The original Radial JDI (1996)

The original Radial JDI (1996)



Primary winding transfers prevent DC noise from passing through

The primary winding transfers the audio signal to the secondary via the inductive magnetic bridge. Only AC (audio) can pass, DC noise cannot cross the magnetic bridge.

Problem: Ground loop creates DC hum and buzz

Problem: ground loop creates
DC hum and buzz.

Solved: transformer isolation eliminates DC noise

Solved: Transformer isolation disconnects the 'hard wire' electrical input from the output while allowing the audio signal to pass. Ground loops are eliminated.

ProDI™ Development

When the Radial JDI was introduced in 1996, it revolutionized many preconceived concepts of what a direct box is and how a passive DI can often be a better choice than its active counterpart. In 2001, the JDI was redesigned to improve manufacturing efficiency which also allowed us to lower the price.

In 2002, the decision was made to produce a lower priced direct box that would enable the average musician to afford Radial quality. Company president Peter Janis explains: "At that point in time, Radial DI boxes were only used by top touring professionals. But we were getting requests to deliver a product that the average music store could supply. So we approached Jensen and asked them to build us a lower priced transformer that would enable us to produce a DI box that could sell for $99. Jensen told us that in order for them to attain the quality that has made them famous, there was simply no way they could do it. As an alternative, we had a custom transformer made and this is now used in a variety of Radial products."

The Jensen transformer is as good as it gets. It is ruler flat from 10Hz to 40kHz, is able to withstand tremendous signal levels while retaining amazing phase coherence at all frequencies. The Radial version comes close with a ruler flat response that spans for 20Hz to 18.5kHz. In many cases, the Radial transformer will work very well, particularly in live touring where the PA system rarely produces sound above 15kHz.

The same Radial transformer is used in the ProDI, ProD2, ProAV1, ProAV2 and the ProD8. The ProD2 is a stereo version of the ProDI, the ProAV1 and ProAV2 are similar again with a different connector set and the ProD8 is an 8 channel rack version designed for keyboards.

As for how it sounds? Well… considering it is on tour with Herbie Hancock, Rush, U2 and Lady Gaga, I guess you can say it is pretty darn good.

ProDI uses a specially made custom audio transformer
ProDI uses a specially made custom audio transformer.
JDI uses the Jensen transformer
JDI uses the Jensen transformer

Frequency Response


Phase Response