[sdiy] Keio TS201012

[Colin f]

> From: Romeo Fahl [mailto:rfahl at pdx.edu] 
> Sent: 26 February 2006 23:24
> To: Colin f
> Cc: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] Keio TS201012
> 
> Thank you for that bit of info.  I was wondering about that just last 
> week.  How did you manage to find that out?

I had a visit from Tony Allgood a couple of weeks back, and when we were
discussing the miniKorg, he mentioned he'd been able to just pop the lid off
one of the Keio ICs and see what was inside.
It turned out this was just the case with the oscillator IC, not the filter
IC, but when I opened a filter IC and found it was potted, I noticed that
the potting material was quite soft.
An hour with a scalpel later, I had exposed the circuit.
I've thrown a quick page about it together here:
http://www.colinfraser.com/m700/index.htm


> From: owner-synth-diy at dropmix.xs4all.nl On Behalf Of Aaron 
> Lanterman
> Sent: 27 February 2006 07:43
> Subject: Re: [sdiy] Keio TS201012

> Is this the same circuit topology as the Yamaha GX-1 filter?

I'm not sure about the specifics, but AFAIK the GX-1 is a diode ring based
Sallen & Key filter pair too, so they must be pretty close.
By coincidence, I had a play with a GX-1 last week, and the filters did
sound very miniKorg like to my ears, especially when tweaking them with the
programmer.
An impressive piece of kit, that was...

Cheers,
Colin f