ah, thanks for explaining Dieter, once again i am foiled by pesky physics!
looks like you'll sell me some of the quad lfo / vco modules then!
there's always a silver lining!

thanks,

Will.



To: Doepfer_a100@yahoogroups.comFrom : yahoo@... : Wed, 29 Oct 2008 14:48:32 +0100Subject: AW: 1 Let me hear your bright new ideas for future Doepfer A100 modules!

> hello,>> i'm sure this is achievable with existing modules, if it is could> someone explain how (four phase shifters ), but the other day I> decided that I could do with a module in which you can input a> waveform audio or cv and have seperate outputs in 90 deg/180/270> deg etc phases.like the quadrature modules which exist but from> an input rather than internal occillators.> a quad-phase shifter i suppose using four seperate phase> shifters-would you be able to set them accurately enough > diy'ers-would this be simple enough to knock up i'm no engineer> but i can solder things together ok. sounds simple to me....but> then lots of things do that aren't. :(A 90 degree phase shift over a wide frequency range is not easy to realizebecause the phase shift of a normal phase shifter is not constant over thefrequency but depends upon the frequency! It's the function of the domefilters in the (obsolete) A-126 frequency shifter. In the A-126 we used a12-stage allpass filter to approximate a 90 degrees phase shift in thefrequency range 6 Hz ... 12 kHz with +/-2 degrees error. It's very difficultto adjust a dome filter as the phase shift of each all pass affects theothers too. It took more than 30 minutes to adjust the dome filter of theA-126.180 and 270 degrees can be achieved by intverting the signal (180) or the 90degree signal (270).Best wishesDieter Doepfer

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