Exciter

[David Halliday (Volt Computer)]

I went to the IBM Patent server ( http://www.patents.ibm.com/ibm.html );
put "Aphex" in the search line and come up with the following 13 citations:

Functional control block for voltage regulator with dual servo loops
Concentric servo voltage regulator utilizing an inner servo loop and an
outer servo loop 
Wave dependent compressor
Peak accelerated compressor
Reflected plate amplifier
Transient discriminate harmonics generator
Frequency discriminate leveler
Audio bass frequency enhancement
Logic enhanced noise gate
Discrete parallel path modulation multiplexer
High frequency expander device
Impulse detection circuit
Split-band clipper 


All of these patents are available for viewing on this web site.





-----Original Message-----
From: Silence [mailto:semh9228 at oberlin.edu]
Sent: Tuesday, August 25, 1998 8:34 AM
To: synth-diy at mailhost.bpa.nl
Subject: Exciter


As I understand it,
The exciter filters out everything below a certain frequency, let's say,
5Khz.  It then distorts these frequency bands, and then mixes the original
signal with the modified signal.  The output then sounds 'brighter'
because it actually adds harmonics that weren't originally present in the
signal.  It was really a novelty at the time.  Speaking of tubes, the
original was accidentally created when one of the design guys at Aphex
incorrectly assembled a tube amp.  The result was what is
considered to be the first 'psycho-acoustic' enhancer.  The first design
was so secret that they wrapped the entire circuit in epoxy, and only made
the unit available for rental, it could not be purchased.  You can see why
they might write into EM with copyright complaints.  I have never seen the
schematic for the original, but I think that other circuits sound just as
good.  Just split a signal, send half through a hipass filter and the
distortion circuit of your choice, and then mix the two signals back
together.  There you go.  I have heard most of this second hand so please
correct misinformation.  Thanks.

				Eli