Frequently Asked Question

USB powered DAC still powered without external power?
Last Updated 2 years ago

Question: Using the iDefender 3.0 without external power and connected to a USB-powered DAC it doesn't disconnect the power as it still works?

Answer: It contains a "clapham junction" circuit, which, if the DAC draws power and external power is not connected it switches over to bus power (actually connects power & ground).

Question: So you you mean that it only disconnects power when external power supply is connected?

Answer: No.

It switches grounds (which is what matters) and +5V line to high impedance but leaves them connected (to allow DAC's that require the 5V line for "handshake) UNLESS the DAC draws significant current.

In this case it enables a bypass circuit, that is disconnected if external power is applied.

So for iDefender without external power:

  • DAC draws Ground & +5V high impedance
  • DAC draws > appx. 1mA -> Ground & +5V direct connection

For iDefender with external power:

  • Ground & +5V high impedance

The switch over is transparent and instant. This is aimed at pro audio application where a lost external power would mean a dropped recording, or a dropped set for a DJ.

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