[sdiy] SIP filter modules coming

Tom Wiltshire tom at electricdruid.net
Wed Apr 25 18:36:08 CEST 2018

> On 25 Apr 2018, at 16:29, KD KD <pic24hj at gmail.com> wrote:
>> Tom
>> Alfa have got all kinds of good stuff in the pipeline, from what they told me:
>> a quad OTA based on the 13700 (but without the stupid buffers) called the
>> AS13704, and a modern clone of the CA3280, AS3280. Also a AS3394E
>> described as an “Extended” CEM3394. Sounds very interesting.
> The 13600 buffers is not stupid, just what they bothered to do back
> in the day for what was required on the request from el-organ
> manufacturers apparently.

Yeah, ok. Maybe “stupid” is a bit strong. But I’d much rather have had an op-amp there instead, even if it was only a 741-type thing. Then you could have done a unity-gain follower for your OTA Cap-to-ground style filters, or an inverting integrator, and you’d also be able to implement a proper I-to-V stage for VCA applications, which gives a much better result than a resistor to ground followed by the buffer.

Anyway, I can see why Alfa left them off. Many, or even “most”, designs with the 13600/13700 seem to leave them out. I only really see them used in stompbox circuits where minimal parts seems to be a more important design objective then overall quality.


       Electric Druid
Synth & Stompbox DIY

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