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"The Switchbone
is simply the best AB-Y box I have ever used."
~ Doug Doppler
(Favored Nations recording
artist)
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 Using
the Switchbone |
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Switchbone
Audio Path
The Switchbone is, in fact, a unity gain amplifier
or buffer that takes an input signal from the guitar
and duplicates it at each of the two amp outputs
and the tuner output. In technical terms, one would
call this a high-impedance signal distribution amplifier.
Without amplifying the signal to bring it back up
to unity gain, the guitar would sound weak, lack
punch and body.
Based on the critically acclaimed Radial JD7 Injector,
the Switchbone’s primary signal path is pure
Class-A for minimal coloration. Class-A circuits
are the preferred choice in tube amplifiers and
audiophile stereo systems due to their natural sound.
We do not use chips or op-amps in the primary audio
circuit. Class-A circuits are less ‘efficient’
than typical AB (push-pull) circuits but with Radial
Switchbone, our primary concern is sound quality.
When amplifying a high-impedance low-level guitar
signal, introduction of noise can be a major concern.
To reduce noise and interference, the Switchbone
comes with an external 15-Volt power supply. Keeping
the supply away from the circuit significantly lowers
inducted interference and noise. The Switchbone
also incorporates a floating circuit and ground
plane to further suppress internal and external
induced noise caused by stray magnetic fields.
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Drag™ Control
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Drag™
Control |
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Switchbone's Drag™
control adds the magic that makes your guitar
sound 'right' - just like it does when you
connect directly to an amplifier.
The control is recessed, as is the VariBoost™
gain, to prevent these settings from accidental
'adjustments'. |
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When a guitar is connected directly to an amplifier,
the pickup and the amp join to form an electrical
circuit. The length of
the guitar cable, the cable’s resistance and
impedance, not to mention the amplifier’s
input impedance and the load it exhorts on the pickup,
will all combine to affect the guitar tone. This
relationship is part of the magic that makes a great
guitar and amp combination sound the way it does.
As detailed in the previous section, the Switchbone
amplifies the guitar signal so that the incoming
level is duplicated at both guitar amplifier outputs
and the tuner output. The problem here is that the
natural relationship between the pickup and amplifier
is lost. The Switchbone’s exceptionally clean
circuit is, in fact, too perfect. It provides a
perfect load on the pickup and a perfect source
to the amp. Drag™ solves the problem by allowing
the user to reintroduce a load on the pickup, which
in essence, fools the pickup into thinking it is
connected to the amplifier. This simple control
is easy to use and is extremely musical. Simply
set the Drag at 12 o’clock and listen. Each
guitar is slightly different and requires Drag™
adjustment to achieve the perfect sound. For instance,
a Fender Strat ™ connected to a Twin™
sounds right at around 12 o’clock.
Amplifier Outputs
Note: If you intend to use older, ungrounded vintage
amps, please read the 'warnings' section in the
user
manual first!
The Switchbone has two amplifier outputs. Output
1 (A) is a direct out and should be connected to
your newest amplifier, as this is where the Switchbone
will be grounded. Note that many older 'vintage'
amps are not equipped with a safety ground. Non-grounded
amps should be connected to Output 2 (B) as this
output is transformer-isolated and equipped with
a ground lift switch and polarity reverse.
Transformer isolation removes hum and buzz caused
by so-called ‘ground-loops’. The Switchbone’s
custom-designed transformer isolates the current
between the two amplifiers while the ground-lift
switch disconnects the ground path between the Switchbone’s
output-2 and the amp for 100% isolation. The polarity
reverse switch allows one to ‘align’
your amplifiers in-phase to compensate for the way
the amplifiers have been designed. Keep in mind
every amplifier company does things differently
and the Switchbone has been designed to work with
any setup!
Switching and LED indicators
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ToggleMode™
Switching |
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A solid LED indicates the amp channel currently
selected. The TOGGLE switch routes the signal
to either OUT-1 or OUT-2.
The BOTH switch routes the signal to both
OUT-1 and OUT-2. A flashing LED indicates
this output will be OFF when you hit the BOTH
switch again.
Pressing TOGGLE while BOTH outputs are selected
changes the flashing LED to the other channel.
Hit the BOTH switch again to revert to single
channel operation – the SOLID (not flashing)
LED and channel will remain ON, and the previously
flashing LED and channel will be OFF. |
AB-Y amp switching is performed with two footswitches
that are optimized to do away with ‘tap-dancing’.
The center switch is an AB ‘amp toggle’
selector while the left-hand switch is a ‘both’
or ‘Y’ selector. A series of LED's provide
quick and intuitive amp status read-outs allowing
the player to toggle between amps or between one
or two amps quickly.
The Switchbone’s LED status indicators are
large and easy to see. In AB toggle mode, the light
goes on when the amp output is on. Simple. However,
when ‘Both’ amps are turned on, one
LED will be illuminated while the other will flash.
This lets the player know that the flashing output
will go off when going back to single amp operation.
To eradicate switch noise, the Switchbone employs
a series of lightning-fast opto-coupler instead
of relays. The opto-couplers are, in fact, electronic
switches that are controlled by the footswitch and
perform the same function as a relay. Although more
expensive, these do not suffer from contact degradation,
mechanical failure or arcing – typical problems
that relays introduce. The biggest advantage is
zero switching noise as these eliminate any mechanically
induced electronic contact spark. The result is
whisper-quiet switching even when used with ultra-high
gain amplifiers.
Power Booster Circuit
The Switchbone incorporates VariBoost™, a
simple yet extremely effective power booster. This
has been added for several reasons, the most obvious
being that when using two amplifiers, boosting the
level of both amps at the same time for solos would
be practically impossible. The power booster also
serves another important function by allowing the
user to compensate for volume when going from two
amps down to one.
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VariBoost™
Power Booster
Switchbone's Power Boost controls, variable
gain and noiseless switching adds a practical
level matching function as well as extra 'kick'
for soloing. The Gain control on the front
panel is recessed (see above) to prevent accidental
bumping of this setting. |
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There are three controls plus an activating footswitch
for the VariBoost. These include a variable gain
control – a function switch that selects between
gain boost, mid and gain boost or mute. The mute
turns off the amp outputs while still sending signal
to the tuner out. The mid selector switch features
bypass, and two mid boost intensities.
Tuner Output
The Switchbone is equipped with a separate buffered
tuner output that is always on. This has been designed
to allow 'on-the-fly' tuning no matter what the
settings on the Switchbone. The Switchbone lets
you mute the amplifiers by setting the power booster
selector switch to the mute position and depressing
the 'BOOST' footswitch. This allows quiet tuning. |
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