Passive DI Box Design

[smilan]

Hi,
I have a Jensen JT-DB-E transformer and I would like to build a passive DI box.
The Jensen data sheet present this circuit with a 6K8 resistor between the input jack to the primary side of the transformer and a 51R resistor in series with a 10 nF capacitor that connects pin 1 of the output XLR jack to ground that is active when the ground lift is active.
What are the advantages of this circuit over more simple circuit with no resistors and capacitors?

 

[JohnRoberts]

The Jensen advice is usually pretty solid.

JR

 

[Ike Zimbel]

What John said. The cap and resistor in the ground lift circuit is designed to shunt RF and other noise to ground while still "lifting" the connection to ground.

 

[abbey road d enfer]

Hi,
I have a Jensen JT-DB-E transformer and I would like to build a passive DI box.
The Jensen data sheet present this circuit with a 6K8 resistor between the input jack to the primary side of the transformer and a 51R resistor in series with a 10 nF capacitor that connects pin 1 of the output XLR jack to ground that is active when the ground lift is active.
What are the advantages of this circuit over more simple circuit with no resistors and capacitors?

The 6.81k is there for protecting the primary against possible DC, e.g. when connecting to an active guitar, and provides a degree of RF protection; the resistor and the xfmr's stray capacitance form a low-pass filter.