• Registered: 2020-10-14
  • Posts: 3

Topic: Turning on ADI-2 DAC FS trips amp protection circuit

I have an ADI-2 FS in the following chain:

Bluesound Node 2i > ADI-2 DAC FS > Pass Labs INT-25. If I turn on the amp before the ADI-2 it often trips a protection circuit in the amp so that I have to turn the amp on and off again for it to work. Recently I had to send my amp back to Pass because it died completely and this may have been the culprit.

I have the following settings on the ADI-2:

- Volume is locked at -5db
- Reference level is +7 dbu

This is using RCA connections.

Is the problem that the ADI-2 is sending some voltage spike when turned on? Pass Labs indicated this might be the case. I’m concerned this might keep causing damage.

This is from Pass:

“ A guess, but very high probability.  The output device in the INT-25 has a protection circuit.  If there is any oddness at the input of the amp  (most commonly DC voltages, or very high frequency noise  coming across the RCA cable,) the protection circuit shuts off the bias to the output device.  When this happens, gain drops dramatically and distortion climbs astronomically”.

Any help is greatly appreciated. My amp is a 50 pound beast so sending it in for repairs is no fun!

  • KaiS
  • DAW Mastermind
  • Offline
  • From: Germany
  • Registered: 2020-02-05
  • Posts: 3,525

Re: Turning on ADI-2 DAC FS trips amp protection circuit

It‘s always a good practice to switch on the power amp last, after all other devices.
At least turn the power amp’s volume down.

To check your ADI-2 for DC, bring down the INT 25’s volume to a safe level, closely watch your speaker’s woofers and turn on ADI-2.
The woofers shouldn’t visibly move, and no pop- or other switching-noise should be audible.

Finally: an amp that breaks when overloaded is misconstructed - sorry to say.

KaiS's Website