[sdiy] M108 and the Curse of the Silent Jen

[Neil Johnson]

All,

Audience Warning: if you think the Jen SX1000 is a weedy, crappy little
synth with no value whatsoever, stop reading now, this email will only
annoy you.


       ...


Ok, on with the topic.  I've been looking at repairing a Jen SX1000 which
has a dead M110 organ chip (it does both keyboard scanning and pitch
generation combined).  Sadly, these days M110's are as rare as hens teeth,
so I've had no luck finding a replacement :-(

Enter the M108.  It is a close cousin to the M110, sharing the same
keyboard scanning circuitry as the M110 (and indeed can be run in parallel
with it, such is found in the Siel Cruise).  It has polyphony as its main
advantage, but it lacks the exponential current output, so I'd wave
goodbye to the sawtooth and filter keyboard tracking.  Being as there's
only one analogue signal path, I'm not sure how much gain the polyphony
really gives.

So, the conclusion I am rapidly coming to is to design a complete
replacement for the M110, something like the Kenton retrofit card (now no
longer available), with MIDI In (and perhaps MIDI Out too, limited to
NoteOn/NoteOff), CV/Gate out, etc etc.  Probably based on an Atmel AVR for
those that are interested in such matters.

Heck, I might even put an arpeggiator in for good measure :-)

Also, I think it would be better to save the remaining M108's in the world
for machines that originally used them, rather than find a new need for
these rare chips.

<sales pitch>

Consequently, I have three M108's now going spare: one NOS still in
original anti-static packaging, and two used but believed to be working.
Given the current value these things go for, I'll let them go for 20 UK
pounds for the NOS one, and 12 UK pounds each for the used ones.  Buyer
pays packaging, etc.

</sales pitch>

There are data sheets for all these devices on my website in the data
library.  I thought I'd give this list first chance on them, before adding
them to the website.


      ...


So, time once more when we synth-nuts gather round a hot soldering iron,
join hands across the globe, and reflect on the joys and sadness, the
triumphs and failures, of the year gone by.  And a chance to look towards
the future with hope.  Turn your web browser now to the Synth Builders
Prayer:

	http://www.njohnson.co.uk/synprayer.html

May your solder flow freely and your VCOs not soft-sync through the power
supply rails.

Wishing you all a Wonderful and Tuneful New Year!

Neil

--
Neil Johnson :: Computer Laboratory :: University of Cambridge ::
http://www.njohnson.co.uk          http://www.cl.cam.ac.uk/~nej22
----  IEE Cambridge Branch: http://www.iee-cambridge.org.uk  ----