[sdiy] SEM filter questions

[Magnus Danielson]

On 04/22/2012 10:15 AM, Neil Johnson wrote:
> Magnus Danielson wrote:
>>> Nah. While Oberheim did use some CEM and/or SSM chips for things like
>>> ADSRs and so on the filters were 2-pole SVFs based on CA3080s.
>>
>> Oh really? For what synth are you talking about? It really changes over
>> the years.
>
> I was focussed on SEMs. It may well be that later OBs used more esoteric
> chips.
>
>> SEMs use really standard stuff. The CA3080 is as special as it gets.
>
> I did look at an OB-X a few years ago, and I'm pretty sure that had
> similar 3080-based filters.

It's really very similar when you put the schematics next to each other. 
The quick explanation for the OB-X is that it is essentially the SEM x4 
or x4 and adapted to the polysynt world, in particular the envelope 
generators is replaced.

>> OB-X is really SEM like filters, but when you get to OB-8 it is all
>> modernized.
>
> I couldn't possibly say, having neither owned an OB-8 nor looked at its
> schematics.

I have for some reason 2xSEM, OB-X, OB-Xa, OB-8 and Xpander.

Cheers,
Magnus