[motm] Re: [sdiy] Frequency Shifter FS-1A update

Andre Majorel aym-htnys at teaser.fr
Sun Feb 24 18:51:15 CET 2008


On 2008-02-04 20:00 +0100, JH. wrote:

> >Thanks for the update. On board 1, Q2 and Q3 are either 2 x 2SA733
> >or 1 x 2SA1349. Neither seem easy to find.
> 
> You don't have to take that 2SA733 verbally. And decent pnp
> transistor with the right pinout will do.
> No matched pair required. There is a trimpot to adjust the
> balance between the two expo outputs, because some of the OTA
> chips I tried had terrible matching. That trimpot will even out
> any transistor mismatch, too.

Thanks. Something else : I was wondering how hard it would be to
put N sets of boards behind the same panel for an N-voice
frequency shifter module.

The mic stuff could be left out.

The RANGE, TUNE, MANUAL and FINE pots are just voltage sources so
they could be shared.

The LIN FM pot would have to go or be replaced by N VCAs.

Replace the EXP FM pot and NORMAL/INVERT switch by a +/- voltage
source controlling N four-quadrant multipliers.

Make the NORMAL/DEEP PHASE switch an NPDT.

Replace the whole output dry/wet and feedback part by some
combination of VCAs and NPDT switches. Or, since it's for a
modular, provide just one N-way input (AUX), two N-way outputs
(SUM and DIFF) and do everything else with external mixers and
VCAs.

Did I miss something ? (Other than the fact that it's an utterly
crazy idea.)

-- 
André Majorel <URL:http://www.teaser.fr/~amajorel/>
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