Radial Headbone VT Tube Amplifier Head Switcher User Guide
- June 4, 2024
- Radial
Table of Contents
Radial Headbone VT Tube Amplifier Head Switcher
Congratulations on your purchase of a Radial Headbone!
The Headbone VT provides the discerning guitarist with options to achieve
creative new sounds with a simple, yet extremely versatile interface. The
Headbone VT is designed to connect two tube amplifier heads to one speaker
cabinet and switch between amplifiers with either the onboard or remote
footswitch. The Headbone uses pure Class-A electronics under digital control
to switch the hi-impedance guitar signals and speaker-level outputs from your
amps. Best of all, the Headbone is engineered to ensure the safe operation of
your amps under demanding live performance conditions. To take advantage of
the wonderful features that have been incorporated into the Headbone, please
take the time to read through this manual before you use it. This will give
you a broader sense of the Headbone’s capabilities and ensure its safe and
proper operation. If you have questions that are not covered here, please
visit www.radialeng.com for additional resources.
INTRODUCTION
IMPORTANT
Attempting to use a solid-state amp with the Headbone VT could damage your
amp and/or the Headbone. This would void your warranty. Please consult your
dealer and make sure you fully understand the ownership disclaimer on the
inside cover of this manual before using the Headbone. When developing the
Headbone, we asked guitarists: “What would be the ultimate guitar setup?” Ask
10 guitarists this question and you will likely get 10 different answers. The
reason for this is simple: There are no right answers as the possibilities are
endless. So where do you start? You need a concept. The following is a setup
concept that will help get those creative juices flowing. It combines
simplicity with awesome stage performance. In the example below, amp head-A is
a 100-Watt 2-channel amp with one channel set to clean and the other set to
saturated distortion. Amp head-B is a low-power 30-Watt amp that would be
driven ‘hard’ for natural power-tube overdrive. In between the amps and a
single speaker cabinet sits the Headbone, allowing you to select between amps
with a remote footswitch on your pedalboard. Add a good distortion pedal and
your setup becomes a tone monster.
Why is this setup so cool? Because it truly covers all of the bases: the powerful clean sound from a 100-Watt amp is radically different than a cranked all-tube 30-Watt amp. A Headbone setup lets you quickly access the tones from two amps with the convenience of footswitch control right on your pedalboard. Best of all, you only have to carry around a single speaker cabinet – a luxury that is best appreciated at two in the morning after the gig!
Tone chart: two amp heads, one distortion pedal, one speaker cabinet, six
distinct amp tones.
With the Headbone in your rig, you are now able to specify which amplifier you
will use for a particular song, passage or even phrase. You do not have to
compromise your tone, or carry around two amp stacks to get there. Headbone
adds tonal flexibility while reducing the amount of equipment you must bring
to the gig! More tone with less gear.
FEATURE SET
- Input Buffered – This is the primary input for your guitar and pedal effects that do not buffer (pre-amplify) the signal.
- Input Direct – Used when driving the Headbone from a device, like the Radial Loopbone, that buffers (pre-amplifies) the signal.
- To Amp-A Input – This is a ¼” hi-impedance guitar signal output that connects from the Headbone to the input of the first guitar amplifier.
- To Amp-B Input – This is a ¼” hi-impedance guitar signal output that connects from the Headbone to the input of the second guitar amplifier.
- Ground Lift – This recessed switch connects the ground to Amp-B. This switch is factory set in a ‘lifted’ position to eliminate ground loops.
- Slingshot Remote Input – This ¼” input is used to remotely control the Headbone from your pedalboard using a standard contact closure footswitch or another Radial device that features a Slingshot output.
- From Amp-A Output – Connects from the first amplifier’s speaker output jack back to the Headbone. This is a speaker-level signal, so use a good quality speaker cable for best power transfer.
- From Amp-B Output – Connects from the second amplifier’s speaker output jack back to the Headbone.
- To Speaker Cabinet – Connects the Headbone to your speaker cabinet.
- Power Supply Connection – The Headbone comes with its own 15VDC power supply.
- Footswitch – Used to toggle the Headbone between Amp-A and Amp-B
- LED Indicators – Indicates which amplifier head is active.
QUICK START
Important:
- Before making any connections, ensure that your amplifiers are turned off, the Headbone power supply is disconnected, and volume controls are set to zero.
- Throughout this manual, references are made to “guitar level signals” and “speaker level signals”. The Headbone passes both types and it is important to use the proper cables.
- A guitar-level signal requires a good quality shielded cable to work well. High-quality guitar cables with proper shielding will help reduce system noise and radio interference.
- Speaker-level signals require good quality unshielded speaker cables. We recommend using a minimum of 14 AWG cables for speaker cables run under 6 feet. Larger gauge cables should be used for longer runs. Never use shielded guitar cables for speaker connections.
- Begin by connecting your guitar to the Headbone’s ¼” Buffered Input. This will allow you to test the system more effectively during the initial setup. For unbuffered (Direct) input use, please go to the section that discusses this on page 7.
- The Headbone VT is designed for tube amps exclusively.
- From the Headbone, connect the To Amp-A Input jack to your first amp’s guitar input. This circuit connects the guitar to your first amp.
- From the Headbone, connect the To Amp-B Input jack to your second amp’s input. This circuit connects the guitar to your second amp.
- From your first amp’s speaker output, connect to the Headbone’s From Amp-A Output jack. This brings the signal from amp-A back to the Headbone.
- From your second amp’s speaker output, connect to the Headbone’s From Amp-B Output jack. This brings the signal from amp-B back to the Headbone.
- From the Headbone To Cabinet jack, connect to your speaker cabinet. You are now ready to start system tests.
- Connect the Headbone’s power supply. The Headbone will turn on and you will see one of the LEDs illuminate.
- You can now turn on your guitar amplifiers. It is a good practice to test equipment setups at a low volume to reduce any possibility for system damage should there be an improper connection. Turn up the volume slowly while listening for excessive noise. Depress the footswitch to make sure both amps are working.
GETTING TO KNOW YOUR HEAD BONE
To best explain the workings of the Headbone, take a minute to study the block diagram. Reading from left to right, you can see the inputs, the high- impedance guitar switching, the control circuitry and the speaker level switching.
The Input Signal Path
The Radial Headbone’s input signal path is 100% discreet Class-A. This means
that it employs a whole bunch of parts such as resistors and capacitors
instead of a transistor to buffer (amplify) the guitar signal to a manageable
level. Class-A circuits are preferred over integrated circuits (IC chips) as
they are more natural sounding.
Buffered and Direct Inputs
The Headbone gives you the choice of two inputs: one buffered and one direct
or unbuffered. The reason we do this is that when you are driving a pre-
buffered signal, there is no advantage to buffering the signal again. In some
cases, two buffers in series could add distortion or noise. If you are
connecting the guitar directly to the Headbone, use the Buffered Input. If you
use a buffering device (pre-amp), such as the Radial Switchbone, you would
plug the output of the device into the unbuffered Direct Input. Some effect
pedals use a buffering stage in their design, some do not. If you are
connecting an effect pedal before the Headbone, the best way to decide which
input to use is to let your ears choose the one that sounds best to you.
Switching Guitar Signals
The Headbone simultaneously switches the inputs to the amps as well as the
outputs from the amps. It is important that the input going to the unused head
be disconnected so that, while in standby, it is not trying to amplify a
signal with anywhere to go. The Headbone performs silent guitar signal
switching with a series of optocouplers under digital control. These
optocouplers are made to ramp up and ramp down the guitar signal in such a way
as to avoid any clicks or pops from the mechanical footswitch. The digital
controller is programmed to perform this cross-fade over a few milliseconds
making it impossible to hear while effectively eliminating noise.
Switching Speaker Signals
To accomplish this task, the PIC sends a status change command to a series of
internal relays that connect the speaker to the active amp, and connect the
load resistor to the standby amp. Always use good quality, large conductor
speaker cable between the Headbone, your amps and your speaker cabinet, as
this will reduce signal loss and improve the transient response. Your Headbone
has been designed to work with amps whose maximum output is 100 watts RMS. The
power is limited by the relay that is used to switch the speaker signals. To
be safe, never exceed this power limit.
IMPORTANT:
Effects such as echo or loop-playing devices MUST BE CONNECTED BEFORE the
Headbone so that their residual or sustaining sound can be disconnected from
the input of the amplifiers. This means that you cannot use any type of echo
device that prolongs a signal on the amplifier’s effects loop or after the
Headbone in your signal chain. Failure to do so could cause the echo to
continue to play through the standby amp which, in turn, would continue to
amplify the signal without a load. This could cause the amp or the Head-bone
to malfunction. The Headbone’s internal resistor load is only designed to
support the standby amplifiers residual output. The Headbone is NOT a load
box.
Matching the Speaker Load
The Headbone itself has no effect on amplifier load or speaker impedance. You
must manage the speaker connections for the best impedance match. It is
important to note that most amplifiers are designed to work best at their
rated impedance. If your amp features selectable impedance loads, use the one
that matches your speaker cabinet. Always consult the amplifier’s
specifications to ensure the speaker connections are within the amplifier’s
accepted working range. While matched loads between the amplifier and speaker
are ideal, unmatched loads can be used. The guidelines below will explain the
ramifications of using unmatched loads.
Using Unmatched Speaker Loads With Tube Amps
Driving a speaker load that is lower than the amp’s output impedance (8-Ohm
amp with 4-Ohm speaker) tends to drive the tubes harder, which means they will
not last as long. On the other hand, a higher speaker impedance load (4-Ohm
amp with 8-Ohm speaker) will generally sound less full and less punchy, but
tube life is extended.
Grounding for Safety!
The Headbone is powered by an external power supply with a floating ground.
This means that the guitar derives it’s ground thru the amplifier connected to
the Headbone’s To Amp-A Input jack. The To Amp-B Input jack is transformer-
isolated from the ground to eliminate hum or buzz caused by so-called ground
loops passing between amp-A and amp-B. A recessed ground-lift switch is
provided to bypass the transformer and reconnect the ground through amp-B. The
switch is factory set in the lifted position Should the amplifier connected to
the To Amp-A Input jack not be properly grounded, this switch may be depressed
to connect the ground path through amp-B. For safety, always use properly
grounded guitar amps with 3-prong electrical AC plugs. The third prong is a
safety ground that protects you from electrical shock. Most amplifiers have
been subjected to safety tests from authorities like UL or CSA. Amplifiers
that have passed these tests are safe to use with your Headbone. If you intend
to use the Headbone with amps that only have 2-prong AC plugs, such as old
vintage amps, you are doing so at your own risk. Please consult a qualified
technician if you are not sure how to establish a safe ground connection.
Safe Mode™ Operation
One of the really smart features in the Headbone is a function called Safe-
Mode. Should the Headbone’s DC power supply be disconnected, the system will
‘default’ to Safe Mode, whereby AMP-A’s input and output will automatically
connect to the speaker cabinet. This simple, yet extremely important safety
feature, will ensure that the active guitar amp always “sees” a load and that
the standby amp is muted.
Slingshot Remote
The Slingshot feature allows you to position the Headbone adjacent to the
guitar amplifier setup and remotely control it from a distant footswitch. With
Slingshot, you can avoid a mess of spaghetti by keeping the cables between the
Headbone, amps, and speaker short. This also improves amplifier efficiency and
reduces system noise.
The Headbone’s Slingshot Remote is a simple contact closure that allows a
standard ‘latching’ footswitch to remotely toggle the Headbone’s status from
amp-A to amp-B. Most standard ¼” mono-style footswitches will work. The
Headbone may also be used with Slingshot-equipped pedals such as the Radial
Loopbone. Other pedal-switching devices or MIDI controllers that are equipped
with a contact closure output will also be able to toggle the Headbone.
Remote Footswitch Schematic
Use this drawing for making your own remote footswitch.
Use an SPST push-on/push-off type footswitch. If you wish, an optional LED can be included in the circuit. Any standard size ( T-1 or T-1 3/4 ) red LED with forward voltage between 1.6 & 2.2 volts (current = 20ma) will work. The LED will light when AMP-2 is active. Connect the switch to the Slingshot Remote input on the Headbone with a two conductor cable. Connecting a remote footswitch to the Headbone will disable the onboard footswitch. If you are unsure of these requirements, please refer to a qualified electronic technician.
FAQ
-
Q: I heard that tube amps must always see a speaker load or else they will become damaged. Is this true?
A: This is true. To deal with this, the Headbone is equipped to manage two loads: the speaker for the active amp and a load resistor for the standby amp. The Headbone transitions between these two loads when the footswitch is toggled. -
Q: Is the Headbone a load-box?
A: No. A load-box is designed to absorb an amplifier’s full output and pass a reduced amount of power to the speaker. The Headbone uses a much smaller load resistor to provide an idle load for the standby amplifier. -
Q: Why does the Headbone use an optocoupler and relays to switch the guitar and amp signals?
A: To switch active signals a circuit designer must choose between voltage- controlled amplifiers (VCA’s), optocouplers, relays, or converting the signal to digital and then back to the analog domain. The type of guitarist that uses a Radial product is generally a purist and is very concerned about retaining the natural tone of his instrument. VCA and digital circuits are not acceptable as they change the tone of the instrument. Radial products use optocouplers on the hi-impedance circuits to eliminate all switching noise and relays on the speaker level signals where high voltage is present. -
Q: I have heard that using an echo with a head switcher can cause a problem with the amps. Is this true?
A: It depends on where the delay is positioned in the signal chain. If the delay is placed before the Headbone, there is no problem. If the delay device is placed after the Headbone, or in an amplifier’s effects loop, you can have a problem because the echo may continue to generate a signal and send it through the “stand-by” amp with no speaker load connected. It is generally not good to run an amp this way as the output transformer can heat up and ultimately short out. Thus, always put delay and looping devices before the Headbone in the signal chain. -
Q: Can I use the Headbone like an A/B box?
A: It certainly could be done, but you may encounter ground loop problems as the Headbone is not set up for this function. The Radial Switchbone would definitely be a better choice. -
Q: Can I use the Headbone with a MIDI switcher?
A: Yes. Most MIDI switchers are equipped with a contact closure output jack. This would be connected to the Headbone’s Slingshot input to remotely control amp switching. -
Q: If I do not want to use the Slingshot remote, how far from the amps and speaker can I be?
A: As a general rule, we do not recommend running cables any more than 20 feet as you are subjecting the signal to increased resistance. If you are intent on doing so, use good-quality cables. For speaker connections use large gauge (12AWG) speaker cables. For guitar signals use low capacitance shielded cables. -
Q: How do I know if my footswitch will be Slingshot compatible?A: If your external footswitch employs a basic latching type switch with a ¼” or ¼” TRS connector it will, in all likelihood, be compatible. If it employs some type of multi-pin connector or telephone-style jack, it may not. Consult your dealer or manufacturer for advice on how you can make an adaptor that will allow you to enjoy the benefits of the Headbone’s Slingshot.
-
Q: Can I use another power supply other than the 15VDC that comes with the Headbone?
A: No. Never use another power supply unit other than the one included with your Headbone. Because of the Headbone’s Class-A circuit, a more powerful 15VDC supply is required. If you need a replacement power supply, contact your Radial dealer.
RADIAL ENGINEERING 3-YEAR TRANSFERABLE WARRANTY
RADIAL ENGINEERING LTD. (“Radial”) warrants this product to be free from
defects in material and workmanship and will remedy any such defects free of
charge according to the terms of this warranty. Radial Engineering will repair
or replace at its option any defective component(s) of this product, excluding
the finish, the tube, the footswitch (tubes and footswitches are warranted for
90 days) and wear and tear from normal use, for a period of three (3) years
from the original date of purchase. In the event that a particular product is
no longer available, Radial Engineering reserves the right to replace the
product with a similar product of equal or greater value. In the unlikely
event that a defect is uncovered, please call
604-942-1001 or email
service@radialeng. com to obtain an RA number (Return Authorization number)
before the 3-year warranty period expires. Once you have obtained an RA number
you must return the product, freight prepaid, within fifteen (15) days after
the date the RA number is issued. The product must be returned prepaid in the
original shipping container (or equivalent) to Radial Engineering or to an
authorized repair center and you must assume the risk of loss or damage. A
copy of the original invoice showing date of purchase and the dealer name must
accompany any request for work to be performed under this limited and
transferable warranty. This warranty shall not apply if the product has been
damaged due to abuse, misuse, misapplication, accident or as a result of
service or modification by any other than an authorized repair center.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE ON THE FACE HEREOF AND
DESCRIBED ABOVE. NO WARRANTIES WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT
LIMITED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE SHALL EXTEND BEYOND THE RESPECTIVE WARRANTY PERIOD
DESCRIBED ABOVE OF THREE YEARS. RADIAL ENGINEERING SHALL NOT BE RESPONSIBLE OR
LIABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES OR LOSS ARISING
FROM THE USE OF THIS PRODUCT. THIS WARRANTY GIVES YOU SPECIFIC LEGAL RIGHTS,
AND YOU MAY ALSO HAVE OTHER RIGHTS, WHICH MAY VARY DEPENDING ON WHERE YOU LIVE
AND WHERE THE PRODUCT WAS PURCHASED.
Radial Engineering
1165-1845 Kingsway Ave, Port Coquitlam BC V3C 1S9 Tel:
604-942-1001 •
www.radialeng.com
Email: info@radialeng.com
Radial Engineering Ltd.
Headbone VT Owner’s Manual – Part # R870 1075 00 • 03-2021
Specifications and appearance are subject to change without notice.
References
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