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.
Monday, June 16, 2008
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.
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:
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.
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:
- It's bit-perfect
- PCM needs to be processed some special new way to sound best
- No, it's bit-perfect
- If you were to, say, play a byte later in the stream than it was originally, that might be useful
- No, really, it's bit perfect!
- 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.
- Oh, and it is bit perfect.
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.
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.
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.
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:
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.
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:
| Product | Power 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.
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.
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