INTRODUCTION
Thanks for purchasing a Diamond Halo analog stereo chorus with parallel phase modula-
tion. This unique combination of chorus pitch and phase modulation using a smooth sine
wave low frequency oscillator, coupled with auto routing for mono to mono, mono to ste-
reo and stereo to stereo operation, gives an incredibly versatile analog modulation tool for
everything from subtle spatialization to deep pitch and amplitude modulated swirl effects.
Remember to protect your hearing and wear appropriate hearing protection when play-
ing loud…
DESIGN BACKGROUND
Originally, we envisaged the Halo Chorus as a dual delay path chorus device, one in
which separately modulated bucket brigade devices would be assigned to left and right
channels in stereo, and combined together for a multi-voice mono chorus configurations.
The plan was that the slightly different delays in each channel along with some LFO
tricks, would give a wide stereo image, and a thicker chorus effect in mono. After the first
couple of prototype boards, it became clear that adding the second voice wasn’t going to
be enough of a benefit to stand out from existing phase-reversed single voice stereo cho-
ruses, and certainly not enough to warrant the additional infrastructure required for the
second bucket brigade voice. Back to the drawing board we went…
We looked again at what could be done psychoacoustically to generate a wide stereo im-
age without necessarily inverting the phase of the second output channel (although this is
also included and switchable on the Halo). Although there was never any intention to
build a rotating speaker simulator, we looked at their basic physics and decided that the
inclusion of some mild phase modulation (and its resulting amplitude modulation) might
integrate very well with the pitch modulation of the chorus effect. So, we decided to build
a simple photocell based two stage phase modulation circuit, and assign this to its own
parallel channel in place of the second chorus circuit. When we got the first proto Halo
board with the phase modulator soldered and into a box, we hooked it up immediately in
stereo to see what the effect would be…and after a couple of minutes of playing, we were
certainly glad the two chorus path design didn’t work out.
QUICK SETUP
Although we strongly recommend reading the entire user manual before getting started,
here’s a few tips for quick setup:
1. Input and output channels aren’t labeled ‘left’ and ‘right’, just single ‘
<
’ and dou-
ble ‘
<<
’ directional arrows (indicating channels one and two).
2. For mono operation, plug into the ‘
<
’ input and outputs (they’re also marked
‘mono’).
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Halo Chorus user manual v1.01
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