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J+4™ FAQ

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Can the J+4 drive a power amp from a CD player or I-Pod?

Yes. The J+4's -10dB input and +15dB output capacity will provide plenty of signal to drive a power amplifier.

Can I use a guitar with the J+4 to drive a power amp?

No. The output level from a guitar would be too low to drive an amp directly. You would have to increase the level of the guitar using a preamp first.

Can I use a hi-Z mic with the J+4 to drive a power amp?

No. The output level from a microphone would be too low to drive a power amp. You would have to increase the level of the mic using a preamp first.

How long of an XLR cable can I connect to the Radial J+4 to drive a distant amplifier?

The normal maximum we recommend is 100 meters (300 feet). You can extend this but will likely begin to hear noise creep into the system and a loss of high frequency response.

Can I use the J+4 to reduce the level from a -10dB line level device to feed a mic input?

Yes, this will work but you are not really gaining anything as you will not be using the buffering amp inside the J+4. There may be other more suitable devices such as using a passive stereo DI like the ProAV2 which could do this at a lower price.

Can I use the J+4 as a line isolator to eliminate noise?

Yes. The transformers inside the J+4 will help eliminate hum & buzz caused by ground loops and will provide plenty of headroom for +10dB line isolation. if you intend to isolate high level devices like a concert mixing console, the Radial TwinIso may be a better choice as it can handle in excess of 25dB.

Can I connect a device to the RCA inputs and then use the ¼" inputs as outputs to feed a second device like a thru-put?

This could work but you could encounter noise as there is no way to isolate the two devices. Best solution here would be to test in advance as the equipment being connected will dictate how well this would work.

Can I connect an iPod or computer to the Radial J+4 to drive a PA system?

Yes. By running the iPod directly into the balanced +4dB line level of a mixer, you will likely encounter less noise. This will be particularly noticeable when connecting a power supply to the source such as a computer. These are often a major source of system noise. The isolation transformers and buffering amplifier combine to eliminate stray AC and DC currents from running around the audio system.

Can I use the radial J+4 backwards like a passive DI box?

No. The buffering circuit inside the J+4 will block audio from coming into the unit via the XLR output connectors.

Can I use 48V phantom power to supply the needed voltage to the Radial J+4?

No. The J+4 is designed to deliver a proper line level output. To do this, it requires 15 volts with 400 milliamps of current. Phantom power only generates 5 milliamps of current which would not be sufficient to run the J+4.

Will 48V Phantom power harm the Radial J+4?

No. The J+4 is equipped with blocking capacitors to prevent DC from harming the circuitry.

Can I use a battery to supply the needed voltage to the Radial J+4?

No. The J+4 is designed to deliver a proper line level signal output. To do this, it requires 15 volts with 400 milliamps of current. This type of power draw would run a battery dead in minutes.

Can I connect a keyboard or digital piano to the J+4 to drive a power amp?

Yes. The line level output from a self-powered keyboard is usually plenty to drive the input stage of the Radial J+4.

Can I use the Radial J+4 to drive an extra set of studio monitors?

Sure! So long as you use a -10dB line level signal from your mixer or sound card, you should have plenty of gain to drive your system.

Can the Radial J+4 drive headphones?

No, not unless they are powered. You really need a headphone amplifier for this task.

Why did Radial use a 'wall wart' to power the J+4?

No one likes wall warts, but the only way to supply a product to global customers while keeping pricing down is to use external power supplies. This allows Radial to conform to all of the various international power safety regulations so that Radial products can be used safely around the world. Add to that another advantage—wall warts take the power transformer out of the box, eliminating 60Hz hum.

Can I use the Radial J+4 as a preamp for recording?

Absolutely. The Radial +J+4 is in fact a line level preamp and it is extremely quiet. This makes it ideal for running devices such as keyboards into balanced line level systems.

What do I do if I hear distortion?

Check first to make sure you are not overloading the line level input device with the Radial J+4. If this is not 'in the red', then turn the input source device down and increase the output level from the Radial J+4 to provide gain make-up.

Can I run a turntable into the Radial J+4?

A turntable first needs an RIAA preamp before you can increase the level. The Radial J33 would likely be a better choice for this application.