Archive of the former Yahoo!Groups mailing list: MOTM

Hi,

I've done a lot of layout work on the weekend, and the bigger part of the
Solina board is done.

Good News: As it looks now, it will all fit on one board, so the price for
the board will be under EUR 30.00 .

I think I have found a way to fit the 3 BBD lines close together without
much interference, by applying very strict EMC design rules: Each Delay Unit
(complete with clock oscillator, BBD and near-BBD filtering components) has
it's own GND plane, interconnections are very short and all done as
Microstrip lines.

Ok, I'll first have to try this on one prototype before I really know if it
works, and if it doesn't, I have to throw the concept over and start from
point zero, but that's my risk.

Your benefit will be that if it works, it will be ultra-compact, so you can
even think about retrofitting existing keyboards with whis. Or put it in a
very compact box.
All is relative, of course: We're still talking 160mm x 100mm here, which is
big compared to the average stomp box, but small compared to the interior of
a Solina keyboard's interior, and even small compared to the Boehm Phasing
Rotor 78.

The (hopefully slight) downside of this concept is that I'll probably ditch
the Dual-BBD "Roland Chorus" mode. I had intended to use the overhead of two
boards (instead of one) to be filled with the extra circuitry for this.
But I think with half tzhe size, and practically half the cost for the PCB,
that will be ok, will it?
A dual BBD chorus mode would fit on another of my planned projects better,
anyway: Adding a second (entirely optional) BBD to the CE-1 clone .

That's what's going thru my head right now.

I have to see how the remaining board space is eaten up, as I procedd
layouting. As I said, the complete extra control circuits for the "Roland"
mode won't fit in. But maybe the wonderful String-Sound-dedicated 3-band
Equalizer of the Crumar Performer will. (No promise, but likely.)

Ah, and the whole thing might run from 15V single supply, to make building a
PSU easier. (YOu can still connect it to a standard +/-15V modular synth
supply with the +15V unused - we only need the -15V.

And finally: I have verified the little quirks of the original Solina
modulation waveshapes, that make them differ from a simple superposition of
slow and fast 3-phase LFO sine waves. These will be reproduced in my
version, though by slightly different means, and partly adjustable.
Filters to band limit the signal to 12kHz (Solina) will be included, too.
(YOu can bypass this, though.)

If you're interested in such a board, please send me an email with subject
line "SOLINA - I'm interested"
This is by no means a binding order yet. :)
And, as I'll only sell the bare PCBs, you'll have to source the BBD chips
yourself: You'll need 3 (three) TDA1022 chips for this.
(The other components will be easy to get.)

All for now. Back to RIMU (my layout tool).

JH.

Now playing during PCB layout work:
Vangelis, Heaven and Hell
Jeff Johnson, Shadow Play
Jean-Michel Jarre, The Concerts in China