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JDV™ FAQ

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Can I power the JDV with 48V phantom power?

No. Typical 48V phantom power only has 5 milliamps of available current. The JDV requires much more current than this to drive the class-A circuit and produce the amazing headroom.

What makes the JDV better than other active direct boxes?

Sound quality. There is nothing on the planet that will do a better job than the JDV. It is designed from the ground up to be sonically pure, exceptionally dynamic and totally transparent. The combination feed-forward design, class-A circuit and 30 volt internal rails combine to put the JDV in a class of its own.

Why is Class-A considered best?

Golden ear audiophiles have always preferred the sound of class-A amplifiers with full size discrete parts. These employ a single gain stage as opposed to class-AB amplifiers that separate the signal into two half waves, amplify them and then bring them back together. Class-A amps are simple, less efficient but do not suffer from zero-cross distortion.

What is zero-cross distortion?

When class-AB amplifiers bring the two half-waves back together, these have to be perfectly aligned at the zero-cross point so that all frequencies are faithfully amplified. Aligning upper harmonics – from 5Hz to 20,000Hz is exceedingly difficult, if not impossible. The advantage to class-AB amps is that they are much more efficient. But with the JDV, we do not care about efficiency, we are only concerned about producing the utmost audio quality.

Can you explain negative feedback?

In audio, negative feedback is used to stabilize the amplifier to prevent run-away. This is the first thing they teach you in electronics-101. But when you take a positive and mix it with a negative, the result will be phase cancellation. Electronic engineers have always compromised by attempting to keep negative feedback at a minimum. The JDV is completely void of negative feedback.

Why are feedback loops bad?

Feedback loops and class-AB amplifiers are not bad - they are in fact very good. These technical advancements are part of every day audio and we employ both in many products. The JDV is very special in that it avoids the use of both in preference to delivering superlative audio.

Does the JDV employ transformer isolation?

No. The JDV is a 100% discrete device with a transformerless signal path. Although transformers are absolutely wonderful devices and we use tons of them, they introduce a personality to the audio signal path. The JDV targets the user that is obsessed with retaining the audio integrity of their instrument and therefore, decided to avoid any parts that could potentially alter the tone.

How will Drag Control affect active instruments?

Active basses or acoustic guitars with built-in electronics have internal buffers that basically amplify the signal before it reaches the JDV. Drag control will not have any effect on pre-buffered signals.

Can I overload the JDV’s input?

Probably not. We could only get the JDV input to overload when we drove the output from a mixer directly into the JDV and turned the volume up high. It is unlikely, under normal use, that you will ever overload the JDV.

Can I connect a guitar amplifier to the JDV?

You can; however there are more suitable products such as the Radial JDX that are designed to do this. The JDV is equipped with a secondary -30dB pad that is designed to be connected via the speaker cabinet output – not the head. In other words, you need to load the amplifier with a speaker so that the JDV does not blow up. Most speaker cabinets are equipped with parallel ¼” connectors. The JDV will only tap a very small portion of the signal and will not alter the load on the head.

What level is a unity gain device?

Amplifiers come in all types and sizes. Some such as the ones used in PA systems are designed to produce tremendous power increases to drive loudspeakers. Others such as guitar signal buffers or direct boxes are designed to simply pass the signal along without increasing the level. These are commonly known as buffers. The JDV is a unity gain device. What you put in will come out.

Why is the PAD on the output?

The JDV is designed to handle any type of signal level without distortion. This means that if you put in a very loud device such as a keyboard or active bass, it could overload the receiving device. A good example would be the mic splitting transformer or active circuit in a snake system. These are designed to handle mic levels… and because the JDV’s output can be significantly higher depending on what input it receives, it will simply pass it along. By having the pad on the output, you can reduce the level to protect other gear from overload distortion.

Why does the JDV use an external power supply?

There are several advantages to using an external supply. First, by keeping the power transformer outside the protective metal casing, this avoids electro-magnetic induction which could pollute the sensitive circuitry. Keep in mind the JDV has 4 mOhm input impedance; this is particularly sensitive to noise. Second, the most common point of failure with electronic equipment is the power supply. An external supply can easily be switched out for field service. Finally, by changing the power supply input voltage and cable, we can ship products around the world and meet all of the safety standards.

Can I use the tuner out to drive another amp of effect device?

Yes.

Why did you not put a knob on the Drag control?

Drag Control is usually set once and the left alone. We therefore decided that it should be a set & forget arrangement.

Can I use the JDV as a Reamper?

The JDV is not designed for Reamping. We suggest you use one of our Reamp boxes such as the Radial X-Amp® or Reamp® JCR to achieve the best sound quality when Reamping in the studio.

What are the differences between the first generation Radial JDV and the current model?

Both employ John Vrtacic’s original circuit design. The first model employed a rechargeable battery pack as a means to avoid a power supply. When we decided to update the design, we also chose to add a bunch of new features such as enhanced connectivity, Drag Control and filters.

How does the JDV compare to the J48?

Both are active. The JDV is for the ultimate purist, while the J48 is designed for general use in professional studios and live touring. The JDV needs to be plugged in while the J48 gets its power from 48V phantom. The J48 is as good as it gets considering the limited current available from phantom power.

Can 48V phantom power harm the JDV?

No. The JDV is equipped with blocking capacitors to protect it from the 48V DC>

I have an old JDV with a built-in battery pack. Do you have any documentation on this item such as a user manual available?

Yes. Simply Click here to download the PDF.

Which active DI box would you recommend for recording an Archtop Guitar with stock Gibson humbuckers?

As magnetic pickups react to the input impedance, the best choice would be a Radial DI that is equipped with Drag control. Options includes the Firefly Tube direct, the JDV class-A direct and several others.