AW: Analog rack backplane idea?

[Magnus Danielson]

>>>>> "HJ" == Haible Juergen <Juergen.Haible at nbgm.siemens.de> writes:

 >> However such a system would involve quite a dedicated design
 HJ> phase, from
 >> backplane pinouts to sheet metal to edge connectors on the circuit
 >> board. I mean, I could do it, but I don't see the effort being
 HJ> justified
 >> by the demand. It would just be nice to see somebody do it....

 HJ> Graham Hinton once built as System for himself where he could
 HJ> change modules on the fly.

 HJ> Not a bad idea indeed, because you might want to have 10 different
 HJ> VCFs to choose from, but rarely use more than 3 in one patch.

Hmm... this is very true.

I have been considering building a crossbar based switching system for
analog signals so that I can route the signals and controls this way.
The crossbar switches is available for a fair price at 16X8 and seems
to have a good enougth separation and quality. Buffering the signals
will certainly help things up. In such a system you could have the
rack full of cards and have the controls at a separate place.
There is other aspects of such a system. I have considered doing this
to my 4 ASM-1 cards.

One can build quite large systems with good or none route blocking
properties.

 HJ> A standard backplane designed for digital signals might have too
 HJ> much crosstalk for analogue signals, I guess.

As things get up to frequency in the digital world will the analog
problems like crosstalk become more problematic. Even if the crosstalk
levels that is accepted at 100 MHz and above is not really acceptable
to music will the solutions in many case have fairly good properties
in those low frequencies that we use in synths mostly...

The shielding practices, impedance matching and all that is a good
thing most of the time for most signals. In RF you can't cut the
corners as easy as you can do in near DC (thus the audio range).

When you find a large 2.6 GHz overshot ringing on the output of a laser
module for a 1 GHz clockrate digital signal you get quite aware of the
facts that I am talking about ;)

Cheers,
Magnus