[sdiy] Inside a Roland Dimension-D or schematics?

[jhaible at t-online.de]

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>Absender: xinclxsynth-diy at mkv.mh.se
>Betreff: [sdiy] Inside a Roland Dimension-D or schematics?
>Empfänger: synth-diy at node12b53.a2000.nl



> Does anyone know what's inside a Roland Dimension-D? Schematics would 
be great!

Coincidence ?  I'm just in the process of building a clone.
I wanted to wait until it's finished, but now that you ask ...

I plan to finish it first (need a frontpanel etc.) and then
make a clean drawing of my (modified) schemos to publish 
them. Expect it in a few weeks. (Roland sells the original schemos).

The original uses two obsolete 1024-stage Panasonic BBD-chips.
I replaced them with four 512-stage TDA 1022's (out of production,
too, but still available). Results are very promising so far.

The best chorus I ever heard - actually the only chorus I would
use for 2-VCO-synths. It's so *subtle*, rather than spectacular.
(Most chorus units produce "spacy-ness" and artificial "width" -
this one just enhances the signal without much side effects.)

The secret of the Dimension D, as I see it, is a very clever
equalizing of the various signal paths. 
It has two independend delay lines (true stereo). Delayed
signal is mixed in to the stereo channel it was derived from,
and also cross-mixed to the other channel with opposite polarity. 
Normally this would result in a loss of lower frequencies, but the 
cross-mixing is filtered with a low-cut (HPF, and the direct signal is slightly 
bass-boosted. Similar stuff is going on in the upper range.
Result is that the overall brightness and bassy-ness is almost
not changed when FX is switched on or off. 

> Is it a very slow chorus, fixed phase-shifter or what?

Slow chorus (I think 0.5 Hz and 0.25 Hz) with rather long
delay times, and that terriffic filter / cross-mix matrix.

JH.