Mono/Poly (was: beating a dead DAC )

[Osamu Hoshuyama]

Hello, JH,

> Date:    Mon, 17 Jan 2000 01:33:59 +0100
> From:    "jhaible" <jhaible at debitel.net>
> 
> Hi Osamu, and list,
> 
> > The big (1W or 2W) resisters on SSM2033s are for heating the chips.
> > I've read an interview of the designer of Mono/Poly in a Japanese
> > book.
> >
> > Mono/Poly and Poly6 are the first V/Oct synths for KORG.
> > He said that they were used with the great stability of Hz/V VCOs and
> > was not satisfied with the stability of 2033 itself, so he added that
> > big resisters (heaters) to get sufficient stability.
> 
> This becomes even stranger now.
> 
> First of all, Poly6 and Mono/Poly had very different VCOs:

I'm very sorry.  My memory was wrong about poly6.
I remember that Poly6 has Korg-original PUT-based VCOs.

> The Mono/Poly, OTOH, used integrated VCO chips (SSM2033) which
> already had a heater *on chip*. It's too long for me since I last looked
> into a real Mono/Poly, so I can't be totally sure about these external
> resistors.


> When I built my MidiMini years ago, I used the Mono/Poly VCOs
> as a scheme to start with, but I've taken it from the schemos, so I might
> have missed the power resistor part. Maybe they placed an unregulated
> heat source (power resistor) next to the thermostated chips in order to
> decrease the temperature gradient from the chip to the ambience ? That's
> the only thing I could think of. It would reduce the 2033's power
> consumption,
> and in case it also improoved the regulation, it must have been very clever.
> But that's the first time I heard about that. Time to look into a real
> Mono/Poly
> again !

I checked the article again.  The designer said:

"In Mono/Poly, temparature is directry controlled by heaters
(resisters).  Surface temparature is about 65 degrees.  Other makers
were using thermisters but it is very difficult to stabilize.  Direct
temparature control is much easier and more stable, even though its
primitive.  Stabilization took 3 or 4 minutes."

I've never looked at Mono/Poly schematics.  But, I also have a real
Mono/Poly.  It has big resisters on/above VCO chips.  (Maybe the
resisters are temparature sensors.)

- -- ---- ----------- --- --- - ----- -- --- --- - - ------ - - - --
 Osamu HOSHUYAMA          Digital Signal Processing Technology Group
                    C&C Media Research Laboratories, NEC Corporation
               Email: houshu at ccm.CL.nec.co.jp,  Fax: +81-44-856-2232
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