Here's the decoding chart as listed in the manual:
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| HDCD | 16 | 18 | 20 | 22 | 24 | None |
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| off | off | off | off | on | on | on |
| off | off | on | on | off | off | on |
| off | on | off | on | off | on | off |
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Assuming you are beginning with all LEDs off, the sequence offered previously differs from the above chart, with "None" and "HDCD" being reversed.
Apparently, the "HDCD" setting performs jitter reduction, but not Resolution Enhancement or dithering to a fixed word length. According to Robert Harley, with the unit set to "None", the DTI PRO 32 "turns off the dither, but performs Resolution Enhancement. The output word length in this no-dither mode changes with the program source, with the algorithm deciding how many additional bits it can reliably interpolate."
If this is true, then the PRO 32 performs three different functions in various combinations: 1) Jitter reduction, 2) Resolution enhancement by interpolation, with output word length variable depending on source material, and 3) Dithering to a fixed word length.
So that you don't think anything is wrong with your unit:
"NOTE that if you have selected the HDCD position, the phase switch will be disabled and both of the PHASE LEDs will be on, assuring correct decoding of these discs by a properly equipped DAC."
Also, the relay you hear click about 30 seconds after "SECONDARY LOCK" is aquired, is the jitter filter switching to "5 Hz mode".