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Radial JD7 Injector

7-Way Guitar Distro and Splitter

Radial JD7 Injector

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Product Description for the Radial JD7 Injector

The Radial JD7 Injector is a guitar signal splitter that is able to drive as many as seven amplifiers at the same time and do so without the noise that often plagues most systems.

It features A or B selectable inputs with Radial's award winning class-A buffering circuit for ultra low distortion. To ensure maximum signal fidelity, Drag Control load correction lets you replicate the load on the guitar pickup as if connected to a tube amplifier for the most natural tone. The hi-Z outputs are equipped with high-performance Jensen Transformers for optimal signal transfer. Transformer isolation along with individual ground lifts help eliminate hum and buzz caused by ground loops for cleaner, quieter guitar tracks. 180º polarity reverse ensures all amps play in phase while channels 5 and 6 are equipped with effects loops for greater setup flexibility.

The JD7 is fully equipped for Reamping: a built-in Radial direct box lets you record a dry track while a separate Reamp input is ready for re-recording dry tracks when needed. This enables you to move mics around the room, change amps or add effects to optimize the sound of the recording. And Reamping works equally well on bass, voice and other instruments.

Designed to spur on creativity, the JD7 is plug & play easy to use, super quiet, and amazingly natural sounding… a guitarist's dream come true and a producer's very best friend.

This quick start is designed to give the experienced professional player and guitar tech an overview on how to use the Radial JD7.

The JD7 is a guitar splitter. The more appropriate name is a high-impedance unity-gain guitar signal distribution amplifier. It allows you to drive as many as six amplifiers; a tuner; two effects loops; and feed a recording system via the built-in direct box at the same time. Full Reamping capabilities means you can then run a dry track into the JD7 to feed the amps and effects and adjust the tone as needed.

Input connections

As with all electronic audio products, always ensure levels are turned down or equipment is turned off before making connections. This will ensure turn-on transients do not harm sensitive electronics or speakers. The JD7 comes with an external power supply. As soon as you connect it, the JD7 will turn on.

There are two inputs on the front panel designated as 1 and 2. Depressing the SELECT switch will engage the input-2 if a guitar is connected. If not, it will select the balanced XLR input on the rear panel for Reamping through the JD7.

Drag Control

The Radial JD7 is equipped with Drag Control load correction. The adjustable circuit lets you reintroduce the load on the pickup so that it sounds as if connected directly to a tube guitar amp. Start by setting the Drag Control to 12 o'clock. Listen. As you move the control clockwise, it will sound brighter. Adjust to suit.

-8dB PAD

Input-2 is equipped with a PAD that can be switched in for 8dB of level reduction. This can be helpful to match the input level between two guitars. Active pickups tend to output a hotter signal compared to passive pickups. The PAD can be used to bring active and passive guitar closer to the same input level.

Clip LED

All inputs, including the balanced XLR Reamping input, are monitored for overload by the clip LED. If the LED illuminates while playing reducing the input level going into the JD7

Grounding and connecting amplifiers

There are six outputs on the front panel. Channel-1 is designated as a 'DIRECT' output and should always be connected to a grounded amplifier, even if not used. The reason is for any electronic system to work safely it needs a path to ground. The JD7 provides this through the direct output-1 and the amp connected to it.

This means the amp your choose to connect to output-1 must have a good connection to ground. To ensure a solid ground only connect modern amplifiers that display UL and CSA certification labels and use a grounded three prong power plug. If you plan on connecting vintage amplifiers to outputs 2 thru 6 ensure that they have been modified to bring the power cord and grounding up to modern electrical safety codes by a qualified technician.

Its important to note that even through a grounded amp must be connected to output-1 at all times it does not have to be active. All amplifier outputs are equipped with ON/OFF toggle switches. You can use the toggle switch to turn the amp off while still using it as the primary path to ground.

Channels 2, 3 & 4

Output channels two, three and four feature transformer isolated outputs, an ON/OFF switch with status LED, a ground lift and polarity reverse switches. There are no volume controls on the JD7 outputs. As a unity gain device, it is designed to take whatever signal you put in, buffer it and output the same level without signal boost.

Live stages are often plagued by very powerful electromagnetic fields that can induce hum and buzz into everything! High impedance guitar circuits are particularly prone to noise. The JD7's isolated outputs can be very helpful as they naturally block DC currents which often times will cause hum and buzz when various pieces of equipment are connected together.

Channel 5 & 6 effects loop

Channels five and six are equipped with the same features plus an effect loop with rear panel send and receive jacks. Simply connect your pedals to the SEND and RECEIVE jacks and activate the loop by depressing the associated EFX LOOP switch on the front panel.

The idea here is to allow you to quickly compare the sound on outputs 5 and 6 with or without the pedals. Effect placed in the loops will be dedicated to one amp.

There are other options for effects pedals. You can dedicate an effect to one amp by placing it between the JD7 output and the amps input. You can share an effect will all amps by connecting your guitar to it before connecting to the JD7.

Connecting a tuner

Auxiliary output number seven is another buffered output identical to output one except that it is always on and can not be turned off. It can be used to drive rack tuners, in-ear systems, alternate amplifiers, the 2 channel on an already connected amplifier, to drive monitors, another direct box, etc, etc... in fact, we would love to hear how you've used this output in a creative way on your own rig.

Setting up several amps

You can drive a number of amplifiers on stage using the JD7. When connecting multiple amps it's very important to ensure your amps are phase aligned and all loudspeakers are moving in the same direction. This will allow more than one amp to play at a time with the best sound. The amp connected to output-1 is your "phase reference" amp. Amplifiers connected to the other outputs will be tested against your first amp and adjusted to match using the 180° polarity switch.

We recommend you add and test one amp at a time. The following checklist will guide you through the process of setting up each output to drive an amp without noise or phase problems.

Always start by connecting output-1 to a grounded amplifier. Check to make sure your first amp is working normally. If so, you are ready add more amplifiers.

Connect an amplifier to output-2 and turn it on at a low level. Listen for hum or buzz. If you hear noise depress the ground lift switch. This disconnects the ground to the amplifier and can often help eliminate noise from ground loops and magnetic interference.

Set both amplifiers to the same volume to begin testing the phase of output-2.

Toggle the 180° polarity switch on output-2 and compare the tone of the two settings. The in-phase setting will sound loud and full, the out-of-phase setting will sound hollow and weak. Choose the setting that sounds the best.

The 180° control inverts the signal polarity of the output causing the amps speakers to move in the opposite direction. The idea is to choose the setting where the speakers in both amps are moving in the same direction.

Once the output-2 is set up turn it off and move on to the next output and amp. Always test one amp at a time against the amp connected to output-1.

Be aware that you may introduce a new polarity problem if you change an amp or add an effect pedal after setting up the outputs. This may happen because some effect pedals invert the polarity of the signal and some amps wire their speaker(s) opposite to others. If you change something its a good idea to check phase against your first amp.

Using the JD7 for studio Reamping

Record a dry track

Reamping is a two step process where the first thing is to record a clean dry track of the players performance. Set up the JD7 with the guitar connected to it and to an amp or two so that the guitarist is comfortable. Adjust the Drag control to make it 'just so' and mic up his amps as you would normally do. Record everything to separate tracks.

Then, connect an XLR cable from the JD7's direct box output to your recording system. This is a balanced mic-level output and should connect to a mixing console or mic preamp. Record the direct box output with no EQ or effects. This will capture the clean sound of the guitar while it feeds the amps.

This clean dry track will playback an exact copy of the players performance when Reamped back through the JD7. When the guitarist whales away with feedback, the dry signal will actually capture the sustaining strings. It will blow your mind.

The guitarist should be nice and fresh and ready to play. Do not worry too much about the recorded sound; capture the moment by concentrating on the performance. Once the track has been recorded, you can now send the guitarist to the beach.Reamping the dry track

Take the clean dry track from the recording system and send it into the JD7 using the balanced line Reamp input. This is equipped with a level control that will let you adjust the signal level to replicate the original guitar level for your amps. You can connect as many amps and effects as you would like to the JD7 outputs.

Experiment with different amps and effects using various microphones and move them around the room until you get the sound you want. You can record track after track and the guitar player is no longer subjected to the painful technical details. This reduces stress for everyone! Best of all, you can always go back and Reamp the track again if later on you feel the track is not sitting quite right in the mix.

JD7 Injector Development

Radial is an instrument interface company. Our products enable guitars, basses and keyboards to connect to pro-audio gear. This is what we do and the JD7 is at the very heart of it all. In fact, the Radial JD7 was one of the first products we ever developed. And from the original design, many other products have come to market including the Radial X-Amp Reamper, the SGI Studio Guitar Interface, the Switchbone, the BigShot PB1 power booster and the Radial JX44 Air Control.

Radial President Peter Janis tells the story: I had this idea of producing a guitar signal splitter that would enable the player to drive a number of amps. As a former stage musician, I remember having three amps on stage and I was always fighting hum and buzz problems. I also knew that there were some custom made splitters that were very expensive but limited in scope. I figured we could come up with a design that would work for live players and be valuable in the studio for recording. Little did we know that the JD7 would be such a long standing success…

The basic design criterion was simple: Plug in a guitar and drive a bunch of amps at the same time. No fuss, no noise… how hard could that be?

Blame it all on Leo Fender!

We started with a basic layout: a 19" rack frame with six guitar amp outputs on the front panel plus a 7th on the back panel for a tuner. When the first JD7 prototype arrived, I took it home. Next morning, at about 7 AM I started to listen to it using a set of headphones. I remember calling Denis Rozon, the design engineer, and I told him 'it did not sound right'. He said 'that was impossible - it has a 1 meg-ohm input, is 100% discrete, equipped with class-A buffers and Jensen Transformers'. In his words: 'I tested it and it is perfect'. I told him that although it may be 'electronically' perfect, as a guitarist it did not sound right. The feel was wrong. Before I started Radial, I served 10 years as Product Director for Fender in Canada. Believe me - I know what my Stratocaster sounds like. Something was not right. Denis thought about it and a few days later, he found a solution.

Fact is, most guitarists hate the sound of buffers and solid state amps. And there is good reason! Most sound terrible! Here's the deal: When you connect a guitar to an amp, the pickup reacts with the amp and becomes part of the circuit just like a light bulb when connected to a battery. The amp's circuit affects the tone. Well, way back when Leo designed his first tube amps, he decided that a 1meg-ohm input impedance would be best. Everyone has been using a 1 meg-ohm input ever since.

But no one ever considered that tube circuits react differently than solid state ones. This is what I heard and what Denis figured out. A tube amp loads the pickup differently than a solid state amp and when you introduce a buffer, in this case the JD7 in between the guitar and the amp, the load changes. By varying the load on the pickup we can replicate the way that the guitar reacts to the amp and the sound regains the natural feel. The term 'drag' comes from a fishing rod: you adjust the tension on the reel using the drag. This is how we ended up calling it Drag Control.

How 'real' does it feel? Believe me, if you can fool Carlos Santana, Joe Perry, Steve Vai or John Petrucci into thinking they are connected directly to their amps, you know that you have it right.

Establishing the feature set

Once we got the sound right, the next step was working out the feature set. We decided to recess the Drag control for 'set & forget' simplicity. The 6 output channels on the front and a 7th on the rear for a rack-mount tuner seem to provide more than enough connectivity. We then set about working through the challenges of using various amplifiers together.

The first challenge was solving grounding problems. If you have ever Y-jacked the input a couple of old vintage amps together, you are likely aware of the dangers. Without a safety ground, you can become the ground rod and get shocked with hundreds of volts!

Grounding issues also introduce noise problems commonly known as ground loops. A ground loop is created when the electrical ground and the audio ground share a circuit. This creates a loop. In the JD7, we eliminate the ground loop by transformer isolating all of the outputs except output 1 which is the ground path. In order to preserve the most natural sound, we of course use the world's best Jensen transformers. These deliver exceptionally linear performance without artefact or distortion.

The next challenge is mixing one brand with another. Guitarists are often miffed when they discover their Fender may be out of phase with their Marshall. To solve this problem, the Radial JD7 is equipped with a series of polarity reverse switches that toggle the electrical phase so that the amps play in phase. It may be worth noting that most guitar pedals can also reverse the phase…

Finally, we decided that since pedals may be brought into the signal chain but may need to be temporarily removed to compare wet and dry signal paths, we chose to add separate effects loops on output channels 5 and 6. This way, you can bring pedals in and out by simply pushing a switch.

To Reamp is to Create!

Probably the most exciting recording processes used today is Reamping. Reamping is a process whereby you 'quietly' capture a dry track while the guitarist is recording his wet track. In other words, you record the performance while the guitarist is fresh. The guitarist does not have to sit through hours of repetition waiting for the engineer and producer to work out the sonic details. Once you have captured the magic you send him to the beach with his girlfriend. Then, you send the dry track back out to the guitar amps, add pedals and start adjusting the tone and moving the mics around until you get the sound you are looking for. Best of all, you can go back and Reamp the track later should the tone need to be tweaked.

JD7 Injector Development

Radial is an instrument interface company. Our products enable guitars, basses and keyboards to connect to pro-audio gear. This is what we do and the JD7 is at the very heart of it all. In fact, the Radial JD7 was one of the first products we ever developed. And from the original design, many other products have come to market including the Radial X-Amp Reamper, the SGI Studio Guitar Interface, the Switchbone, the BigShot PB1 power booster and the Radial JX44 Air Control.

Radial President Peter Janis tells the story: I had this idea of producing a guitar signal splitter that would enable the player to drive a number of amps. As a former stage musician, I remember having three amps on stage and I was always fighting hum and buzz problems. I also knew that there were some custom made splitters that were very expensive but limited in scope. I figured we could come up with a design that would work for live players and be valuable in the studio for recording. Little did we know that the JD7 would be such a long standing success…

The basic design criterion was simple: Plug in a guitar and drive a bunch of amps at the same time. No fuss, no noise… how hard could that be?

Blame it all on Leo Fender!

We started with a basic layout: a 19" rack frame with six guitar amp outputs on the front panel plus a 7th on the back panel for a tuner. When the first JD7 prototype arrived, I took it home. Next morning, at about 7 AM I started to listen to it using a set of headphones. I remember calling Denis Rozon, the design engineer, and I told him 'it did not sound right'. He said 'that was impossible - it has a 1 meg-ohm input, is 100% discrete, equipped with class-A buffers and Jensen Transformers'. In his words: 'I tested it and it is perfect'. I told him that although it may be 'electronically' perfect, as a guitarist it did not sound right. The feel was wrong. Before I started Radial, I served 10 years as Product Director for Fender in Canada. Believe me - I know what my Stratocaster sounds like. Something was not right. Denis thought about it and a few days later, he found a solution.

Fact is, most guitarists hate the sound of buffers and solid state amps. And there is good reason! Most sound terrible! Here's the deal: When you connect a guitar to an amp, the pickup reacts with the amp and becomes part of the circuit just like a light bulb when connected to a battery. The amp's circuit affects the tone. Well, way back when Leo designed his first tube amps, he decided that a 1meg-ohm input impedance would be best. Everyone has been using a 1 meg-ohm input ever since.

But no one ever considered that tube circuits react differently than solid state ones. This is what I heard and what Denis figured out. A tube amp loads the pickup differently than a solid state amp and when you introduce a buffer, in this case the JD7 in between the guitar and the amp, the load changes. By varying the load on the pickup we can replicate the way that the guitar reacts to the amp and the sound regains the natural feel. The term 'drag' comes from a fishing rod: you adjust the tension on the reel using the drag. This is how we ended up calling it Drag Control.

How 'real' does it feel? Believe me, if you can fool Carlos Santana, Joe Perry, Steve Vai or John Petrucci into thinking they are connected directly to their amps, you know that you have it right.

Establishing the feature set

Once we got the sound right, the next step was working out the feature set. We decided to recess the Drag control for 'set & forget' simplicity. The 6 output channels on the front and a 7th on the rear for a rack-mount tuner seem to provide more than enough connectivity. We then set about working through the challenges of using various amplifiers together.

The first challenge was solving grounding problems. If you have ever Y-jacked the input a couple of old vintage amps together, you are likely aware of the dangers. Without a safety ground, you can become the ground rod and get shocked with hundreds of volts!

Grounding issues also introduce noise problems commonly known as ground loops. A ground loop is created when the electrical ground and the audio ground share a circuit. This creates a loop. In the JD7, we eliminate the ground loop by transformer isolating all of the outputs except output 1 which is the ground path. In order to preserve the most natural sound, we of course use the world's best Jensen transformers. These deliver exceptionally linear performance without artefact or distortion.

The next challenge is mixing one brand with another. Guitarists are often miffed when they discover their Fender may be out of phase with their Marshall. To solve this problem, the Radial JD7 is equipped with a series of polarity reverse switches that toggle the electrical phase so that the amps play in phase. It may be worth noting that most guitar pedals can also reverse the phase…

Finally, we decided that since pedals may be brought into the signal chain but may need to be temporarily removed to compare wet and dry signal paths, we chose to add separate effects loops on output channels 5 and 6. This way, you can bring pedals in and out by simply pushing a switch.

To Reamp is to Create!

Probably the most exciting recording processes used today is Reamping. Reamping is a process whereby you 'quietly' capture a dry track while the guitarist is recording his wet track. In other words, you record the performance while the guitarist is fresh. The guitarist does not have to sit through hours of repetition waiting for the engineer and producer to work out the sonic details. Once you have captured the magic you send him to the beach with his girlfriend. Then, you send the dry track back out to the guitar amps, add pedals and start adjusting the tone and moving the mics around until you get the sound you are looking for. Best of all, you can go back and Reamp the track later should the tone need to be tweaked.

Recording the dry track.

Reamping the dry track.

The Radial JD7 is designed for Reamping. You plug in the guitar and connect output-1 to the guitar amp. While the guitarist is having fun with his fuzz tones and flangers, you connect the direct box output from the JD7 to your recording system. You will be amazed! The dry track will not only send the notes, but you will also capture the sustaining feedback of the string. To Reamp, simply send the dry track back into the JD7 line level input, set the level and you can not fire up as many as 7 amps at the same time!

This is how many bands such as Steely Dan have recorded for years. The track sounds fresh and the tone can be adjusted at any time to fit the production. Once you start Reamping, you will never record any other way.

The Radial JD7 is a combination distribution amplifier, direct box and Reamp. As such there are a myriad of specifications that one may look at when determining suitability. The Radial JD7 incorporates 100% discrete parts, class-A circuitry and Jensen audio transformers in the guitar signal path to deliver near perfect unity gain with plenty of headroom and low noise. The fidelity of the audio and 'feel' can only truly be judged by plugging it in and closing your eyes!

Features

  • Audio circuit type : 100% discrete class-A with transformer isolation
  • Frequency Response : 20Hz ~ 20kHz (± 1dB)
  • Signal to Noise Ratio : -115dB (0dBu input)
  • Dynamic Range : 125dB (unbalanced input to unbalanced output)

Noise Floor :

  • -115dBu (direct output-1)
  • -115dBu (isolated outputs)

Maximum Input :

  • +13dBu (unbalanced ¼" instrument inputs-A & B)
  • +23dBu (balanced line-level reamping input)

Total Harmonic Distortion :

  • 0.05% @ 1k (direct output-1)
  • 0.05% @ 1k (isolated outputs)
  • 0.1% @ 1k (balanced DI mic-level output)
  • Intermodulation Distortion : 0.2% @ -20dBu
  • Input Impedance : Variable from 10k Ohms ~ 1megaOhm
  • Output Impedance : ¼" unbalanced: 10k Ohms; XLR balanced: 150 Ohms
  • Input Select : A or B selectable inputs
  • Input Pad : -8dB (input B)
  • Phase Reverse : 180° polarity reverse (isolated outputs)
  • XLR Output : Transformer isolated DI out with phase rev. & gnd lift
  • XLR Input : Balanced line-level Reamp input with gnd lift
  • Ground Lift : Isolated channels 2 thru 6; Bal XLR I/O
  • XLR Configuration : AES standard (pin-2 hot)
  • Power : +15VDC/400mA adapter included
  • Construction : 14 gauge steel chassis & outer shell
  • Finish : Durable powder coat
  • Size (L x W x H) : 17.5" x 6" x 1.75" (44.5cm x 15.25cm x 4.45cm)
  • Conditions : For use in dry locations only between 5°C and 40°C
SKU RAD-JD7
Brand Radial
Weight 8.7000
Dimensions (WxHxD) No

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