Diamond Halo Chorus User Manual
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Halo Chorus
Stereo chorus / vibe guitar effect pedal
User Manual
v1.01 • October 11, 2006
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INTRODUCTION
Thanks for purchasing a Diamond Halo analog stereo chorus with parallel phase modulation. 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 stereo 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 playing 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 choruses, 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 image 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 double ‘<<’ 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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3. For mono input, stereo output operation, plug into the ‘<’ input and both ‘<’ and
‘<<’ outputs.
4. For full stereo operation, plug into both ‘<’ and ‘<<’ inputs and outputs.
5. Adjust controls to suit. ‘SPEED’ affects the LFO speed for both chorus modulation and phase modulation effects. ‘CH DEPTH’ controls the amount of pitch
detuning of the delayed chorus signal, while ‘CH MIX’ controls the amount of
delayed chorus signal added in with the direct signal. ‘PM MIX’ controls the
amount of phase modulated signal added in with the direct signal.
6. The ‘<’ and ‘<<’ markings next to the control names indicate which channel is
affected by that control when operating in the stereo modes – in stereo, the ‘<’
channel carries the chorus signal, and the ‘<<’ channel carries the phase modulated signal. In mono only operation, all controls (with the exception of 180 deg
phase inversion) affect the ‘<’ mono channel as both chorus and phase effects are
mixed together into the ‘<’ channel output. The 180 deg phase inversion feature is
inoperative during mono operation.
If you’ve got two amps that you can hook it up in stereo, we highly recommend it. You’ll
be hooked on stereo!
FEATURES
parallel combination of delay / pitch modulation and phase modulation gives versatile
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control over modulation effects from light chorusing to deep 'vibey' swirl
stereo operation gives wide stereo image spread while preserving the original guitar
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tone
NOS MN3007 analog bucket brigade chip running at 15V rails for extended headroom
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dual opto 'vibe' phase modulation path also running at 15V rails
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all analog circuitry
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auto-configures for mono, mono in / stereo out, and stereo in / stereo out operation
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pure sinusoidal LFO using a dedicated function generator IC for smooth modulation
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with variable 'SPEED' and chorus pitch modulation depth 'CH DEPTH'
'CH MIX' and 'PM MIX' controls allows independent control of chorus and phase
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modulation mix levels in both mono and stereo configurations
kill-dry switch for parallel FX loop operation or use of chorus path for pure vibrato
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mono input signal passed through to both outputs on bypass
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phase switch to invert phase of right channel output relative to left
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LED indication of LFO speed, visible while in bypass
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expression pedal control of LFO speed
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same Vishay JFET / audiophile Burr Brown opamp signal path as in Memory Lane de-
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lay
telecom grade relay switched true bypass operation on all inputs and outputs
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internally regulated to 15V, can be run from provided 24V adapter or from 18V pedal
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board power supply outputs (including Y-cable powering from two 9V outputs on the
Voodoo Labs Pedal Power 2 Plus)
genuine Hammond cast aluminum 4.7 x 4.7 x 1.0 inch case
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