Player decoding or Receiver decoding, that is the question

[welwynnick]

I've been hearing many people say two things about bitstreaming to amplifiers:

1. Onkyo owners in particular often say how bitstream to their amplifiers sounds better than LPCM over HDMI. Flawed theory is irrelevant, there are clear differences to be heard.

2. Others say that they cannot sound different, as decompression of the bitstream is lossless, and the bits are the same in both cases. If some hears a difference, it must be because levels aren't matched, etc.

My view has alway been that it depends on the way the amplifier works, and we don't know enough to say for sure. Only having a DD?DTS receiver, I was really looking forwards to hearing thes differences (or not) for myself. I recently borrowed an Onkyo PR-SC886 from very good friend, "Mad Mr H". pooling his equipment and mine, I had the following kit to play with:

Players:
Denon 3800BD
Samsung BDP1200
LG BH200
Pioneer DV989
Processors:
Lexicon MC12V4
Onkyo [FONT='Verdana','sans-serif']PR[/font]-SC886
DVDO EDGE
Amplifiers:
Sony DA9000
Magnum 125 stereo
Lynx monoblocks
Speakers:
Final electrostatics 5.1
Acoustic Energy Aegis Evo3 5.1
Acoustat hybrid electrostatics
Final, AE & Rythmik Servo Subs.
Displays:
JVC DLA-RS1X
Panasonic TH42PZ70

I figured the Onkyo would perform with BD sound tracks, but I also wanted to see how it compared with a top quality processor when playing CDs and DVDs (which was not very well). It was also a good opportunity to compare both PQ and SQ ofvarious players, using the DVDO where necessary to shore up the de-interlacing. But the focus for me was to compare player and amplifier decoding, and I looked at these combinations of tests:

PQ: Denon 3800 vs LG BH200
SQ: Denon 3800 vs LG BH200 by HDMI LPCM
SQ: 3800 into SC886 analogue vs HDMI LPCM
SQ: 3800 into SC886 LPCM vs bitstream
SQ: 3800 into SC886 analogue vs 3800 into MC12 analogue
SQ: 3800 into SC886 HDMI vs BH200 into MC12 DTS spdif

I used a Radio Shack analogue sound level meter to set the speaker levels, and an Eye One Display LT to calibrate the displays as far as I could. This is what I found. With bitstream, it was like listening to a different soundtrack. All the sounds were there, the frequencies and the dynamics etc, but with LPCM the 886 was seemingly throwing all these high resolution sounds at you without making sense or order out of them. The Lexicon seemed to know how to organise the music it was reproducing and make it convincing, but it didn't have HBR capability.

With bitstream into the 886, everything seemed to come to life. The sounds were the same, but it was like it was happening in front of you, instead of being an accurate reproduction. A wall of sound became a room full of tangiable sources.

I guess I could be deluding myself, but I don't think theres any question about it to my mind, its hardly difficult to spot. When I first put on an LPCM blu-ray thinking it was TrueHD, I come away with what I thought was a null result, and I was happy just to have the answer that I wanted. It wouldn't have stopped my getting an amp or processor with HBR decoding, I just wouldn't have cared so much. Not any more.

This is quite a revelation, and the 886 is sounding fine. In subective terms its up with the best stereo systems that I remember so fondly, its that good. Its left any DD/DTS based system behind in my opinion. My goodness, I've got to go and listen to all my BDs again. Heck, why did I bother buying all those cheap HD DVDs with their infernal dolby digital plus soundtracks? Damn. This is the most exciting day I've had for -er- yonks.

At first I thought I wasn't yet hearing everything that was on the disc. Well, I think I made a big step in that direction. I have no doubt that I could spot this reliably with blind testing, and will see if I can sort something out. However, this clearly show to me that all those people who insisted that they heard better audio from bitstream were not imagining it. In many cases it could be that they were simply listening to the film at higher volume, and I had to frop the volume down about 3 dB to compensate for what the amplifier was doing with bitstream (which I thought wa a bit of a cheat).

But no, the answer is clearly that bitstream does make a difference with the equipment that I was using. of course it could be that a different receiver or processor would have different processes when decoding and converting bitstream, and the result could be quite different. For example, the Onkyo suffers from moderate jitter over HDMI in the recent HiFi New & record Review tests, and recent Pioneer receivers were much less sensitive. It could be that they would not show an audible improvement in going to bitstream - it would be useful to get some feedback there. Furthermore the Denon 3800 seemed to suffer less with LPCM output than the LG BH200, so I have to assume that it has a better engineered and less jittery or noisy LPCM output. So I think the answer does depend on the equipment being used, but in simple terms it is clear that bitstream is better.

regards, Nick