the control pin voltage is sourced from an opamp, so
this change in impedance should have absolutely no effect at all.

> - higher input headroom

It should still work exactly the same with the same input resistor (as long
as the feedback resistor on the output opamp is the same).

> - lower noise and distortion

This is just better specs.

> - larger gain cell transistors


> - etc..


> That lot together is a screaming "not drop in replacement" sign!

1) The only thing that has really changed from a end-user design standpoint
is the impedance of the control pin input, but the same control pin voltage
should still give the same gain, and if that voltage source is buffered,
this is a big fat nothingburger.

2) If the SSI2164 is NOT a drop in replacement for the SSM2164 (or it's true
drop-in replacement, the Coolaudio V2164), then I would submit that it is
the most facking useless IC in the history of ICs.  There are hundreds (if
not thousands) of designs using the 2164, and if these all have to be
changed, that's an enormous cost and a major headache for all involved.

I suspect that this thread alone will cost SSI a major chunk of business, at
least in the short term.  If it were me and I were reading this thread, I
wouldn't touch these shitty ICs with a ten-foot pole.  Good job SSI!

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