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The Tonebone Headlight™ is a compact amp selector that lets you connect your guitar and send the signal out to as many as four amps at once. The cool thing here is that unlike other switchers that employ dedicated footswitches to turn on or off amps, the Headlight features a single footswitch that sequentially rotates through the outputs depending on how many amps are connected. This allows the Headlight to be used as a typical ABY with two outputs, as a 3-output ABC switcher for clean, rhythm and lead amps, or switch between four amps to find the ultimate tone in the studio.

The second footswitch features two modes whereby it can be used to mute all of the outputs for quiet on-stage tuning or can be used to turn all of the amps on at once. This opens the door to greater creative uses onstage and in the studio alike.

Making connections

Before making connections, ensure your amp is turned off or the volume level is turned down. This will eliminate connection transients from damaging more sensitive components. There is no power switch on the Headlight. As soon as you connect a 9V power supply, it will come to life. The Headlight employs a typical 9V Boss®-style power supply (not included), and requires a minimum of 80mA of current with a center-pin negative connector.

Plug your guitar into the Headlight INPUT using a standard ¼" coaxial guitar cable and connect your first amp to OUTPUT-1. Output-1 is the default amp and should always be connected as it provides a safety electrical ground path to the guitar. Slowly turn up the volume on your amp to a comfortable listening level. Make sure all of the ground lift switches are in the DOWN position. This allows the switching jacks to perform properly, and will prevent the SELECT footswitch from toggling through unused outputs. With only one amp connected, depressing the output SELECT footswitch will not change the status. Add a second amp to OUTPUT-2 following the same process. Now, when you depress the selector footswitch, it will toggle the output and associated LED indicator between amps 1 and 2. You can now repeat the process and add a third or fourth amp.

Connecting a tuner

The Headlight is equipped with a dedicated TUNER OUTPUT and MUTE FOOTSWITCH. The tuner out is always on, allowing you to monitor your tuning on the fly or (using the footswitch) mute the signal going to the amps for quiet on-stage tuning. Having a separately buffered, dedicated tuner out helps eliminate clocking noise that can become audible if using an ultra-high gain amp. To mute the amps, simply depress the mute footswitch and the MUTE LED will illuminate. You can now tune without upsetting the audience.

Turning all amps on

The mute footswitch is actually a dual-function footswitch that can also be used to turn all of the amps on at once. To do this, push the MUTE STATUS SWITCH down to the ALL ON position. For instance, in this mode, with two amps connected you can now set the Headlight up as an ABY switcher. The right hand select footswitch will now toggle between output-1 and output-2 while the mute footswitch will turn them both on at the same time.

Inside the Headlight is a series of four jumpers. This allows you to configure the Headlight ALL-ON footswitch function so that it turns any or all amps on when depressed. It comes factory set with all four jumpers in place, meaning that when depressed, the output going to all amps will be activated. Pulling out the jumpers for amps 1 and 2 will result in amps 3 and 4 turning on when the ALL-ON (mute) switch is depressed. Keep in mind that this is not a toggle switch, it is an add-on switch. So if you are playing through amp-1 (output-1 active) and depress the ALL-ON switch, output-1 will still be active while outputs 3 and 4 are brought into play.

Lifting the audio ground

When more than one amp is connected, you can sometimes encounter excessive noise, commonly referred to as a ground loop. The best way to prevent hum and buzz in your system is to connect all of your amps and pedals into a single power bar. This helps prevent problems due to improper household electrical wiring. You do however, have to keep in mind that most electrical power circuits are limited in the available current. Exceeding the current demand may cause the breaker to blow. Driving three or four 100 watt amps at the same time along with a bunch of pedals may exceed the limit – so you may need to connect to two circuits if playing loud.

To help eliminate noise, the Headlight is equipped with isolation transformers and ground lift switches. Output-1 is the default amp and should always be connected to an amplifier that is equipped with a proper U-ground. The other 3 outputs are transformer isolated to block stray DC voltage and are very effective at reducing noise. These 3 outputs are also equipped with ground lift switches that lift the audio ground without affecting the safety of the electrical ground. Never cut or disconnect the electrical safety ground from your amplifier as this is there to protect you.

IMPORTANT SAFETY NOTICE: As you are the sole user of the Headlight, you are entirely responsible for using amplifiers, power supplies and effects that are electrically approved by your local authority and are safe for use. If you are unsure of the status of your equipment, please contact the manufacturer or dealer for details. As Radial Engineering Ltd is unable to control what is being connected to the Headlight, you agree to take full responsibility for its safe use and agree that Radial Engineering Ltd. along with its staff and directors shall not be held responsible in any way for damages of any kind other than those clearly detailed in the Radial Warranty. Should you for any reason feel uncomfortable with the above statement, you should return the Headlight before use to the dealer in the original packaging for full credit within 7 days of purchase.

Making sure your amps are in phase

Another important feature on the Headlight is the 180° polarity reverse switch that is found on outputs 2, 3 and 4. This is used to reverse the polarity of the amp that is connected as a means to bring all of your amps into the same absolute phase. In other words, when all your amps are in phase, all of the speakers are pushing forward when played together.

When using only one amp at a time, you will probably not notice if your amps are in or out of phase with each other as phase cancellation is most audible when two amps are on at the same time. However, when more than one amp is on, certain frequencies will either combine and get louder when ‘in phase’ or cancel out when ‘out of phase’ and sound distant. This is most audible in the lower bass range.

The easiest way to test for phase is to face your two amps together (speaker to speaker) and listen. If the sound is weak or distant in the bass region, the amps are likely out of phase. Set the mute function switch to the lower (ALL-ON) position and depress the footswitch so that all amp outputs are on. Using output-1 (amp-1) as the reference, try toggling the output-2 (amp-2) 180° polarity reverse switch to compare. If using more than 2 outputs (or amps), repeat the process with each subsequent amp – always using output-1 (amp-1) as the reference.


Headlight with 4 amps on stage

This is the guitar aficionado’s ultimate setup. Output-1 is connected to a Fender Twin® for a clean tone, output-2 to a Jazz Chorus® for a stereo effect, output-3 to a Marshall® for crunchy rhythm and output-4 is connected to a small 20-watt amp for soloing at volume 10. Connect a tuner to the dedicated output and use the mute footswitch to turn the amps off when needed.

Reamping in the studio with the Headlight

This setup is often used in the studio where you may want to Reamp a track and then compare various amps to hear which one would best be suited for a given track. In this setup, you would connect the balanced output from your workstation to a Reamper like the Radial X-Amp™. The hi-Z out from the Reamp would then connect to the Headlight and your four favorite amps and effects.

Headlight as an ABY

Connect two amps from the Headlight using outputs 1 and 2. Set the mute function switch to the inward position so that when the mute footswitch is depressed, both amps will play at once. You can then add effects pedals before or after the Headlight to create various setups. Select between the two amps using the select footswitch or have both amps play at once using the mute footswitch.

Headlight as ABC switcher

One of the more common setups is using the Headlight as an ABC switcher. With this arrangement, you can arrange your guitar amp setup using a Fender Bassman® for clean, your trusty old 50 watt Hiwatt™ for rhythm and your Mesa-Boogie® for lead.

Using the Headlight to switch between channels

You can also use the Headlight to toggle between two channels if you do not have channel switching capabilities. Older vintage amps tend to be limited in this fashion. Simply connect the channel-1 output from the Headlight to the channel-1 input on your amp and Headlight output-2 to channel-2 on your amp. You can now switch between channels like a pro!

Driving multiple pedal chains

Another fun approach is to take the output from the Headlight and feed various pedal chains. These can then either connect to specific amps or be recombined using the Radial Mix-Blender™. This innovative pedal is able to mix two signals together and send the combined signal to an amp. This can also be used in conjunction with the Radial 500™ series rack and SubMix™ module for recording purposes.

Acoustic guitar to 3 channels on a mixer

Use the Headlight to switch between 3 or 4 channels on a mixer using output-1 to channel-1 for dry, output-2 to channel-2 to add reverb, output-3 and channel-3 set louder for soloing and if you like, output-4 to insert a crazy stereo effect on channel-4.