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JDV-Pre™ FAQ

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How does the JDV-Pre compare with original JDV?
The JDV-Pre retains the original feed-forward class-A circuit in the front end that has made the JDV one of the most respected direct boxes in the industry. Where the JDV-Pre differs is that it is equipped with a microphone input, variable high-pass filter and a professional +4dB line level output. It of course is equipped with a different set of connections to address the 500 series format.

What is a feedback loop?
Audio circuits use negative feedback to stabilize the amplification stage. Without negative feedback, the amplifier could run away somewhat like a microphone can feedback and squeal uncontrollably. Negative feedback is reintroduced into the signal path to keep things stable. The problem is that when negative signals are mixed with positive signals, there will be a certain degree of cancellation. The JDV-Pre does not use negative feedback at the input stage. Less cancellation = more natural tone.

Does any other company have a circuit like the JDV?
Not that we are aware of. For years, Rupert Neve often commented that the best sounding circuits would have no negative feedback. He never actually found the way to do this. John Vrtacic – the originator of the JDV did. As far as we know, this is an exclusive..

Can I use the JDV-Pre as a direct box?
Yes. The JDV-Pre's Omniport output is a low-Z direct box output that is perfectly suited to drive signals from a stage, through the mic splitters and so on, just like a regular direct box.

What is the difference between PowerPre and JDV-Pre?
These are both preamps. The PowerPre is optimized for microphones while the JDV-Pre is optimized for instruments. Both have their characteristics and both sound terrific in their own right!

How does the Radial PZ-Pre compare to the JDV-Pre?
The PZ-Pre is a pedal that is optimized for live performance with selectable inputs, notch-filtering and muting for on stage tuning while the JDV-Pre is all about recording. It is also self powered and put inside an ultra compact enclosure.

Can you explain Drag Control™?
When a guitar connects directly to an amplifier, the amplifier introduces a load on the pickup. When the load is not properly matched to the instrument, the sound changes; the level changes; and ultimately, the feel changes. When a buffer is put between the instrument and the amplifier, the load from the amplifier is no longer being applied. Drag Control basically allows you to reintroduce the load so that the instrument sounds right.

Does Drag Control work on all instrument pickups?
No. Drag Control is primarily intended for passive magnetic pickups. If you apply Drag on a piezo, it will lower the impedance to the point where the pickup will no longer perform correctly and sound bad. Drag has no effect on active pickups as the buffering stage is inside the instrument.

Will Drag Control affect the mic input?
Yes. We suggest that the Drag Control be left in the out position and then once you have set the signal level, try testing to listen to the effect.

Can I bypass the high-pass filter?
When you turn the control completely counterclockwise, the filter is so low that it is no longer audible. But technically it is still on. The bass roll-off starts at around 5Hz which is well below the human hearing threshold.

What is the benefit of a variable high-pass filter?
High pass filters are exactly that – when applied they cut the bass to allow the high frequencies to pass. High pass filters are basically a secret weapon that can help tremendously both when recording in the studio and when playing a live performance. Bass introduces two fundamental problems: First, because bass contains so much more energy than high frequencies, it makes the amplifier work much harder. By cutting unwanted bass, you will significantly increase the amp's dynamic handling and lower distortion. Second, when layering instruments, the bass resonance from each instrument can interfere with the other. Eliminating problem frequencies makes it much easier to mix instruments together.

Can you explain why distortion can cause feedback?
When you play electric guitar with distortion, it is easier to create sustain and have fun with feedback. The same applies with acoustic instruments. When the signal is distorted, feedback sets in more quickly.

Can I use the Aux out for a tuner?
Yes. The Auxiliary output is separately buffered and transformer isolated to help eliminate hum and buzz caused by ground loops. You can use this to feed and amplifier, effects or even a tuner.

Can I connect the output of a guitar amp to the JDV-Pre?
No. The input stage is not suited for high output devices. The Radial JDX is designed to be used with an amp head in conjunction with a speaker cabinet or load box.