PLAN B analog blog

Due to many requests, the Model 23 ASR is back on the front burner, with changes.

Please hear me out before you scream.

It's no longer dual.

Relax - we'll be selling them at a 10% wen you buy two.

Reasons:  In order to provide the type of accuracy which you would want, the key 
components had to undergo a serious upgrade.  The upsdies to this are many:

One, the M23 is now 4HP wide instead of 8.  Secondly and most important, design 
improvements from the original prototype will now faithfully pass a keyboard signal with 
less than 1mV (1 cent)  variation from tap to tap.  Third, you'll now pay less for what the 
dual was going to sell for originally.

I've decided to incoporate the mother of all S+H chips, the Analog Devices SMP04. Four S
+H circuits, laser trimmed on a single monolythic chip, each with it'sown precision laser 
trimmed timing cap assure what you get out of one will accurately be passed to the others.   
Add to that the Analog Devices AG212 precision quad switch (three of them!) which assure 
the accuracy of the  S+H's are passed to the outputs. 

I would imagine there would be nothing more useless than playing a keyboard through the 
M23 and having each output detune itself randomly from tap to tap. You would think there 
would be a work around, like intentionally detuning the VCOs to compensate.  This will do 
the trick within a cetain voltage range, but there's also the matter of linearity that the AD 
chips address and detuning does not.  

The only problem I was seeing was the added cost of these chips bringing the cost of a 
dual unit too high for many.  I want people to use ASRs, they're fun.  So I redesigned as a 
single to help that along.

An internal flat cable will allow for mutliple M23's to be stacked in series for 6, 9, 12, 15, 
18, etc. stage shift registers.  To make that a bit more feasible, we will be offering a 10%
discount when purchased in pairs.

Go here for more details and a faceplate rendering:

http://www.ear-group.net/model_23.html

The M23 will be out soon.

-P