[sdiy] SSI2164

Tom Wiltshire tom at electricdruid.net
Wed Feb 14 01:01:14 CET 2018



> On 13 Feb 2018, at 22:17, Neil Johnson <neil.johnson71 at gmail.com> wrote:
> 
> Tom Wiltshire wrote:
>> 
>>> Neil Johnson wrote:
>>> 
>>> I can confirm that they are drop-in replacements, except in circuits
>>> where you rely on the control input resistance being 5k.  And you can
>>> drive the SSI with a much stronger signal.
>> 
>> While that’s all good, there are quite a few circuits that *do* rely on the control input resistance being 5K.
>> 
>> Still, it’s only mostly only a resistor tweak away from sorted, so not a big deal.
>> 
>> Are there any *improvements* over the SSM2164/V2164 that would lead me to prefer this new chip over the previous generation?
> 
> Several advantages come to mind:
> 1 - with a higher control port resistance the heating effect is
> reduced to a quarter of that with 5k, so Irwin linearised circuits can
> avoid the Hearn-style padding resistor on the op-amp output.
> 2 - you can drive the inputs at 4x what you can do to the SSM/V parts.
> 3 - built-in missing rail protection - saves a Schottky diode.
> 4 - distortion performance generally better than the original parts.
> 5 - other improvements I'm sure…

Sorry, I don’t understand what you mean by point (2).

Do you mean the signal inputs can be driven harder (more current)? I tried dropping the input resistors on SSM2164 to 15K (e.g. x2 the "standard” current) with no ill effects, but I never went as far as x4. I was trying to swamp offset cxurrewnts elsewhere in the circuit, and it worked to some extent, but was no massive improvement.

Or do you mean the CV input? What’s the advantage of that?

Not getting it, but maybe it’s late…

Thanks,
Tom




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