Secrets Q & A

TVs? We Don't Need no Stinking TVs - Third-Generation Multi-channel Audio - Part 3


Conclusions - Third Generation Multi-channel Audio

When HDMI 1.1 arrived I had dreams of HDMI processor loops on AVRs, dreams of HDMI inputs and outputs on external signal processors, and dreams of power amps with HDMI receivers. Enough time has passed for me to conclude these will remain dreams and thus unlike the two-channel world, external jitter suppression and external DAC units are not feasible. Given this the performance of the DACs and analog circuits after the DACs of your AVR will limit the performance of your system. Most product information for AVRs gives almost no indication of the units performance from the DAC on out. Sometimes they provide the part number of the DAC but that is about it. Maybe a crumb of information about the ASRC being used. Only a service manual will provide the information you want about the built quality but service manuals for AVRs can cost of over $100. Smaller companies will not provide a service manual at any price.

Even with a service manual you will not be able to verify if anything is wrong with the code in the DSP used to implement the DSD transcoder, reconstruction filters or a soft ASRC. On the other hand Dolby and DTS codec performance must be verified before they will approve the AVRs for sale.

What you really need are independent measurements of the AVRs you are considering from HDMI in to analog out. Unfortunately very few magazines and webzines are measuring AVRs in this ways. Most just measure analog in to power amp out. Measurement from the HDMI in impossible without extremely expensive test equipment (HDMI encoders require licenses from Dolby and DTS). Only one print magazine has this equipment. Absent this equipment only the stereo channels can be tested using S/PDIF which prevents making some key tests. Even under this restriction the magazines have found significant design problems ranging from poor DAC linearity even at the 16 bit level to significant frequency response errors when presented with 96kHz LPCM data. I would not recommend spending over $1000 on an AVR without a complete test report at least using the S/PDIF port.


Very useful three-part essay
Written by Howard Ferstler , June 28, 2011

Dr. David Rich is one of the more knowledgeable audio researchers in the business today. This third part of his three-part article wraps things up nicely. I really cannot think of any other articles I have read on the multi-topic issues here that have been covered more comprehensively.

I believe that serious multi-channel audio is going to have problems gaining ground in today's marketplace, simply because (allowing for the also problematic economic downturn) many, if not most, of those who listen to music on A/V or audio-only systems do so without paying much attention to accurate reproduction, either by the speakers or by the processing hardware. However, some do, and Dr. Rich's analysis will be very useful to this latter group.


Multi Channel Grammar :)
Written by Scott , July 08, 2011

The content is great, but the editor needs to step up quality control regarding the technical aspects of the actual writing. Again, the content is nice and I love this site, but as a teacher I see too many things slipping these days. Please continue to publish thoughtful and well written articles! Cheers!


Answered A Lot of My Questions
Written by Dave J , July 17, 2011

This article pretty much coincides with my observations. In the years that multi-channel audio was available, I saw almost nobody pursuing it. Further more, in the many homes that I've been in, I don't see many basic home theater surround sound systems _ never mind elaborate ones. The other thing that I suspect is keeping multi-channel audio from catching on is people like me. I'm one of the many who listens to LOTS of content off the internet and [if allowed to] "archives" it for use with portable audio. Multi-channel audio is of no use to me, because _ in this case _ I am using headphones.


    Written by Common Sense , August 11, 2011

    I ripped by 57 DVD-Audio discs to my computer hard drive using DVDAExplorer. I use foobar 2000 for flawless playback. No Oppo required.

    A htpc is superior in every way like the 3TB drive i use to stream audio and video files to anywhere in the house using a simple network drive mount.

    Or a another use as a OTA DVR with Windows media center 7. No subscription required for our still free public airways.


    Written by Alex Theodore , September 09, 2011

    Thank you for these 3 articles so instructive.

    Would you answer my question?

    As you did and do for Hdmi Output in the video area, why you don't test the accuracy of this output (Hdmi) in sound area (like LPCM, DD-HD bitstream ...) ?

    thank you


    Written by JJ , September 12, 2011

    Thanks for making me go through the articles again to find typos. I made further corrections that I had initially missed. These were very intense manuscripts to edit.