[sdiy] Re: Walsh Generator Release!!!

[Tony Allgood]

Hi all,

Just back off holidays and a bit late in replying to all this one:

> http://www.oakleysound.com/walsh.htm
> Tony, show them some pictures...

I'll get some photos done of my now half complete unit. Its still only
on boards, so no nice case for it yet. The circuit did reside on four
veroboards. Each around 40 x 12 cm in size.

The biggest section of the circuitry is the VC mixing, which had its own
board. The second biggest bit was the Filtering (actually the prototype
SuperLadder) and the two VC-envelope generators. This board has now been
trashed for parts sciving. The Walsh bank itself is fairly small, taking
only a third of one of the boards.

You also need a high frequency VCO to drive the thing. With 31
components, you are going to need a 64 times fundamental. 64 is required
because you absolutely need a square wave driver to generate the series.
I used a LM13600 based triangle VCO with reasonable success so long as
you limit your top note to 4KHz or so. I did think about some sort of
clever 'range switching' that switched off walsh components over 20KHz,
therfore removing the need for such a high VCO at high fundamentals.
However, this feature would not allow smooth FM for modular use, and was
too time consuming to implement for what was basically a fact finding
experiment.

The final board was a set of 31 sliders. The 1 walsh coeffient is only
DC so was omitted. And no its not in any way intuitive to use. But then
practice makes perfect. I guess the first Moog modular was a bit
daunting as well, to say nothing about the DX-7.

Regards,

Tony Allgood                       Penrith, Cumbria, England

Oakley Sound Systems                     www.oakleysound.com
Modular projects            www.oakleysound.com/projects.htm