Tuesday, December 02, 2008

It's Been Awhile... Problems Playing Blu-ray.

For those of you who may actually read this blog, I apologize for not writing anything since June. I'm still around and hope to start posting more frequently.

We haven't made much progress lately with our product development. There are a couple of big hurdles, which we don't have a lot of control over that have slowed us down.

One of the issues that we have to deal with is multichannel audio playback of Blu-ray movies. Our product should be a pretty good match for the HD audio codecs, like DTS-HD Master Audio and Dolby TrueHD. Both provide lossless encoding of up to 8 channels of audio with a bitdepth of 24 bit and up to 192 KHz sample rate. The highest resolution will probably be 24/96 most of the time and many titles might be 24/48. With such high resolution it seems a shame to play this quality of audio with just a basic audio/video receiver. I think you'd want really high quality DACs and powerful, low distortion amps to play back this HD audio in its full glory. That's one of the reasons we think our product is a good fit for HD audio. We plan to include the highest quality DACs and amplifiers.

So here's our problem. Since our product is meant to be connected to your HTPC and will perform the duties of your soundcard, it is dependent on the movie playback software for decoding the audio streams. Currently, the most popular software for Blu-ray playback is Cyberlink's PowerDVD Ultra, ArcSoft's TotalMedia Theater, Corel's WinDVD 9 and Nero's Nero 8 Ultimate. From what I understand, none of these programs will let you play DTS-HD Master Audio or Dolby TrueHD without downsampling, unless your hardware supports a protected audio path (PAP). Basically to play Blu-ray movies with AACS copy protection using an HTPC, the hardware must have a PAP to play the original HD audio if the bitdepth and sample rate are more than 16 bit and 48 KHz. Without PAP, the HD audio has to be downsampled to 16 bit/48 KHz as per the AACS specification. The basic audio path starts with the software player, which decodes the audio from either the encoded DTS-HD Master Audio or Dolby TrueHD into multichannel LPCM (linear pulse code modulated) data. Next, the LPCM is transmitted to the DACs, which convert the LPCM digital data into analog waveforms. Finally, the analog waveforms are amplified and output to your speakers. So, the reason for AACS and the PAP is to prevent people from getting the digital data and making perfect copies of the original HD audio. The critical part of the audio path that needs to be protected is between the software player's output of LPCM and the DACs. Unfortunately, there's no hardware standard for PAP that can be used with any hardware device. You have to develop your own proprietary hardware/driver solution and get each of the software players to support it. Unfortunately, there's no industry group working on a standard either. Maybe Microsoft will provide some support and guidance with Windows 7, but I haven't read anything that gives me hope. Actually, I'd be surprised if Microsoft came up with a good solution since it seems they're not too motivated to support Blu-ray in any way. So, to say the least, I'm a little pessimistic about PAP and HD audio playback with Blu-ray movies. There are some workarounds, but it's a PITA. You can use AnyDVD HD to decrypt the Blu-ray disc, then you split the audio and video into different files, convert the lossless HD audio track into a multichannel lossless audio format like WMA lossless or FLAC, and then recombine the audio and video into a MKV file and play it back with something like Media Player Classic. Like I said, it's a pain in the ass. You also lose all the extras.

The thing that really bugs me about this is all the encrypted formats used in Blu-ray have been cracked. So the pirates have no problems getting the unencryped stream from a Blu-ray disc. Legimate owners of Blu-ray discs can't play the full resolution HD audio, but pirates can still copy it. Hopefully, the current trend toward DRM free music will carry over into the movie industry and they'll relax the PAP requirements in the future. Maybe they'll be more open to this if Blu-ray player and disc sales don't increase during this holiday season.

Monday, June 23, 2008

Denon's Amazing CAT6 Ethernet Cable

I've subscribed to a thread dedicated to advanced topics in HD audio on AVS Forum where someone brought the Denon AKDL1 Dedicated Link Cable to our attention. This is a $500 ethernet cable. Now that's outrageous. Somebody please explain to me the benefits of such a thing. Anyhow, what's really hilarious are some of the customer reviews. Here are some of my favorites:

"A caution to people buying these: if you do not follow the "directional markings" on the cables, your music will play backwards. Please check that before mentioning it in your reviews. I was disappointed. I consider myself an audiophile - I regularly spend over $1000 on cables to get the ultimate sound. I keep my music-listening room in a Faraday cage to prevent any interference that could alter my music-listening experience. Sending any signal down ordinary copper can degrade the signal considerably. While ordinary listeners might not notice, to somebody with even a rudimentary knowledge of sound, the artifacts are glaring. Denon should have used silver wiring (hermetically sealed inside the rubber sheath to prevent any tarnishing, of course), which has a significantly higher conductivity than copper. Furthermore, Denon needs to treat the wires they use in the cable with a polarity inductor to ensure minimal phase variance."
- Michael McKinley

"If I could use a rusty boxcutter to carve a new orifice in my body that's compatible with this link cable, I would already be doing it. I can just imagine the pure musical goodness that would flow through this cable into the wound and fill me completely -- like white, holy light. Holding this cable in my hands actually makes me feel that much closer to the Lord Jesus Christ. I only make $6.25/hr at Jack In The Box, but I saved up for three months so I could have this cable. It sits in a shrine I constructed next to my futon in Mother's basement. I only gave it four stars in my review because I can't find music that is worthy enough to flow through this utterly perfect interconnect."
-G. P.

"As excited as I was to open my new Denon AKDL1 Dedicated Link Cable, I was much more dissatisfied by Denon's customer service experience. Apparently the result of an improper connection and the cable's high data transfer speed, I mistakenly caused the collision of a pair of positrons (i.e. leptons) at several hundred GeV. While the resulting mini black hole theoretically proved the validity of superstring theory and may result in endless new perpetual energy sources, it also stained our Berber carpet. When I phoned Denon customer support, the representative I spoke with--whose English was horrible, by the way--was discourteous and unhelpful. Regardless of my data transfer or particle acceleration needs in the future, I will not be shopping with Denon again."
- Mark E. Putnam

"Like an idiot I didn't follow the instructions that came with the cable. Instead, I "accidentally" ground them up in a blender along with a pile of Monster cables. What came out was a green, glowing, runny substance. I wasn't sure what I could do with it, so I threw it out of house and onto the garden. What happened, no one could have expected. Apparently most of the ooze found its way onto a family of turtles. It began to physically change them. It has been two weeks now and I have four teenage turtles in my house constantly breaking things with their martial arts. I'm about out of pizza and would like Denon to explain how these seemingly flawless cables could have caused such a problem. I read all of the warnings and didn't find anything in them about not blending them up and pouring it on turtles. I would like a full refund, or at least, Denon to cover my pizza bill."
- C. Whalen

"My wife and I have been trying to conceive for almost a decade. We've tried every form of therapy, artificial insemination, and some other, more questionable methods. Then I saw this product. The Denon AKDL1 Dedicated Link Cable. I just KNEW that it was the answer to our prayers. When they arrived my wife gave me the look of a defeated woman with nothing but a feigned hope. But I had faith! That night we wrapped ourselves in the Denon AKDL1 Dedicated Link Cable and tried one last time for a child. Nine months later our daughter was born. Thank you SO MUCH Denon AKDL1 Dedicated Link Cable. I'm only giving the product a 3-star rating, however. I was hoping for a true heir and I don't feel like buying a new cable."
- Steve O

"I got these cables to pull my Audi out of the ditch with Jed' pick-up, and they broke all up on the first pull. I knows it wasn't cause he was drunk and popped the clutch, these cables jest aint no good."
- Robert Cole "Jed's friend"

Never knew Amazon's customer reviews could be such a great source of entertainment. Learn something every day...

Monday, June 16, 2008

I Messed Up My Blog

I decided to update the design of this blog. Our current blogger template has two columns with the left column taking about 75% of the screen space, which leaves 25% for the right column. I had also just added the last.fm widget because the Sonific widget doesn't work any more. Sonific's website is gone and they no longer support their widget. The last.fm widget, along with a few others I was using, align along the left side, but are located in the right column. The text and widget alignments in the right column have bothered me for a long time, so I was trying to find some way to fix it. The text in most of the lists was aligned to the right and some of the widgets would only align to the left. Anyhow, I think it was a mess.

A few days ago, I tried testing out a few new blogger templates. I wanted to see what it would look like if I used a 2 column template with the large column on the right side. Basically, just a mirror of the one I was using. So I looked at the ones that are included with Blogger and searched the web for any others I could find. I found several that looked like they could work. Many of these will let you look at a preview, but you can't really tell if they will work unless you try them with your own content. So, I backed up my template to my local computer and tried a few of these other templates. Since I had this backup, I figured nothing terrible could happen because I could simply restore and our blog would be back to what it was before these experiments. Well, I was wrong. The actual blog articles are intact, but the list that I had for links, music stores, interesting forums, articles, etc., are all gone. I'm not sure why this happened, but I think the format for these link widgets must have been different on some of the experimental templates and they wiped out the ones that I had.

Oh well, I'm going to try to reconstruct them from memory. I should have saved each URL separate from the blog, but I didn't... I'm also going to take this opportunity to redesign the blog so everything will align a little better. So it might be a little while before everything is back to normal.

Friday, June 13, 2008

HDtracks - Another Music Store with High Quality Downloads

We can now add HDtracks to our list of online music stores that offer true CD quality tracks and albums. I just discovered them a few days ago and they offer music from a wide variety of independent labels. There's an impressive list of artists, including Buddy Guy, Albert Collins, Muddy Waters, John Prine, Aaron Neville, Rahsaan Roland Kirk, Jean-Luc Ponty, Gary Burton, Norah Jones, Chuck Mangione, Patricia Barber, Judy Collins, Joan Baez, Robin Holcomb, and on and on...

You have a choice of these download file formats (in decreasing file size order) - AIFF, FLAC and 320 Kbps MP3s. And this is something the other music stores should also provide - they include a very nice PDF file with all the cover art and liner notes. Oh, and of course, all the tracks are DRM free. In the near future they will offer select tracks in high resolution 24bit/96KHz formats. Hopefully, this will include some surround recordings.

HDtracks was founded by David and Norman Chesky of the audiophile record label Chesky Records. On their 'About' page they state: "In an age when there is a computer in every home, we have grown accustomed to accessing music at the touch of a button. But, what about the quality of that music? Why should the sound suffer because of convenience? With HDtracks, we have discovered the way to have it all: world-class music, unrivaled sound, and files that play in any environment."

They have a free sampler album (there's a link on the front page of their website), so I decided to test out their download process. After registering (don't worry, it's painless), you get an email that includes a link to the freebie. I can't remember all the details because it was a few days ago, but once I clicked on the link and followed the instructions, a little download program (Java applet) started and displayed the default settings for destination folders, etc., and provided a big button to start the download. Each track was listed and a progress bar indicated that the downloads were very quick. This was for the FLAC files. Overall, I was pretty impressed. HDtracks seems to have done it right, a great selection of music and their download process was very quick and easy.

Thursday, May 22, 2008

Vista Audio Playback, Part 2

I've been pretty busy lately, so haven't had time to post any articles. Earlier today I received a nice email from someone (won't mention names unless I have permission) who's also a big HTPC proponent. He mentioned that he's been following Amplio Audio and anxiously awaits updates on our amps and our next article about Vista audio playback. Well, that was the kick in the ass I needed.

BTW, if you read an article that you would like me to follow up on, or have any questions, please feel free to use the comments at the end of the posts. I realize that most people are comfortable with email, but I'd like to see these articles become more of an open conversation that anyone can contribute to.

Anyhow, back to the topic... In the original Part 1 article I mentioned comments I read in a thread on diyAudio titled "Is Vista really capable of bit perfect output?" The original poster started by explaining that the sound quality when playing audio/music with his computer was better than using his expensive dedicated audio components. There are a couple of reasons some may believe a computer based audio system can never sound as good as dedicated stand-alone components. One is that the computer is just too electronically noisy to pass an analog signal without some distortion. The second reason is that the computer software and/or operating system modifies the audio data before passing it to the soundcard and DACs, thus distorting and/or damaging the sound quality.

There are several ways to avoid the first problem. One is to purchase a good quality soundcard that is properly shielded from any electro-magnetic interference. The other is to use a product who's analog circuitry is external to the PC. All FireWire and USB based soundcards fall under this category, as do a new generation of USB DACs. The product Amplio Audio is working on falls under this category as well. Up to this time, we have been using FireWire and it still proves to be the best technical solution.

The second problem is a little more complicated. Sound degradation caused by the operating system was true with Windows XP and standard WDM drivers. XP's audio engine relied on a mixer (KMixer) that would resample all audio to 48 KHz so everything output from the PC would use the same sample rate. There are some ways to avoid resampling, but if you adjusted the volume or simultaneously allowed sound output from other applications (including system sounds), resampling was performed. That means the CD's 44.1 KHz sample rate was always converted to 48 KHz. Another problem with this audio engine was that to lower the sound volume, the data was simply truncated to a lower resolution. So 16 bit audio was reduced to 14, 12 or 10, etc., bit data to get a lower volume. This can dramatically decrease the sound quality.

This is where the thread then moves on to the bit-perfect discussion. To avoid degrading the sound by modifying or truncating the bits, you could use a driver like ASIO that bypasses the Windows audio engine so that the original source audio data is not changed all the way to the DACs. This is how you could get bit-perfect output. Of course the software players had to provide support for these sort of drivers. Windows Media Player or Windows Media Center do not. So you had to use other players like J.River's Media Center, Winamp (with a special ASIO plug-in), Foobar, etc., to achieve bit-perfect performance. Now with Vista, a couple things have changed. First, the audio engine is much better. Even if the audio is resampled, the algorithms are much better and the effect on sound quality is not nearly as bad as what happened in XP. They've also improved the volume control so that they no longer truncate the bits to reduce sound levels. Instead, it converts the data to 32-bit floating point, then performs the volume adjustment calculations and then converts back to the original sample rate. This basically gives you lossless attenuation. It's not bit-perfect, but there is no degradation in sound quality. Some dedicated audio hardware that uses high quality DSP chips use this same technique. For the purist, who still want bit-perfect operation, they can still use ASIO drivers if they've been updated to work under Vista. These drivers will also bypass the audio engine, just like they did with XP. Vista also supports a new feature called "exclusive mode". Exclusive mode also bypasses the Vista audio engine and will provide bit-perfect playback. However, you need an application that supports exclusive mode and most I'm familiar with, like J.River Media Center, Windows Media Play, Vista Media Center, Foobar, etc., don't.

Getting back to the diyAudio thread, the bit-perfect discussion mentions that there is a newer software player, called XXHighEnd, that uses Vista's exclusive mode. There's another program called XMPlay that can run in exclusive mode when using a WASAPI output plugin. The sound output from a program using an ASIO driver or running in exclusive mode should be identical, because bit-perfect is bit-perfect. However, several people, including the original poster and the developer of XXHighEnd (not the same person), claim that XXHighEnd sounds better than other bit-perfect solutions. In fact the original poster was also a big fan of using Foobar with ASIO drivers, and he claims the sound has improved a lot when using XXHighEnd. When asked how something that outputs the exact same data can sound better, the developer doesn't provide any answers that satisfy the skeptics. The closest he comes to any technical explanation is that he does something to minimize jitter. But that doesn't make much sense given the way the audio chain works. If the audio data is buffered and the DAC is driven by a local clock, the audio software player shouldn't have any effect on jitter. He also admits that he doesn't know why it sounds better, but that there are many ways a software application can have an effect on the audio quality and he's just been tinkering around trying to find the best sound quality. That's where things get confusing to me. Or as another poster/skeptic put it:
  1. It's bit-perfect
  2. PCM needs to be processed some special new way to sound best
  3. No, it's bit-perfect
  4. If you were to, say, play a byte later in the stream than it was originally, that might be useful
  5. No, really, it's bit perfect!
  6. You're mucking around with the data based on some theories you have that you won't explain and if we don't just accept that it is bit perfect and magically sounds better than we are just mean, old unbelievers.
  7. Oh, and it is bit perfect.
The developer of a kernel streaming (KS) output driver, which is also achieving bit-perfect performance like ASIO drivers, compared the output from three different bit-perfect solutions - Foobar2000 with his KS output driver, XMPlay running in exclusive mode and XXHighEnd running in exclusive mode using it's third engine. Using an oscilloscope, he found that the output was identical. They are all bit-perfect. He also says he cannot hear any difference, so he doesn't recommend the XXHighEnd software because they charge for it (and Foobar2000) is free, the user interface is pretty weak and the program is immature. Like I said, others, including the original poster, claim it sounds better.

I have to admit, if it sounds good to you, I'm not going to try to convince you otherwise. I'm also not convinced bit-perfect output is the only acceptable way to listen to audio. Especially since Vista is not bit-perfect, unless you use exclusive mode, but it still sounds great because any changes are lossless.

Friday, April 04, 2008

Free! The Art of Persuasion Compilation from Magnatune.

Last August, I received an email from Magnatune telling me about their free compilation album called "Seduction Music." They also said they were going to offer a new free compilation every month. So everytime they sent me another email, I was planning to pass this information on to my readers. Well I never did get another email announcement, so that was the last time I posted anything regarding Magnatune's free monthly compilations.

Well I guess just because I didn't get any more emails doesn't mean they stop providing free compilations. In fact, I followed my old link from the original article and discovered a new compilation titled, "The Art of Persuasion." I apologize for missing the last 6 or 7 months. Hopefully they will repost some of those in the future.

Thursday, April 03, 2008

Vista Audio Playback, Part 1

I've been following this thread on diyAudio Forums titled, "Is Vista really capable of bit-perfect output"? There are some comments that I thought readers of my blog might find interesting. As you can see I added Part 1 to the title of this thread. I don't know if this is really going to be a multi-part article, but what the heck, I'll add it to the title just in case.

The original poster starts out by telling us what audio equipment he's using. He has a PC running Vista Ultimate. For the PC's audio, he has a MOTU 896HD sound card, which is an 8 channel 24/192 audio interface that costs around $1,000. This is connected to his PC via a FireWire connection. He uses the digital AES/EBU outputs of the MOTU to connect to the digital inputs of his Esoteric D70 external DAC. Esoteric, which is a division of Teac, doesn't look like they still sell the D70, so I couldn't find a link to their product information. Anyhow, it is/was a pretty highly regarded $6,500 stereo DAC. It's a shame that he's only using 2 channels from his multichannel MOTU interface. Next, the analog output from each channel of his D70 are sent to Pass Labs XVR1 active electronic crossovers. Each of these babies normally cost $5,000. Each crossover is taking a input signal and dividing them into high-pass and low-pass outputs. For a stereo system, you normally have the left and right channels feeding a single XVR1 and it outputs the low frequency and high frequency signals for each channel. So that is two channels in and four channels out. In this case, since he has 2 XVR1s, I assume he is splitting it up so that the left and right channels are each getting 4 output channels. These 8 outputs are connected to 8 Hypex UcD700 amp modules. So that's 4 amp modules per channel. I have no idea how much he paid for his amps, but that's a lot of power. Each one of these UcD700s provide 700W rms power. That's 2,800 Watts per channel. Most likely, this was a diy project. It might not be as expensive as a commercial product with similar performance specs, but based on the other components in his system, I doubt he scrimpted on the parts for his amps. Just to give you an idea of the price of a couple components he probably included, the amp module and matching power supply for the UcD700 cost up to $500 and $350 respective (using the current exchange rates). Since he probably has 8 of each, just those components cost $6,800. Next add in the transformers, interconnects, chassis, etc. and his amp probably cost at least $7,500 - $10,000. The amps are feeding a pair of Wilson Benesch Chimera loudspeakers that cost somewhere between $21,000/pair and $33,000/pair, depending on your source of information. So, if price is a determining factor, this approximately $50,000 sound system must sound pretty damn good.

Now why would someone connect a PC to a high-end system like this instead of an expensive high-end audiophile CD, DVD-Audio, or SACD transport? Actually he does own one of the $7,500 Esoteric P70 transports, but still prefers the sound through the PC. When asked if the PC chain was really better or just different, he responded that it was definitely better. Then he gave an example of a test he performed to compare the sound of a CD playing from his P70 transport to the sound of the same CD ripped as a WAV file to his hard drive and the same song downloaded from Linn Records website in a 24/96 FLAC file. He said, "
When played through Foobar, the FLAC version is simply stunning. The Wav version is very good, though flatter than the FLAC. The CD played through the transport sounds more edgy, less fluid and less solid." Then someone responded that there must be something wrong with his transport because he has a modded version of the same one and it sounds perfect. To which, our original poster responded:

"I agree, the standard P70 is a stunning transport. I've not heard any modded versions, so can't comment on their performance."

"I don't think there's anything wrong with my transport though. It's dead silent when playing CDs and handles (my wife's!) badly scratched CDs easily. It literally blows my Pioneer DVD, acting as a transport, out of the water. No, I'm pretty sure it's doing a sterling job, given the constaints of the ancient 'red book' standard."

"But as you yourself admit, the standard P70 is not perfect. You reckon that the modded version sounds "even more relaxed, richer and bigger". Well, I reckon you get all of this (and maybe more?) by extracting and playing wav/flac files well."

"As for 24/96 FLAC files, I'd venture that no transport on the planet, modded or not, comes anywhere close to the sound quality you can get from them. If more and more companies start offering these downloads, I think the audiophile community is simply going to have to start taking more of an interest in PC music."

I guess I will make this into a multi-part article, since I'm going to go ahead and post this now and then continue with the discussion about Vista playback in the following parts.

Thursday, March 27, 2008

Reference Recordings - New HRx High Resolution DVD Audio

Just recently I came across some news that the independent record label, Reference Recordings, is planning to sell their music in high resolution audio formats. This isn't some revolutionary new audio format, even though some blogs seem to be presenting it as such. Nevertheless, I think this is good news for people that want to listen to high resolution audio. Basically, they are planning to copy their music to DVD-R discs and sell them to people who will load them in their DVD drives and copy them onto their computer or media servers for playback with their computer. Obviously, you don't have to copy them off of the DVD-R disc to play the music, but most probably will copy them to their music library because of the convenience. It seems like the people at Reference Recordings are another group who understand the advantages of using a PC for playing music.

They are calling these recordings HRx recordings. Hopefully this won't confuse people into thinking there is a new format war that will require some new specialized player like DVD-Audio or SACD. Don't worry, it's not. They are just copying the digital masters, which are 24bit/176.4KHz .WAV files to DVD recordable discs. These DVDs can be read by any PC's DVD drive. You won't be able to play these files using your CD or DVD stand-alone players. Reference Recordings’ legendary audio designer and engineer “Prof.” Keith O. Johnson, who co-developed the HDCD process and has received seven Grammy nominations for Best Engineered Album, stated that the files allow people to hear for the first time all the information on their universally praised master recordings.

I'm not sure when they are going to start selling these discs. There's no information on their website about this. I've also read that this is just an interim solution until they can offer these files as downloads from their online store. Hopefully, they will use lossless encoding to help reduce file sizes and speed up downloads.

Monday, March 24, 2008

New HTPC amp

There's recently been some discussions on AVSForum about a new amplifier board that was developed by D2Audio. Actually, most of the comments have been about a new MSI 7411 motherboard that supports the D2Audio technology. Instead of using the typical on-board 7.1 HD-Audio chips like those from Realtek, they have included D2Audio's DAE-3 class-D PWM controller with this motherboard. This controller includes the standard HD-Audio interface and works with one of two add-on PCIe cards, either a 7.1 preamplifier card or a 5.1 amplifier card.

This isn't the first time someone has integrated an audio amplifier with a PC motherboard. A little over 5 years ago, Acer introduced their AOpen AX4B-533 Tube motherboard with built-in tube amps. I don't know how well it sold, but it got some attention, probably because of the novelty of the combination. Obviously, it didn't revolutionize the way other manufacturers designed motherboards because we haven't seen anyone else release a similar product until now. However, it does look like more PC manufacturers are working toward making convergent products and taking the HTPC market more seriously. This time, instead of using tubes, the D2Audio amps use class-D circuitry.

These products are exciting to AVSForum readers because they may finally have an HTPC that can replace their A/V receiver and many of the source devices. With something like this, you wouldn't have to deal with the current hassle of trying to pass HD encoded audio, like Dolby TrueHD and DTS-HD MA, via HDMI to your AVR. You can just connect your HTPC directly to your hifi speakers. I guess the next question is, how will it sound compared to a good AVR? Based on D2Audio's literature it is designed to compete head-to-head with current AVR gear. Chris Morley, President of Omaura North America has listen to it and says it sounds fantastic.

I don't doubt that it would sound as good as a low to moderate priced AVR, but after researching class-D amps for several years, I'm skeptical that this technology can sound as good as dedicated or even integrated amps. For those of you that are interested in high end sound quality, I created this chart to compare common specs of the D2Audio amp card to other class-D amp modules:

ProductPower Rating
Distortion
THD+N
SNR / Dynamic Range
Power Efficiency
Peak Output Current
Frequency Response
D2Audio 5-Channel x 100W (AAIC100-5) Card
100 W
Peak
at 8Ω
less than 0.1%,
f = 1KHz, P = 1W
more than 105 dB
93%
?
±0.5 dB (20Hz to 20KHz)
ICEpower250A
125 W
at 8Ω,
210 W at 4Ω
0.005%,
f = 1KHz,
P = 1W
112 dB
A-weighted
93 %
> 25 A
±0.3 dB (20Hz to 20KHz, all loads)
Hypex UcD180
HG Version
105 W
at 8Ω,
180 W at 4Ω
0.008%,
f = 20Hz to 20KHz,
P = 1W
120 dB
A-weighted
92 %
10 A
±0.3 dB (10Hz to 50KHz, all loads)
Huygens
MHzpower-2
100 W at 8Ω,
200 W
at 4Ω
0.0035%,
f = 1KHz,
P = 10W
123 dB
91 %
26 A
+0/-3 dB
(DC to 150KHz, at 8Ω)
CAD Audio
D250A
250 W
at 4Ω
0.02%
typical
110 dB
?
20 A
+0/-1 dB
(20Hz to 20KHz)
CL3 Gemincore
250 W
at 8Ω
0.002%,
f = 1KHz,
P = 1W
115 dB
97 %
19 A
0 to 70KHz
PowerPhysics A-108
100 W at 8Ω
less than 0.05%
P = 0.1W
115 dB
A-weighted
more than 90 %
?
20Hz to 20KHz

It's hard to make valid comparisons because all manufacturers don't use the same measures. My first concern with the D2Audio amp board is its power rating. To be fair, I limited the comparison to modules that were close to the AAIC100-5's power rating of 100W. D2Audio has calculated the power rating based on an 8Ω speaker load. A lot of the amp manufactures will quote power ratings based on 4Ω loads, but 200W at 4Ω is similar to 100W at 8Ω. The specs from D2Audio's website list their power rating as 100W peak at 8Ω. Most of the other manufactures will list the power rating using an rms (root-mean-squared) calculation. D2Audio may mean you can get 5 x 100W peak power for a short period of time before the PC's power supply cuts out. That's probably why they state in their literature, "the DAE-3 engine provides real-time power management to protect against power supply overload and potential Media PC shutdown from loud music or explosive sounds that occur during movies or games." So maybe if you have a large enough power supply it can provide a continuous 100W rms power. If not, if they really mean peak, then the rms power is actually 50W per channel.

The distortion figures for the AAIC100-5 are not that impressive when compared to most of the others in the chart. Not too bad when you compare it to some tube amps, but not as good as most solid state AVRs on the market. It also depends on the type of distortion. A tube amp may have a lot more distortion, but some people perceive the relatively high 2nd order harmonic distortion to be pleasing and adding "warmth" to the sound. Even though solid state amps have much lower 2nd order harmonic distortion, the other higher order harmonic distortion is not too pleasing. With most inexpensive solid state amps, the distortion increases as frequency increases making them sound bright or harsh. The THD (total harmonic distortion) for class-D amps are primarily second harmonic in nature, but there are also some higher order harmonics present. The best class-D designs use a feedback loop to compare the output to the input so they can minimize any errors in the output. With a pure digital PCM-PWM amp, you have nothing in the input to compare to, so without some pretty expensive and complicated circuitry, it is nearly impossible to get good distortion ratings. That's probably why D2Audio's digital amps don't match the THD specs of these other analog class-D designs. It's also probably why most respected class-D designers abandoned the pursuit of pure digital amps a few years ago in favor of analog class-D. I've been very impressed with Hypex's UcD amp modules and if you look at their THD figures you can see why. They are able to get very low THD over the entire frequency range (well at least from 20Hz to 20KHz). Older class-D amps without feedback circuitry had pretty poor THD at higher freqencies and this is why they were used mostly in active subwoofers and got a bad reputation for true hi-fi. I hope the high frequency performance of the D2Audio PCIe amps don't help to reinforce that reputation.

You can also see that the dynamic range of the AAIC100-5 doesn't compete with the others in the table. Considering the fact that many of the DACs in popular soundcards have SNR specs around 120 dB, the D2Audio amps might become the weakest link in the audio electronics chain of your system.

The other specs compare favorably to the others in the chart. Power efficiency and frequency response are in the same range with the other amp modules.

There are a few other audio specs that are not listed in D2Audio's literature that would be worth knowing. Since the AAIC100-5 is installed inside your HTPC and is dependent on the PC's power supply, I'd like to know the spec for power supply rejection ratio (PSRR). PSRR indicates how good a device is at rejecting noise from the power supply. The PSRR of the ICEpower and Hypex amps are about 60 and 65 dB, respectfully.

In conclusion, I think the new MSI motherboards with integrated D2Audio technology is a pretty cool thing. I'm happy to see any product that makes HTPCs more useful and popular. I'm not a big fan of digital amps, mainly because their specs, especially THD, don't measure up to good quality class-D analog amps. I also don't like the fact that these amps are totally dependent on the PC's power supply. If you've read some of my previous blog posts about HTPCs, you also know that I like my HTPCs to be pretty small. Ideally, I'd like a fully functional HTPC about the size of a Mac Mini. This would be impossible if you throw in the amps. So, unless this sort of technology makes some dramatic improvements in the future, you won't see anything like this available from Amplio.

update 3/28/08: I received a more detailed datasheet for Huygen's MHzpower-2 amp module and noticed some differences with the specs in my chart. So I updated the chart above to match their datasheet. I also noticed that the PSRR of the MHzpower-2 is 71 dB. These are pretty impressive specs. Unfortunately, I haven't had a chance to test them out. Fumac, if you read this post, please remember to email me your price sheet. I also haven't read or heard any feedback from any of Huygen's customers, but I know there are a few European amplifier manufactures that are using the Huygen modules in their expensive amps.

Thursday, February 28, 2008

More Hypex Announcements

Hypex, the Dutch electronics company known for their high quality class D amplifier technology, sent out a newsletter yesterday announcing a couple new products.

First, they announced a new line of switch mode power supplies designed for use with audio amplifiers, especially Hypex's own OEM series of class D amplifier modules. The first one, the SMPS180, will be available some time this summer ('08).

The second announcement was for their new 2500W (yes, this was not a typo, it is 2500W not 250W) class D module, called the UCD2kW. It will also be available coming up this summer ('08).

Tuesday, February 19, 2008

Web Anonymity Bites Back

One of the class D amp / SMPS module manufacturers I've been watching is the Spanish company, Coldamp. The owner/designer's name is Sergio Sanchez Moreno. Coldamp is one of the few companies that offer both an audio grade switching power supply (SMPS) and class D amplifier modules. The advantage to the SMPS, especially with a multichannel product, is the decreased weight and size. The challenge is to get them to sound as good as a linear supply. Sergio claimed Coldamp's SMPS sounded better than linear supplies and several DIY'ers from the diyAudio forum supported this claim. They also claimed the Coldamp class D amps were comparable to Hypex's highly regarded UCD amps. I don't think anyone was suggesting that they were better. Just different, but in a positive way. Several DIY'ers were satisfied with using a combination of the Hypex UCD amps with Coldamp's SMPS.

Anyhow, we are following the progress that all designers are making with both class D amps and SMPS development. Probably the most respected designer, Hypex's Bruno Putzey, was just written up in IEEE Spectrum magazine. You can read the online version of the article here.

I have also noticed that our blog regularly gets several hits from people doing a Google search for Coldamp. So obviously there is some interest in their products that seem to direct traffic to our blog. Since we have a few posts announcing Coldamp's products (see: Coldamp Plans to Offer 750W Class-D Amp Module), I felt obligated to update our readers with some disappointing news. The moderators of diyAudio have confirmed that Sergio was also signing on with another alias, named Pierre, claiming to be a happy Coldamp customer. It appears Sergio was using this alias on other websites as well. Most of the time, he was posting as just a very satisfied Coldamp user, sharing his experience with others looking for advice. As misleading as this may be, sometimes Pierre's posts were basic design and engineering questions directed to the experienced engineer's on the forum. These experienced engineers are particularly upset with this deception since they may have helped a potential competitor. They are also shocked that many of Pierre's questions were so basic that it demonstrated a fairly elementary level of expertise with the technology. One experienced designer/engineer named JohnW, stated, "Reading back though the "Questions" posted as Pierre; some are at such a basic fundamental level that they should never have been asked by a competent designer already SELLING SMPS!" Another diyAudio forum member, Eva responds, "The main problem is not how a designer gathers the knowledge, it's the fact that it's completely unfair to advertise and sell your very first prototypes as if they were state-of-the-art class D and SMPS, when they are full of hidden pitfalls that you don't know how to solve or don't know about at all because you still have a lot to learn."

Since this discovery, Sergio and his alias, Pierre have been banned from diyAudio's forums. I've also noticed that Coldamp's website is now down. So it appears they might be out of business. I think this is extremely unfortunate. Hopefully, Sergio and Coldamp can come straight and avoid a total collapse. Some of Coldamp's customers have posted in the diyAudio thread that they are happy with their purchases and felt the service and support from Coldamp has been very good. They work and apparently many people say they sound great. The problem is with how they learned to build class D and SMPS products, and are they really going to be safe and reliable over the long term?

Here's the diyAudio thread, in case you want to read more comments and judge for yourselves.

Thursday, January 17, 2008

30 Minute Music Hour

My friend Andy Moore has a very cool new show on the Wisconsin Channel (WPT 21.2) called "The 30-Minute Music Hour." I don't know quite the best way to describe the show. It's kind of like Austin City Limits without the studio audience. It's a bit more intimate because Andy talks a little bit with his guests between songs.

For those of you in the Wisconsin viewing area, be sure to check this out. Here's the current schedule:

#101 30-Minute Music Hour – Pat MacDonald

Digital (20.2, aka The Wisconsin Channel),

January 18, 10:30 am and 5:30 pm.

January 19, 6:30 pm.

January 20, 6:30 pm.

Analog (WHA, etc.)

February 9, 10:30 pm (lead-in to Austin City Limits)


#102
30-Minute Music Hour – Robbie Fulks

Digital (20.2, aka The Wisconsin Channel),

January 25, 10:30 am and 5:30 pm.

January 26, 6:30 pm.

January 27, 6:30 pm.

Analog (WHA, etc.)

February 23, 10:30 pm (lead-in to Austin City Limits)


#103 30-Minute Music Hour – Willy Porter

Digital (20.2, aka The Wisconsin Channel),

February 1, 10:30 am and 5:30 pm.

February 2, 6:30 pm.

February 3, 6:30 pm.

Analog (WHA, etc.)

February 27, 10:30 pm (following American Masters: Pete Seeger)


For everyone else, you can watch it streaming from their website. Here's a writeup on Andy's program in Isthmus' 'The Daily Page'.

Sunday, January 13, 2008

CES - Day 3

I spent a little more time viewing HTPC solutions during my third and final day. I started at the Central Hall of the Las Vegas Convention Center where there are a few really large booths for the big electronics and computer companies. Sony was there showing their Blu-ray technology and acting a bit smug about Warner's recent announcement that they will exclusively support Blu-ray from now on. The Sony guys were careful not to say anything about what this means for them, but it was pretty obvious that they think the format war is coming to an end and they will be declared the winner. They mentioned that the HD-DVD camp was scrambling to figure out what to do next. Like I said in a previous post, since an HTPC owner can purchase a dual format (Blu-ray & HD DVD) drive, it doesn't really matter what format a movie is on. However, I'm a little concerned because it sounds like people have more problems trying to play Blu-ray discs and less with HD DVD with their dual format LG drives. Microsoft doesn't seem too happy about these recent events, but they are also saying this doesn't really effect them that much. Microsoft certainly would have benefited if HD DVD came out as the winner, because they developed and license the interactive layer (HDi) for HD DVD. A Microsoft guy said they will still move forward with HDi and offer it with downloadable content. A lot of people, including Microsoft seem to be saying that the real winner in a few years will be downloadable and streaming content and that optical disc media will be unnecessary. I've got mixed feeling about this because HTPCs are the perfect device to use with downloadable content and our business currently depends in large part on the success of HTPCs, but the bandwidth is pretty limited (at least in the U.S.) and it currently isn't real practical to download content with quality comparable to HD DVD or Blu-ray (1080p video and lossless multichannel 24bit/96KHz audio). If they downrez and lossy compress the video and audio to 720p and 16bit/48KHz quality and people are content with this, just like they've accepted compressed audio formats like MP3 and iTune's AAC, then we've taken another step back in quality. Hopefully, since people seem to be very excited with the latest 1080p display technology, they will demand content that takes full advantage of its resolution. Once they experience high quality video from their new 1080p displays, they might just invest in an audio system with quality to match, like the products were are developing.

Speaking of new display devices, I stopped by the booths of Sharp and Samsung. While standing and gawking at the big Sharp LCD displays, I had a conversation with a technology guru from Disney. He recommeded that I should take a look at Samsung's OLED displays because he is confident that within 5 years it will be the dominant display technology. He thinks it will be cheaper to manufacture, provide higher quality and be the most green technology, which is very important for all products from now on. He might be right, but I was still pretty impressed with the panels Sharp was demonstrating in their booth. The LCD technology has evolved over the past year. Last year the big deal was 1080p. Now everyone does 1080p. Another big thing last year was panel size and that hasn't changed much over the last This year it seems to be 120 Hz or higher refresh rates. The other thing is style. Many of the manufactures are showing off their ultrathin panels and the high quality finish of the frames. Sharp was showing off their 108" (or was it 120") monster. The photo on the right is one of their ultrathin 120 Hz displays (sorry about the quality of the pic, I prefer to turn off the flash, but since it's relatively dark in the exhibit hall, I have to keep the aperture open for up to 1/4 sec. and sometime they come out blurry).

Samsung had a huge booth at CES this year. They seem to be into everything. A guy at their camcorder area said they (Samsung) wanted to reach the same level of success in camcorders as they have with LCD televisions. Speaking of camcorders, Canon was demonstrating their compact HD camcorders they plan to release this Spring. Wow! Being the owner of a 3 CCD DV camcorder, I never would have expected such great colors from a single sensor camcorder when compared to my Sony TRV900 DV camcorder. On top of that, you get great HD resolution, a very convenient, portable size and instead of using tape, you can use SD flash memory. I'd tell you the name and model, but I seem to have lost the brochure. Oh well, back to Samsung and their display screens. Samsung was also showing off their big 120 Hz displays. And of course they had the stylish ultrathin technology as well. They even had a big ultra high resolution (3840 x 2160) screen which they claim is 4 times the resolution of conventional LCD. I don't quite follow their math if they are comparing it to 1080p because it comes out to twice the resolution (maybe since it is 2 dimensions, we are getting 4x the number of pixels). Either way, it is pretty impressive looking. Finally, I made my way over to the OLED displays. Samsung was demonstrating their 31" OLED. After looking at this, I hope the Disney guy is right and we get to buy inexpensive 60" OLED displays in the near future. These things are beautiful. The colors seem to be really great without looking over saturated like some LCDs. And the contrast ratio, 1 million to one, that's as good as your eyes can see. These really are great looking. Oh, and they're thin as well.

I also wanted to check out the Nextgen Home Experience, but the lines were too long and I had places to go and people to meet.

Then I went over to the South Hall of the Las Vegas Convention Center to talk to a few more companies. BridgeCo is a manufacturer of FireWire and USB interfaces for audio and video. The guys manning their booth (or meeting room) weren't very helpful. I explained what I was doing and they responded that they didn't support multichannel surround playback with either technology. They said their solutions are really geared to pro-audio and this isn't going to change in the future. ArcSoft also had a meeting space in the South Hall. They are the developers of another Blu-ray/HD DVD software player that many people on AVS Forum have been raving about. They currently have a trial version of their Japanese version and are planning to release the English version in the very near future. It may have already been released. They gave me their Product Licensing Guide with a DVD full of evaluation versions of all of ArcSofts applications, including TotalMedia Theatre, which is the player everyone is excited about. They also gave me the business card of the VP of Sales and Marketing and told me to contact him to get a full version sent to us.

While walking around the South Hall, there were a couple of TechZones I wanted to check out that sounded interesting. One was the Sustainable Technologies area that was said to "explore the pioneering technologies that benefit the environment, sustain the global economy and improve daily life in developing countries." I wanted to see if they had more ideas of how we could improve in this area in addition to what we already have with highly efficient Class-D technology. Unfortunately, they weren't located where they were shown on the program map. There were a bunch of lounge chairs, which are shown on the map, but nobody was there except a few people grabbing a bite to eat. Nearby there was the Advanced Display Technology TechZone. I didn't find it very interesting because it was mostly displays for mobile devices.

Walking between sections of the Las Vegas Convention Center, I ran into a jazz performance sponsored by MusicGiants. These are the folks that offer high resolution downloads from their online music store. Their booth was suppose to be at the Sands Convention Center, but as it turns out they were really located here. I was planning to stop by and talk to them, so I was glad I didn't search for them at the Sands. I told them about my business and how potential users of my product would probably appreciate their higher resolution audio. The guy I spoke with recommended I contact Elliot Mazer, who is a pretty well known audio producer/engineer who is trying to encourage high-end audio manufacturers to develop technology that will be compatible with their downloads.

Next, I headed over to the Sands Convention Center to visit the booths of MusicIP and SiliconDust. MusicIP has a software application that can generate playlists from your music library by analyzing a song and finding others that are a close match. They just came out with a plug-in for iTunes and are working on one for Windows Media Player. It's pretty cool technology, but not as flexible as what I can already do with J.River's Media Center. SiliconDust are the folks who provide the HDHomeRun. They said they are working on adding functionality to support satellite dish and encrypted cable (cablecard) in future products.

For the remainder of this day, I spent time back at the Venetian to listen to more high performance audio. I'm not particularly impressed by a lot of the expensive stuff on display in many of the suites. Many of them just seem to be ultra expensive monstrosities. This is where I think the "emperor has no clothes" tale is really true. I don't like to bash other products, but I pretty much share the viewpoint of Gene DellaSala who wrote this report for Audioholics. I too was impressed with Dali's on-wall speakers. I didn't think you could get such great sound out of these type of speakers.

Okay, that's about all I have to report on CES 2008. The fourth day was basically a travel day, so nothing to talk about there. All in all it was a pretty good show. I had the opportunity to talk with several potential partners that specialize in industrial design or manufacturing. I got several recommendations for high quality manufacturers in Asia, which is very important at this stage.

Friday, January 11, 2008

CES 2008 - Day 2

On Tuesday I walked up to the Sahara Hotel to buy a monorail pass and travel to the Las Vegas Convention Center. I visited the Microsoft booth and talked to some of the people involved with Media Center and some others with Windows Home Server. I'd really like it if Windows Home Server were part of my TechNet subscription, so I tried to find someone that could forward my request. I also wanted to find out why there isn't better integration between Vista Media Center and Windows Home Server. It sounds like better integration between the two is definitely in the plans. Microsoft's eHome Program Manager told me that adoption on Vista Media Center has been very good and based on EPG (electronic program guides) downloads, the data supports this assertion. I gave him my card and he is going to send me this data if he can.

I also visited the DTS booth. They were demonstrating their Surround Sensation technology that creates a virtual surround from only 2 channels. I listened to the headphone demonstration, which played the same clips from the original 2 channel mix and the enhanced virtual surround version. I think it did a pretty good job, at least it seemed better than the surround headphone technology that Lake Technology licensed to Dolby a few years ago. I still wasn't very impressed with DTS's demonstration because the levels were so much different between the stereo and surround samples. It's pretty hard to determine which is better when the volume level is so different. Of course the Surround Sensation sample was much louder than the stereo sample, so it seemed to be much better.

After talking to DTS's Director of Product Management about licensing, I walked toward the next exhibitor on my list, Dolby Labs. My left show felt very loose, so I look down to see if my laces untied. I noticed the laces were still tied, so I lifted my foot to get a better look. The sole of the shoe was separating from the upper part. It was falling apart with every step. I realized that I couldn't continue walking around with my shoe coming apart, so I headed to the exit to get a cab to drive me back to my hotel so I could get the only other pair of shoes I had with me, my Nike running shoes. I must have looked like thump-drag because I had to drag my foot on the ground so the shoe would hold together. That didn't really help. The shoe came completely apart just before I reached the elevator to go up to my room. The pic on the right is what they looked like just before I threw them in the trash. Anyhow, that wasted a good chunk of my day.

From there I went to the Venetian to check out the "high performance audio". More and more of these vendors are realizing that computers are pretty good at storing and playing music. Many of them had their equipment connected to PCs. Some of them were just using a S/PDIF connection to their high end processors or preamps. Others had USB connections. Most were limited to 2 channel stereo sound. The only ones playing surround were playing off of stand alone players. If you want to see some pretty pictures of some of the equipment at the high performance audio exhibits, check out Steve Guttenberg's blog.

For those of you that are frustrated with audio playback of HD DVD or Blu-ray discs using Cyberlink's PowerDVD, I wish I had some good news. I stopped by Cyberlinks suite at the Hilton to see if I could speak with them to learn what we need to do with our products to support high resolution playback (with no downsampling, etc.) and the whole protected path. Since I didn't schedule an appointment, they wouldn't speak with me. I tried setting up a later appointment, but they weren't interested. I was also interested in speaking with representatives from TC Electronics. They sell the DICE chips, which are suppose to be pretty good IEEE1394 (FireWire) chips. When I went to the TC Electronics booth I learned that it was a different company. There was another booth for a company called Dice Electronics (you never know, maybe they are changing their name to match their flagship product). Both of these companies were selling something related to automobile electronics.

I did spend some time speaking with representative for HDMI, USB and IEEE1394 technologies. The USB folks had a section of the exhibit floor with several companies displaying their solutions. None of them were dealing with USB audio. I did get a chance to meet with the Chapter leader for the USB3 spec. He mentioned that they've received several requests for allowing clocking from the host system over USB3. That's currently a big problem with USB1.1 and USB2 because you have to reclock everything if you use USB. Anyhow, he said they are considering adding this to the USB3 spec. I also met with the people that are promoting IEEE1394 at the HANA Alliance. Obviously, they think we should stick with FireWire and they made a pretty good case. They also seemed to endorse the DICE technology as our best solution.

CES 2008 - Day 1

My flight arrived in Las Vegas at around 2:30 PM. Then it took at least 30 minutes to get my luggage. I also had to wait another 45 minutes for the shuttle bus to show up. By the time I got to my hotel room at the luxurious Circus Circus Hotel and Resort, it was about 5:30 PM. There wasn't enough time left in the day to visit any exhibits, so I just stayed in the hotel. Las Vegas traffic really sucks, especially when they have a big event like CES. So after I got unpacked, I called home to let my wife and kids know I arrived safely. Then I went downstairs to eat dinner and watch "The Ohio State" Buckeyes lose to LSU in the National Championship football game. Oh well, another let down for the Big Ten. How can Ohio State lose 2 years in a row?

CES 2008 Overview

I attended the Consumer Electronics Show in Vegas again this year. As usual it was big, crowded and flashy. The main reason I went to the show was to network with people that might be able to help us with our development. Since CES isn't really a developers conference, there was limited opportunities to meet with some of the people or companies that can really help us. Many of these companies only send their sales and business development people, so you usually don't get to speak with the engineers. However, sometimes the business development people can be fairly helpful. Some of the chip manufacturers were there, but many of them don't have exhibition booths and instead only meet with people by appointment in their meeting suites. Unfortunately, some of them don't really want to take the time to talk with small companies like ours. I also enjoy seeing the latest and greatest electronics, so I try to save some time for browsing the big companies booths. There weren't any significant announcements, so it didn't seem to be all that exciting.

I decided to attend CES Monday through Thursday. This actually worked out to only two productive days, because I arrived late Monday afternoon and had to leave early on Thursday. Prior to leaving Madison, on Sunday night I watched Bill Gate's opening Keynote address streaming live over the Internet. This was suppose to be his last keynote since he is stepping down from his full time position with Microsoft to work full time on the Bill & Melinda Gates Foundation. I thought he might include some big announcement, but there really wasn't a lot to really get me excited. They showed a pretty funny video clip of Bill contacting a handful of celebrities and asking them for help or advice on what he can do after retirement. BTW, the image quality of his address was much better than this link's archived video. You'd think Microsoft would want to promote the highest quality video to help promote online streaming or even provide a high quality video for download.

I think it was a good thing that I didn't fly in earlier just to see his last keynote live. I was able to save a little money. Besides, it's nearly impossible to get a seat in the hall. I think it must help to have some good connections to get tickets to these sorts of things. Since it was his last keynote it might have been cool to be there...