[sdiy] Korg Poly61 a peculiar design!!

karl dalen dalenkarl at yahoo.se
Thu Apr 7 02:25:51 CEST 2011 

Nice but why not move the knobs ontop of panel print.

KD
--- Den tors 2011-04-07 skrev Doug Terrebonne <dougt55 at yahoo.com>:

> Från: Doug Terrebonne <dougt55 at yahoo.com>
> Ämne: Re: [sdiy] Korg Poly61 a peculiar design!!
> Till: "karl dalen" <dalenkarl at yahoo.se>, synth-diy at dropmix.xs4all.nl
> Datum: torsdag 7 april 2011 04:09
> I'm temped to do this to mine. Dump
> the digital control for pots - 
> 
> http://www.flickr.com/photos/37595587@N00/sets/72157622283778293/
> 
> Doug
> 
> 
> 
> ----- Original Message ----
> > From: karl dalen <dalenkarl at yahoo.se>
> > To: synth-diy at dropmix.xs4all.nl;
> Paul Cunningham <paul at cometway.com>
> > Sent: Wed, April 6, 2011 3:45:43 PM
> > Subject: Re: [sdiy] Korg Poly61 a peculiar design!!
> > 
> > Uses two 8049 micros, a major rebuild are needed new
> DAC+mux board.
> > Could be done but needs lots of work.More work then to
> build
> > new different from scratch. 
> > 
> > KD
> > --- Den tors 2011-04-07 skrev Paul Cunningham <paul at cometway.com>:
> > 
> > my Poly-61M suffered some severe battery damage,
> > > and i fear that my motherboard is toast. too many
> of the
> > > traces are corroded and as well as the pins of
> several
> > > resistors and the CPU... I've seen how some
> people fix this,
> > > and perhaps I'm just not up for it.
> > > 
> > > I would love to just replace the 1980s
> motherboard with an
> > > arduino or something similar. Does anyone know
> actually how
> > > dependent the synth board is on signals from the
> > > motherboard? I've seen some impressive Poly-61
> mods that
> > > basically add real-time control to several
> parameters, but
> > > some other oscillator signals are generated by
> the CPU?
> > > 
> > > The Poly-61 seems like an awesome sounding synth
> hobbled by
> > > a simple programming model. I'd love to augment
> it with 21st
> > > century software, or in the least a decent
> analog-based
> > > control system.
> > > 
> > > I think I have the schematics somewhere, but I
> struggled a
> > > little bit to understand how all the circuits
> were related.
> > > Is this what's in the service manual PDF? I'll
> have to
> > > figure out what I have...
> > > 
> > > i'd love to find a working replacement KLM-509A
> board if
> > > anyone knows where to find one. -pc
> > > 
> > > 
> > > On Apr 6, 2011, at 6:02 PM, Dan Snazelle wrote:
> > > 
> > > > I actually like the sound of the poly61 for
> > > SOMEthings!!!
> > > > 
> > > > 
> > > > 
> > > > 
> > > > Sent from my iPhone
> > > > 
> > > > On Apr 6, 2011, at 5:46 AM, Tom Wiltshire
> <tom at electricdruid.net>
> > > wrote:
> > > > 
> > > >> Have you got a link to some decent
> schematics for
> > > the Poly 61, Karl?
> > > >> 
> > > >> I've got a service manual PDF for it,
> but it's
> > > more-or-less unreadable.
> > > >> 
> > > >> Thanks,
> > > >> Tom
> > > >> 
> > > >> On 6 Apr 2011, at 01:44, karl dalen
> wrote:
> > > >> 
> > > >>> VCF:
> > > >>> 12db LP LM13600 using a MS20 VCA
> with limiting
> > > diodes in resonance
> > > >>> feedback but before VCA also the
> feedback not
> > > only goes to the input
> > > >>> of the filter but to first cap like
> half way
> > > S/K and no local OTA
> > > >>> gain loops but one fixed over both.
> > > >>> 
> > > >>> I have checked trough all other
> analog Korg
> > > products and this VCF
> > > >>> are unique to the P61.It should have
> a
> > > peculiar Bw hump because of
> > > >>> this.
> > > >>> 
> > > >>> VCA:
> > > >>> MS20 final VCA. One SSM2056 EG split
> use VCA
> > > and VCF.
> > > >>> 
> > > >>> DCO1:
> > > >>> It's a complete saw VCO core, a
> regular Op amp
> > > integrator/comparator
> > > >>> design. The ramp reset comparator
> also feeds
> > > another comparator that
> > > >>> sends this signal back to *both* 1/3
> of DCO1
> > > and DCO2 8253 timers gate
> > > >>> input, then one of the 8253 timers
> sends a
> > > pulse back to the integrator
> > > >>> NPN ramp reset transistor in the
> VCO!! Odd!
> > > >>> 
> > > >>> Could this perhaps mean that half of
> timers
> > > are actually used to measure
> > > >>> the frequency of the VCO and if
> wrong in
> > > realtime restart it on a per
> > > >>> cycle basis?! It could work if the
> value are
> > > compared to a predefined
> > > >>> LUT. Or is it just a bogus thing to
> distract
> > > anyone viewing the schematic?
> > > >>> 
> > > >>> The output of the ramp integrator
> are sent to
> > > a comparator to create
> > > >>> PW wave.
> > > >>> 
> > > >>> DCO2:
> > > >>> DCO2 are made out of 1/3 8253
> driving a 4520
> > > divider who's output's
> > > >>> are selected by a switches and
> summed by a
> > > weighted resistor net
> > > >>> acting like a DAC to create saw. A
> redundant
> > > signal goes to divider
> > > >>> reset to actually turn off the
> chip..
> > > >>> 
> > > >>> Apparently resolution of wave are
> likely
> > > dependent of octave selected
> > > >>> otherwise only one switch would be
> needed.
> > > >>> 
> > > >>> VCO ramp integrator note CV are a
> 7bit R2R
> > > generated by the same CPU
> > > >>> that scan's KBD that then feed a
> common expo
> > > who are muxed out to
> > > >>> each VCO. (Polysix/Trident)
> > > >>> 
> > > >>> The driver for the timer DCO's are a
> VC RF
> > > multi vibrator who in turn
> > > >>> are driven by bend and vib voltages,
> the CLK
> > > signal are then driven
> > > >>> into a prog divider to create
> semitone offsets
> > > for DCO2, finer detuning
> > > >>> presumably by 8253 timer itself.
> > > >>> 
> > > >>> There are no regular muxed DAC for
> the
> > > parameter CV's instead each
> > > >>> has its own DAC trough a bag of 8255
> driving a
> > > even larger bag of
> > > >>> weighted resistor net's.
> > > >>> 
> > > >>> DAC for Cf of VCF are only 6 bits.
> However
> > > PWM, VCF, Vibrato modulations
> > > >>> are full resolution from the analog
> triangle
> > > MG.
> > > >>> 
> > > >>> In other words an awful sounding
> poly but a
> > > great, peculiar and funny
> > > >>> VCO/DCO design.
> > > >>> 
> > > >>> Disclaimer: I might be utterly wrong
> in all
> > > that said here.
> > > >>> 
> > > >>> Thanks for your
> attention....G'day...
> > > >>> 
> > > >>> KD
> > > >>>
> > > _______________________________________________
> > > >>> Synth-diy mailing list
> > > >>> Synth-diy at dropmix.xs4all.nl
> > > >>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> > > >> 
> > > >>
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> > > > 
> > > >
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