Re: Re: [sdiy] THAT 2181C VCA\'s

[Roman]

I just looked at THAT2181 datasheet and I must
say it's better suited for synth building than SSM2164.
In THAT you have access straight into expo pair, while
SSM adds 5k internal resistor, creating high voltages
for the tempco  - 200mV/oct. Also controll feedthru
rejection is about 60dB in SSM and over 100dB in THAT.
THAT also has specified wider control range and bipolar
control inputs (more choices).
And it comes in 8-pin package, so you don't have to
waste 3 VCAs if you want just single VCO made with THAT.
The only thing common to both is 3300ppm control tempco,
but with THAT you can use the same tempco technique as
used in most of discrete expos.

And I don't get any money form THAT company for saying this

Roman


---- Wiadomość Oryginalna ----
Od: Steve Allen <snd_audio at yahoo.com>
Do: Craig Critchley <craigc at nwlink.com>,WeAreAs1 at aol.com,synth-diy at dropmix.xs4all.nl
Data: Mon, 3 Nov 2003 22:26:19 -0800 (PST)
Temat: Re: [sdiy] THAT 2181C VCA's

>Thanks Craig,
> I checked Romans site, and it looks like I'll be
>spendin the weekend breadboardin and solderin : )
> YES!!!!
> Oh yea, and Thanks Roman and all those who sent a
>reply.
>This list ROCKS!!!
>--- Craig Critchley <craigc at nwlink.com> wrote:
>> You can linearize a VCA response by putting a second
>> VCA in feedback loop -
>> EDN has a short article on doing this with the
>> SSM2164 which also has
>> exponential response. Tracking is very good,
>> especially if you use two VCAs
>> on a single chip, but of course you double the
>> number of VCAs you need.
>> 
>> The article may be found here:
>> 
>>
>http://www.reed-electronics.com/ednmag/index.asp?layout=article&articleid=CA233728&rid=0&rme=0&cfd=1
>> 
>> For VCFs and VCOs, having an exponential response
>> might get rid of needing
>> an external expo converter, but you'll still have
>> the temperature
>> coefficient to deal with (at least, that's what it
>> looked like with the
>> 2164.) I'm not sure how good the log conformance is,
>> I haven't tried myself.
>> 
>> Roman Sowa's site has VCFs and VCOs built with the
>> SSM2164 here:
>>