HDCD stands for High Definition Compatible Digital and was developed by Pacific Microsonics, a company acquired by Microsoft in 2000. HDCD encodes the signal on a standard CD in such a way that when decoded it has extended dynamic range and supposedly lower distortion – it is claimed to provide the near-equivalent to 20 bit audio despite the fact that CD is 16-bit.

The snag with HDCD is that not all players decode it. The idea is that HDCD is relatively benign in this respect, and HDCD-encoded CDs still sound good when played back without decoding.

Now audio engineer Steve Hoffman, who specialises in remastering classic CDs for maximum fidelity, says that HDCD actually makes CDs sound worse:

It degrades the sound and it bugs me. I’ve tried everything, every way and it just diminishes the fidelity.

Stephen Marsh, of Stephen Marsh Mastering, who works with Hoffman, adds:

In the interest of giving the HDCD system the fairest of all shakes, I again today ran our completed Bad Co. master through it D to D in 2 additional configurations. First I took our fully prepped, edited 24 bit/44.1 out of converter aes through the HDCD box, outputting 16/44.1 HDCD. Second – I took our 24/88.2 captures and ran those through the box to 16/44.1 HDCD. In both instances we found the HDCD box to be at least as detrimental to the sound as we heard while A to D’ing with it Friday – if not more! In particular – I listened to the HDCD encoded material in un-decoded fashion so I could get a sense of what most consumers are going to hear. Even through the best converters in the room the results were very unsettling: Namely – there was a dip at around 8K the took all the snap and sparkle out of the snare and deflated the air out of the tracks. Engaging the decoding circuits and monitoring through the HDCD D to A’s lent an overall ‘generic’ feel to the sound – it sounded fine, don’t get me wrong – but it didn’t sound special and was certainly not an improvement.

The HDCD concept has always bothered me as well. It is fixing a problem that does not need fixing: neither distortion, nor dynamic range is an issue with standard 16/44 CDs. The fact that not all CDs will be decoded correctly is a worry. Finally, any processing risks degrading the sound, and other things being equal the straightest path is the best.

I recall discovering back in the days of compact cassette that recording and playback with Dolby switched off generally sounded best, even though tape hiss on a cassette was a real problem that did need fixing.

Even if Hoffman and Marsh are wrong, and HDCD does sound better when properly decoded, the fact that it often is not properly decoded is good reason to steer clear.

Now that CDs are commonly ripped to a music server HDCD encoding is still problematic. Illustrate’s dBpoweramp has a decoder that creates a 24-bit file from HDCD-encoded CDs.