1 Topic by maartenl (edited by maartenl 2026-03-30 17:25:26)

  • Registered: 2019-04-25
  • Posts: 37

Topic: Autoref vol ADI-2 DAC FS: strange behaviour?

When adjusting volume on my ADI-2 DAC FS (AK4490 version, FPGA 81, DSP 62) with XLR output and auto ref on, following happens as outlined below. dBu and dBr levels as displayed by the dac. Equalizer is disabled.

volume upwards (louder)
-21 dBr: -5 dBu > +1dBu
-12 dBr: +1 dBu > +7 dBu
-6 dBr: 7 dBu > +13 dBu
volume downwards (less louder)
-6 dBr: +13 dBu > +7 dBu
-12 dBr: +7 dBu > +1 dBu
-22 dBr: +1 dBu > -5 dBu

I have two questions:
1. Why does dBu level -5 dBU not change at -18 dBr as one would expect?
2. Why does dBu level -5 dBU change at different dBr levels (-21 dBr vs -22 dBr) dependent on when one turns the volume up or down?

  • N00b
  • N00b
  • MADI hero
  • Offline
  • From: Near Paris, France
  • Registered: 2018-10-03
  • Posts: 465

Re: Autoref vol ADI-2 DAC FS: strange behaviour?

Hi there! Do you have Bass or Treble at 0? Dynamic loudness off?

FYI, with XLR output, the output levels are +1 dBu / +7 dBu  / +13 dBu / +19 dBu (you add 6 dB to the unbalanced values).

Here are the thresholds if everything else is at 0 dB.

https://rehost.diberie.com/Picture/Get/f/502942

And for your second question, that’s normal — I think there’s a small safety margin applied when the volume is increased.

ADI-2 DAC (with stock PSU) - Neumann KH 310 A monitors - Cheap USB and XLR cables

N00b's Website

  • Registered: 2019-04-25
  • Posts: 37

Re: Autoref vol ADI-2 DAC FS: strange behaviour?

Hi N00b,

Thanks for your reply. I have not set B/T. I have enabled dynamic loudness.

I know the output levels are +6 dBu higher for balanced output, however the DAC displays the levels corresponding to unbalanced/rca output regardless which output (balanced XLR vs unblanced RCA) is being used (as per user manual).

Have checked the loudness. Turning loudness off, makes DAC-2 switch output stage at -18,0 dBr (as expected).

Now I know what makes the change. :-)

Maarten