[sdiy] SIP filter modules coming

[Quincas Moreira]

In a decade or two you´ll be able to print any historic chip at home :)

On Fri, May 11, 2018 at 6:53 PM, Tom Wiltshire <tom at electricdruid.net>
wrote:

>
> > On 12 May 2018, at 00:40, KD KD <pic24hj at gmail.com> wrote:
> >
> >> 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.Tom!
> >
> > A FET tranny will do wonders, anyhow of-course i concur it would be nice
> to have
> > proper buffer but if you look into the SDIY archive you will find when
> > Harry Bizzell
> > sorted out the difference between 13600 and 13700 buffers and why.
> >
> > What we wanted is the 13600 buffers high beta auto bias but without CV
> > shift poping but instead we got low beta 13700 buffers.
> >
> > You have to go way back in time to see lots of buffer usages but thats
> > with 13600.
>
> Totally agree about the FET buffer. There are several classic Roland
> filter designs done this way; 13700 Ota with FET buffer. In some ways this
> combination is what “the Roland sound” means to me.
>
> Tom
>
>
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-- 
Quincas Moreira
Test Pilot at VBrazil Modular
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