[sdiy] CMOS Synth

[Magnus Danielson]

From: "Osamu (Sam) HOSHUYAMA" <houshu at rogers.com>
Subject: [sdiy] CMOS Synth
Date: Sun, 02 Feb 2003 12:40:38 +0900

> Hello List,

Hi Osamu,

> Finally, my CMOS modular synth (MOSular ;-) began to work as a system!
> 
>     http://www5b.biglobe.ne.jp/~houshu/synth/MOSular01.JPG

Ah, finally someone done what I've proposed... a CMOS based synth!

Actually, there been precursors like the Pearl Syncussion. It's a mix of CMOS,
bipolar transistors and op-amps.

> Frankly, it's a toy project, but not so bad as a toy.  I know that 
> plastic lunch boxes can't last so long.

Possibly not the best ESD environment either... it's CMOS after all..

> However, they are extremely cheap (1 CDN each), and drilling and lettering
> panels are very easy. (Drilling a box took less than 1 hr.  I used 4 sheets
> of inkjet-printed paper for the panels.)  The boxes are not robust, but much 
> better than bare boards.  I think this is the best choice for my 
> limited tools and time in Canada.  I first planned wall-mount modular, 
> however, the panel is too weak to support so many plugs unfortunately.

Interesting solution never the less... ;O)

> Most of the schematics including block diagram are available here:
> 
>    http://www5b.biglobe.ne.jp/~houshu/synth/index.html

Interesting suite.

Hmm... do you have the GX1 service manual? I'd love to read it!

You should look for my conceptual idea of a 4069 based CV-ADSR. There's many
conceptual flaws in it, such as voltage range, but it is a cross-over of many
different use of 4069. I have this toy idea of how to build a synth with only
the 4069 as the active element (well, there's plenty of passive uses one could
dream up as well). The restriction to 4069s is a bit more obsessive, but it is
quite a bit of extra mind-bending which one needs at times...

>   * Power consumption is large because all the amplifiers (inverters)
>     are operated in class A.  (Heatsinks are needed for regulators.
>     I used 2 sets of 3 terminal regulators to distribute the heat, and
>     to reduce noise with VCF and soft sync with VCOs.)

Maybe you should run them at a lower voltage or use current limiting resistors
on the power-feeds, possibly with caps over the terminals.

>   * VCF and VCA are a little noisy and have some thump with fast attack.

And the balance-trimming didn't help you? Toss a sine on the CV input and
trim balance to minimize the signal on the output.

> Anyway, my absurd but challenging project has been almost completed.
> Thank you very much.

Thanks for sharing... I will be looking more at it ;O)

> My deepest sorrow to Columbia's accident.

Ain't we all, ain't we all?

Seems NASA got themself another issue with those boosters. Also, the congress
got themselfs to blame for half the safety testing staff being sacked and now
another 7 people dead. Great trade. Budget cuts and security rarely mix well.

Cheers,
Magnus