HDCD Light
Posted by: Kevin Richardson on 03 April 2016
While listening to a 24 bit release of some of Elvis greatest hits, I noticed several of the tracks turned on my DAC's HDCD indicator light. My understanding is that this encoding is 20 bits extracted from certain CDs so I am confused why a high resolution file would cause this. Any ideas?
If it's nDAC, the light normally lights up when the signal is at 48kHZ or higher...
There was no HDCD indicator on my Naim DAC, unlike my CDX2 or the CDS3. As above, I thought the light came on above 44.!K although Adam sounds like he knows what he's talking about so I'll go with 48 too.
Quote from the nDAC manual:
The hd indicator illuminates to indicate that the input data stream is “high definition”. High definition is defined as any data stream with a sampling rate above 48kHz.
Sorry. Thought it was the Naim DAC.
Alba1320 posted:HD and HDCD are not the same thing (as links are not allowed, do a search for HDCD for info.).
From the Spec. for the Berkeley DAC that the OP is using:
HDCD decoding detects 16-bit flag at 44.1kHz or 24-bit flag at all sampling rates
So my 24 bit files were encoded with HDCD flag? I only have heard of this in the 16 bit world. It is strange since only a few tracks have this encoding.
Sounds unusual, HDCD is a special DSP method for 16bit 44.1kHz PCM files that compands the sound (opposite of compression). It approximates this expansion to 20bit dynamic range on certain pieces of material within the sampled audio.
The actual controllers of HDCD are little instructions in the least significant bits of the 16 bit PCM sample so are effectively in audible. The HDCD DSP controller detects the presence of these in the sample stream and typically you will see the HDCD indicator illuminate. Technically I see no reason why this would not work on a 24bit PCM sample, but I am aware of no mastering equipment that would create this, and I can't see that there would be any benefit sonically in doing this.
Perhaps the 24 bit sample files with the HDCD controller flags in are not true 24 bit files, but are most significant bit padded 16 bit files with a 24 bit header...do these files playback softly? Sounds strange as I say.
Simon
Simon-
That was my thinking that the files were sold as 24 bit but are just modified 16 bit files. I got the album from HDTracks so they have a decent reputation.
the overall sound level appears uniform across the HDCD and non HDCD tracks.
Well as I say it does sound strange - there are some command line utilities on the web that will parse a HDCD file and identify the commands - google is your friend if you are curious, but I remember the utilities were not easy to find... anyway if you hunt one down it might be interesting to see what operands are encoded in the 24 bit file..
Well somebody from Berkeley Audio called me this evening and explained this unusual light. He told me that the light indicates the track was mastered using certain models of ADCs made by Pacific Microsonics.
Kevin, well the two Pacific Microsonics HDCD mastering processors, the HDCD Model One and HDCD Model Two are long out of production, but are still prized assets in some studios.. I have however just downloaded the Model Two operating manual and indeed it can create HDCD masters (with the LSB instruction insertion method) using 16, 20 and 24 bit sample word lengths upto 192kHz sample rate.. The none CD sample depth and rates were originally for DVD Audio masters.. So there we go...