[sdiy] THAT ICs and SSM chips

[Seb Francis]

Ian Smith wrote:
> Hi all,
>
> Just a quick question about THAT Corp. ICs, specifically the 2180 VCA chip; and the SSM range of chips...
>
> ok, a couple questions...
>
> How do you guys feel about these modules in a chip? How do they compare to a module made out of discrete components?
>
> And the second question... where can you get SSM chips these days?
>   

Hi Ian,

Modern one-chip VCAs such as THAT2180 or SSM2018T are excellent and you 
will find it hard to get close to their performance with discrete 
circuitry.  These are both pre-trimmed versions - at the expenses of 
some extra components you may get slightly better performance using 
externally trimmed versions THAT2181 or SSM2018.

If quality is not so important for you (e.g. you are just building a VCA 
for an analog modular synth, rather than something that must treat a 
full audio signal with absolute precision) then you could also look at 
the SSM2164.

The best solution will depend on your application.  Simple discrete VCAs 
will impart more 'character' such as CV feed-through, distortion, etc. 
which may be desirable in a synth application.

Regarding your 2nd question: most SSM chips are obsolete (expensive & 
difficult to obtain).  But I assume from your question you are talking 
about the modern SSM VCA ICs which are made by Analog Devices and can be 
obtained easily, including from AD themselves.

Seb