• From: Italy
  • Registered: 2019-01-31
  • Posts: 14

Topic: ADI-2 pro output reference levels

I use the adi-2 pro fs (with the last firmware) to execute rooms and devices measurements with REW program on a Mac book pro.
I’ve a question about the output levels.

With an input via USB of a pure sine tone at 1KHz, 0dbfs, the volume set to 0dB, I read from Adi’s TS output with my rms multimeter:

Ref level 4dbu: 1.23v
Ref level 13dbu: 2.85v
Ref level 19dbu: 5.00v
Ref level 24dbu: 5.22v

Theoretically speaking, they should be respectively: 1.23v (aligned), 3.45v, 6.90v, 12.27v (these are not aligned).
Which is the rationale about this divergence?

I noted also that connecting in loopback the outputs to the inputs via a TRS cable, setting the input ref level to 24dbu, I observe as ADC result:

- if the output ref level is 4dbu: the sine, plus some minor harmonics (The correct result).
- if the output ref level is 13, 19 or 24dbu: the sine plus a lot of high level harmonics, quite similar to the square wave spectrum. I return to see the normal sine spectrum only reducing the input level to -3.6db, for any input ref level.

Is this a normal behavior?

Best Regards,
Pino

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,844

Re: ADI-2 pro output reference levels

You have to make sure EQ and other FX are disabled at the ADI, or you will run into overload situations with such a test.

The TS output does not follow the 24 dBu setting, as explained in the manual.

Otherwise this is of course NOT normal behaviour, in a loopback the TS output should act as expected. Also if you set the same ref level on input and output it should always be between -0.2 dBFS and 0 dBFS on the input level meter.

Regards
Matthias Carstens
RME

MC's Website

  • From: Italy
  • Registered: 2019-01-31
  • Posts: 14

Re: ADI-2 pro output reference levels

Thanks Matthias for your prompt answer.

I’ve checked, any FX or EQ is disabled.
If I measure with the rms multimeter the XLR outputs, I’ve the right Volt values (1.2, 3.4, 6.9, 12.7 volt at 4, 13, 19, 24 dbu, 0dbfs, volume at 0).
But I still see some distortion (less) in the negative half wave in REW oscilloscope.

With TS loopback I read on ADI display the same levels for input and output only with both ref levels set at 4dbu.
Selecting 13 or 19dbu on both ref levels, there are some dB of difference, at least at 0dB as volume. I’ve to reduce the input of some dB the volume to see the same levels.

Thus, it should be a problem in the output stage.
Regards,
Pino

4 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 24,844

Re: ADI-2 pro output reference levels

Yes, most probably a mute transistor is shorted, generating a constant load on the output driver opamp. That will need repair.

Regards
Matthias Carstens
RME

MC's Website