[sdiy] Log/Lin VCAs/Transconductance amps

[Tom Wiltshire]

You're quite right, Louis. Although it is "previous generation", it  
is still around, so perhaps I should have put it on my first list.
I was wanting to emphasise the distinction between modern chips,  
which are all log, and older chips, which are all linear.

T.


On 11 Mar 2009, at 11:26, Louis van Dompselaar wrote:

> When did the LM13700 go out of production?  National still list the  
> LM13700 DIP16 as "full production".
>
> And it's available everywhere.  Futurlec even sell it close to the  
> National bulk price.
>
>
> Op 11 mrt 2009, om 12:14 heeft Tom Wiltshire het volgende geschreven:
>
>> There are a number of VCA chips still in current production and  
>> available:
>>
>> SSM2164 quad vca
>> SSM2018 single VCA
>> THAT2180/2181 single VCA
>> THAT2162 dual VCA
>>
>> All of these seem to be designed primarily for audio level  
>> control, and have a dB/mV control response (log). This contrasts  
>> with what I think of as the "previous generation" of chips for VCAs:
>>
>> CA3280
>> LM13700/13600
>> CA3080
>>
>> All of these basic transconductance amps have a linear response.  
>> Obviously there were a few SSM/CEM VCA chips around too (CEM 3360  
>> dual VCA for example) but these are in general even more expensive  
>> and harder to get than the short list above.
>>
>> Does anyone know of a cheap/easily available linear VCA or  
>> transconductance amp?
>>
>> Perhaps I'll have to linearize the SSM2164 and use it as a dual  
>> linear VCA instead. This provides an upper limit on cost, since  
>> the SSM2164 is about £4-5.
>
>
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