[sdiy] moog module survey

[Kevin Lightner]

>Hey Kevin,
>
>Are you and I the only ones around lately? Most of the information I've
>got, I've got from your site or the SOS site.

I think most of the folks here have more experience with building 
their own designs than working with original Moogs on an ongoing 
basis. We're all specialists and this is one of my specialities. :)

I'm not one to lend much to a thread that asks which atmel processor 
has the most ports, etc.  ;-)

>
>Exactly. This is why the other post on the LM308. The 923 uses two
>LM308s in the filters,  with different compensation capacitors. This
>means I have to find a LM308 and see what the different caps do to the
>response.

Are 308's that hard to find?
I have about 15 in DIP and 5 or so in TO-5 cans here.

>
>I started with the 923 because the network to create the pink noise
>intrigued me. I can't imagine trying to come up with that combination in
>the early sixties. I'm not sure I would do it even now with my
>spreadsheet that I use to design filters. There are five different
>filters - and they all work by loading the signal that feeds the output
>buffer. The circuit is just begging me to build it. And, I know I don't
>have exact matches for the capacitor values in my bins. I stock 1, 2.2,
>4.7 as my standard caps.

The values in the pink noise filter are all available.
(Should I sell you a kit? ;-)
The 32 mfd caps decoupling the outputs can be "assembled" from two 
separate caps if you want to be that precise. The 2.5 mfd as well. I 
know there's some loading after them, so you may well want to be 
precise.


>I'm temped to sort some resistors to find the exact values and order
>some caps.

Common here. I'm nuts enough to match holco 0.1% resistors in some cases.

>
>Another problem with the 923 is finding something to replace the SD10
>noise diode. I'm probably going to go with a zener.

That *is* a zener in the circuit.
If I could recommend, buy several zeners and do listening tests.
There can be a huge variance in their spectrums and this is probably 
more important than getting the caps perfect in the filter(s.)


>902
>I was going to start with the schematic from the moog modular service
>manual on your web site. Do you have schematics for all 5 versions?

No. They're very similar, with small changes.
The early ones don't have the same bridge rectifier clamping found in 
the outputs and some other goodies.

>
>I suspect there are at least two different versions of the white noise
>generator, before the pink noise was added to create the -A version. The
>schematic drawing appears to have some changes to the power supply
>filtering.

It's really hard to say just how many variants there are of the modules.
They made small changes in mid-production all of the time.

>
>The SOS article on moog modulars states that the 902 has a punch useful
>for bass that hasn't been equalied by anything else. And that statment
>was the source for the idea of taking a survey to see what people think.
>After all crtics aren't always right.

Again subjective. :)
The Moog does have an expo/lin switch and the expo setting can be 
used for some nice percussive curves, but the one thing I've learned 
after playing with synths so much is not to trust what people write 
about for the most part. There's a ton of false rumors out there and 
money changes hands everyday over expectations, disappointments, 
fear, etc.

-- 
Regards,
Kevin Lightner

Myself: http://www.synthfool.com
Service and sales: http://www.moogmusic.com/service.php
Sales: http://www.cluboftheknobs.com