Monday, May 8, 2017

The HDCD Boost

I now have clear test evidence that my Denon DVD-9000 (which is, btw, an incredible sounding machine, might even overtake my current king Onkyo RDV-1) implements the (in)famous HDCD +6dB boost.  I haven't checked the menu, perhaps there's a way to disable this (not that I'd necessarily want to though) but I don't think many other later machines even offer such a choice.

When the Denon plays back an HDCD with the 6dB boost, it will output up to 6dB higher voltage on the output, which I believe means about 4v RMS.  I didn't measure the voltage as such, I'm reading dB on digital meters downstream, with the analog to digital sampling done by my Lavry AD10 set to reference level -9dB (which is 4dB higher than the maximum gain, -13dB, which is suited for 2V, but I sorta knew and sometimes remembered was insufficient for HDCD's and perhaps DVD-Audio's, well now I now for sure that -9dB is the highest level setting on the Lavry when playing HDCD's on the Denon).

I recall a friend of mine thought that if 6dB higher level was such a good idea, that should be incorporated into normal CD playback.  It's certainly a potentially divisive competitive issue.  I could imagine HDCD standards recommending a 6dB boost over conventional CD playback on the grounds that it's really only "uncompressing" peaks that the producer might otherwise choose to compress.  But on the other hand competing standard groups insisting this boost is unfair if they don't have it also.

In my own mind I'm still undecided on that it's a pretty moot point anyway, at least for some people interested only in selling new things and services.  I have lots of HDCD's and cherish them and cherish the HDCD playback on my Denon 9000.

One of the very valid criticisms of HDCD is that it is not truly "compatible" if the boost feature is used.  The CD playback will not have those boosts, and will therefore have inferior dynamic range to what it could have if truly compatible.  HDCD got a scathing review in Audio Magazine, my cherished resource of the time, and when I read that it was enough for me.  No HDCD I decided (not that I cared much then anyway...I was in poverty then and cherishing my aged and irreplaceable Sony 507ES player).  Only a year or so a non-audiophile friend of mine was raving about how wonderful HDCD was, and I believed him, and endless HDCD listening later, I still think HDCD is great, probably better overall than SACD and close to MQA.

Anyway, in a system like mine I must know the exact level settings required for every source, for which the numbers below are a first pass:

HDCD, Denon DVD-9000: -9
CD, all players: -13 (maximum gain, I'd go to -15 perhaps if that were available)

The Onkyo RDV-1 doesn't do HDCD.  Notably Denon uses an Apogee clock, Apogee was a sort of competitor of Pacific Microsonics.

I measured the two players using HDCD and non-HDCD disk seeming to have maximum loudness (digital peak levels, measured on Behringer DEQ):

Reference Recordings RR-82CD, Track 9
Denon DVD-9000
Lavry set to -9dB
Tact set to -2.0dB
L -2.7
R -2.3

Onkyo RDV-1 (everything else the same)
L -9.1
R -8.9

The Denon is putting out 6.4dB higher level in the Left channel, 6.6dB higher level in the Right.  Most of this seems to be HDCD boost.  To be sure, I tested a non-HDCD disk, William Orbit Strange Cargo III, track 2:

L -10.5
R -9.1

L -11
R -10.7

Now, the difference is a mere 0.5dB in the left channel, but a surprising (not impossible given analog sampling) 1.6dB difference in the right channel.

Do I need a preamp to boost levels to the Lavry?  Not really, I can just toggle the Lavry switches (though that does, quickly, become a pain, I may be getting better at it).

At the -9dB setting HDCD's have very little wasted headroom, though at -13 CD's have about 2dB wasted headroom, that's not the biggest deal.

I need to test the 9000ES though.

A word about the sound.  After returning home from vacation where I had a chance to listen to another system...there is no comparison in the lifelike scale and information density.  My system playing the RRCD 82 at levels above approaches very closely the awesomeness of being front row center in symphony hall (though I suspect my reproduction levels are somewhat lower, the noise level is lower too, perhaps there's still some residual modal response boosting the bass, somehow it works to sound real).  Most other audiophile systems I have heard sound like toy victrolas by comparison.  There are few systems I have ever heard that are about as good or better.  One is the super MBL system I heard in 2014 playing low generation tapes on a UHA machine.  It had the biggest omni midrange/tweeter system MBL makes stacked on top of itself in mirror image with equally outrageous electronics.  Like mine, that system is a force of nature.


I measured the output level, and it was about 10dB too low from the output of the Sony 9000ES on Strange Cargo III, a non-HDCD CD.

This couldn't be right, I realized, not right at all.  So I hooked up the video monitor.  The remote control seems to have no "Setup" control.  Buy my programmed Harmony remote does, and from that I entered the Audio Menu.

Right on the top, there AUDIO ATT: and it was set to ON.  I changed that and immediately the level was restored to more or less the "correct" level (I am now using max gain for CD's so the numbers above aren't applicable).

and of course WOW DOES THIS MAKE A DIFFERENCE!!!  The formerly wimpy Sony CD sound is wimpy no more.  I was all wrong, this is a balsy sounding player not unlike the Denon DVD-9000.

I checked the manual the default and recommended setting is for AUDIO ATT to be OFF.   This is particularly strange in that the previous owner seemed to know a lot about this machine.

Now the CD levels of all my players are about the same, within 1-2dB or so anyway.  Previously the Sony was way off, and I had never realized how much.  I though I needed some nice preamp to boost the level.

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