[sdiy] DIY Polysynths

thx1138 thx1138 at earthlink.net
Tue Jul 28 18:40:38 CEST 2009

On 7/28/09 6:15 AM, "GEORGE HEARN" <georgehearn at btinternet.com> wrote:

> Guys, I think we all need to get away from using CEM's.  With modern SMT there
> is really no excuse for it in DIY projects anymore.  Think of all those
> prophets, jupiters, memorymoogs etc. that will die because a bunch of CEMs are
> rotting on some breadboard in a half finished project in a  shed somewhere!
> I put my hands up and admit to using a few myself, and I put an SSM2040 in
> upside down once too.. though i've made a lot of effor to circumvent the need
> for 'em..
> Finally I've started putting some stuff on the web at www.hearnmorley.com
> George
> --- On Tue, 28/7/09, Florian Anwander <fanwander at mnet-online.de> wrote:
>> From: Florian Anwander <fanwander at mnet-online.de>
>> Subject: Re: [sdiy] DIY Polysynths
>> To: "synthdiy" <Synth-diy at synth-diy.org>
>> Date: Tuesday, 28 July, 2009, 12:08 PM
>> Hello Tom
>>> these below. Can anyone add anyone else to this list?
>> It is not yet publishable, but sometimes I am continuing to
>> work on a
>> four voice expansion for my Korg Monopoly.
>> Also it won't be completely diy, because I will start with
>> a readymade
>> CEM-based prototype of a Doepfer A-135-2 (a not yet
>> released product
>> http://www.doepfer.de/a1352.htm).
>> The idea is to pick the CV, Gate and  VCO-Signal from
>> the Monopoly and
>> to handle it outside in a additional four voices. Each
>> voice will
>> consist of one VCO (CEM3340), VCF, VCA (CEM3372) and two
>> Tom-Wiltshire-envelopes. No additional LFO at the moment.
>> The most complex and time consuming task shall be the
>> control panel,
>> which will provide access to the four individual voices in
>> three
>> different modes:
>> 1.) one set of controls determines the sound of all four
>> voices
>> 3.) each voice is controlled by its own set of
>> potentiometers/switches
>> 2.) one set of controls determines the sound of all four
>> voices, but the
>> other potentiometer sets should provide offsets from these
>> master values.
>> Until now exists the breakout from the Monopoly, one voice
>> on a soldered
>> breadboard with the VCO and two of your envelopes (plus the
>> existing
>> VCF/VCA module). It basically works, but now I am lacking
>> much time to
>> complete it (and also there are always those small (and
>> bigger)
>> modification ideas and repair jobs, that crop up every now
>> and then.
>> Florian
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Hello George,

I agree with your comments on the cessation of using older SSM/CEM chips for

What we need is to go back to the age of invention when op-amps,
transistors, OTA's were the building blocks of new projects. True innovation
again vs re-hashing already existing products.

Several times Bernie Hutchins and I discussed this as the true path of
audio. What makes certain transistors sound better than others? How to
thermally stabilize Filters, oscillators, Clocks etc.

What about the re-introduction of Vacumn tubes into analog designs. Guitar
players still prefer the sound over solid state argument.

What about keyboard innovation and alternative controllers? I am a wind
player and would love to have a Lyricon type of controller again for my
synth. I prefer to use a non keyboard controller but there again I am
interested in Time of Flight methods for keyboard design.

During my Career I have worked for PPG, E-Mu, Oberheim building the products
of these companies and I was always amazed on how little imagination existed
in some of these products.

This is one reason I went into Motorola over 24 years now. The time to go
back to the transistor now calls me again. I have been building DSP5600x and
DSP563xx, and DSP5672x based products for home Theatre, Car Audioand Pro
Audio products. I am sure many of you have used one of my DSP's in some form
or another.

Another poorly understood/executed product was the pitch to voltage
convertor. Gentle Electric had a unit , (which I still have) that worked
pretty well on Flute. Start playing overtones and the tracking gat a bit
weird. Guitar products such as the 360 Systems Slave Driver was a bit
similar in nature. Clean fingering on the fret was required or the tracking
lost it's mind.

Several people from this email chain and I have been discussing DSP's, ARM,
Coldfire and synthesis. I hope to be able to help where I can but I prefer
to innovate new projects rather than just dredge up the Prophet 5 or Korg
Poly6 type of projects. Still I look for feed back and a sense of direction
from this Synth-DIY forum. Perhaps I expect too much too soon, but I think
we all look to be origional at some point.

With best regards,

Terry Shultz
Freescale Semiconductor Inc.
DSP, ARM Audio Technology

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