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About Ajax

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  1. Hi Everyone, Firstly, thanks to all the contributors to date. Many differing views but in the main expressed in a cordial and informative manner, so thanks for that. I received an email from Mark Waldrep wherein he advised he had trouble exceeding his dropbox limit, which is why many of you could not download the files. He is now using google drive. Trouble viewing this email? Read it online The HD-Audio Challenge II has launched. Over 250 audio enthusiasts have already signed up and more are signing up everyday. Please feel free to encourage others to participate in this new research project by linking to this page. Anyone interested should submit their information using the form on the following page: CLICK HERE FOR THE FORM TO SIGN UP Last week, Dropbox informed me that they have banned my account because I exceeded my daily download allotment. So I moved all of the files to a Google Drive and have been sending the link to everyone that has signed up. If you haven't received the link, please be patient. I'm adding about 25-30 people every day to avoid swamping the Google account. Once you have the files, please let me know.
  2. Sorry for the off topic but could you pls expand on your statement "Then I installed proper electrical isolation between the computer and the USB input circuitry and the DAC." Should that have been "of the DAC? Irrespective of the semantics what exactly did you do to electrically isolate the DAC from the computer and enjoy such a large increase in sound quality. I assume the overall purpose / result was to mitigate noise?
  3. Hi Audiobomber, Here is the reference I believe that you are referring to, which is from Mark Wadrep's Dr AIX site. He is obviously a fan of Benchmark Media's DACs and AMPs's, as am I. Mark starts of by saying: I'm really fortunate to have friends that are smarter than me. In many aspects of life, it's great to be able to discuss and learn from people with different areas of expertise and life experiences. So when I authored a recent blog on "highly resolving" systems and whether they are necessary (you can read that article by clicking here ), it was a welcome surprise to hear from one of the smartest people I know, John Siau, the principal designer of both analog and digital systems at Benchmark Media. I consider their DACs to be among the finest on the planet — equally at home in my mastering room all these years AND in my home system. Benchmark supplied their DACs and power amplifiers for all of the 5.1 HD-Audio demos that AIX Records assembled at AXPONA shows. Benchmarks' hardware and my recordings delivered a music experience unlike any demo at any trade show in the history of trade shows. Why do I feel confident in making that boast? Because the entire signal path from source recording to speaker output was truly capable of maintaining high-resolution specifications — a truly "highly resolving" system. Read on and see how John's email clarifies the discussion with specifications and insights from a world class designer. Below is John's contribution to this important topic (reprinted here with his permission): Mark, It is not a matter of fancy cables, and esoteric tweaks. It is all about the math (MW bolded). If anyone hears the difference, it probably will not be on the basis of the frequency response. There are exactly three potential advantages provided by high-resolution audio: 1: An increased high frequency limit 2: An increased immunity to the clipping of intersample peaks 3: An increased SNR Items 2 and 3 are audible under the right circumstances. Item 1 may never or almost never be audible. Here is my reasoning: 1: High Frequency Limit Very few listeners will have transducers that extend beyond the 22 kHz limit of the CD format. The exception will be listeners with good headphones or very good speakers. But, most listeners can't hear beyond 20 kHz. You will need the rare combination of someone will excellent hearing beyond 22 kHz who is listening through good transducers. You will also need significant musical content above 22 kHz (at sufficient levels). This is going to be too small a group to be statistically significant. The size of this group is likely to be 0. You need to put some young but trained ears into some good headphones and play the right source material. 2: Clipping of intersample peaks The worst-case clipping is caused by a tone at 1/4 of the sample rate that is shifted 45 degrees relative to the sampling clock. This tone can reach 3.01 dB over 0 dBFS before the maximum digital codes are reached. This 0 dBFS + condition can happen 1000s of times on a single CD track. When upsampled in a sigma-delta D/A converter, these intersample peaks can cause clipping in the D/A converter. This often causes a DSP overload that creates a burst of IMD. This artifact is audible, but completely avoidable. The Benchmark DAC2 and DAC3 converters do not have this artifact at any sample rate. Most other D/A converters have this artifact. This will tend to make high sample rates sound better unless you are using Benchmark DAC2 or DAC3 converters. Here is a case where a better system makes all sample rates sound good. Most systems will make 44.1 sound worse than it should. 3: SNR: A few quick calculations will show that the listeners will need playback systems with at least an 87 dB SNR and they will need to play the audio at peak levels exceeding 93 dB SPL. Otherwise, it is mathematically impossible to hear the noise advantage of anything beyond 16 bits. If the listener's system has a playback SNR of 87 dB and it is playing at a peak SPL exceeding 93 dB, they would be listening for a very small 1 dB difference in the noise floor. If the listener's system has a much better SNR, then the task will be much easier (assuming they turn the volume up high enough the hear the 16-bit TPDF noise). If their system is absolute state of the art, it will have a 130 dB SNR. If they set 0 dBFS to 130 dB SPL, the 16-bit dither noise will be reproduced 37 dB above the threshold of hearing and would be very audible. On such a system, you could easily hear the differences in word lengths until you reach 23 bits. But, you would go deaf listening to the music unless the music had an unusually high crest factor or was recorded at a very low level. You would need to turn the system down to listen to the music. The more you turn it down, the less difference you will hear. Here is the math (nothing here that you do not already know): SNR in dB for a digital channel is (6.02*N)+1.76 measured over the entire Nyquist bandwidth of the channel. If the signal is TPDF dithered, subtract 4.77 dB Therefore, for TPDF channels we have: (6.02*N)+1.76-4.77=(6.02*N)-3.01 dB At 16 bits this gives 93.31 dB. We will round to 93 for the sake of discussion. In order for a listener to detect a difference on the basis of SNR, all three of the following conditions must be met: 1. The recorded noise must be lower than the channel noise of the 16-bit system (-93 dBFS). 2. The channel noise of the 16-bit system must be played at a level that exceeds 0 dB SPL. Therefore, the SPL at 0 dBFS must exceed 93 dB. 3. The noise produced by the playback system must not be more than 6 dB higher than that of the 16-bit system. This noise summation will produce just detectable noise difference of 1 dB. Therefore the SNR of the playback system must exceed 93-6 = 87 dB. Item 1: You are controlling item 1 with your choice of source material. Item 2: The listener may or may not choose to exceed a peak SPL of 93 dB during the test. The peak SPL chosen by listeners will be higher on uncompressed material due to the higher crest factor. You are choosing the source material and can experiment with different crest factors. Item 3: This is a big problem! Many "high-end" systems are not capable of delivering an 87 dB SNR. There are almost no speaker systems that can do better than about a 105 dB SNR because of amplifier limitations (the Benchmark AHB2 is a notable exception). A few state-of-the-art systems can deliver a 130 dB SNR to headphones if all of the components are properly gain staged (Benchmark DAC3 driving a Benchmark HPA4 is one example). A Benchmark AHB2 power amplifier driven by a Benchmark DAC3 can deliver a noise-free 130 dB SPL if it is driving speakers that have a sensitivity of at least 104 dB at 2.83 Vrms. We have a few customers with such systems, but there are less than 10 examples worldwide. Here is a chart that I created. It sums the digital channel with the playback system noise to calculate the SNR that will be delivered to the listener. I included bit depths of 8 through 24 bits. Find your playback SNR or peak playback SPL (whichever is lowest) on the X axis and then find the y value for each bit-depth curve. If the lines are separated at your SNR or SPL, then you will be able to hear a change in the noise floor. Example 1: If you have a noise-free playback level of 100 dB SPL (find 100 dB on the X axis), you should be able to hear changes for bit depths up to 19 bits. Beyond 19 bits, there will be no audible (or measurable) improvement. Example 2: If you have a system that can achieve a noise-free playback level 130 dB SPL, and you are playing it that loud, find 130 dB on the X axis. You should be able to hear the noise differences for bit depths up to 23 bits. Beyond 23 bits, there will be no audible (or measurable) improvement. Example 3: You have a system that has a SNR of 87 dB and you are playing it at a peak SPL of 100 dB. Take the lower of the two (87 dB) and find this on the X axis. Any bit depth above 16 bits will produce a 1 dB reduction in the noise relative to the 16-bit system. Longer word lengths may be just noticeable, but 17 bits will give the same performance as 24 bits. Example 4: 100 dB SNR playing at a peak level of only 80 dB. Find 80 dB on the X axis. Changes should be noticeable up to a bit depth of 14 bits. I should also note that a given D/A converter may deliver different performance at different sample rates. They often use entirely different filters and may have entirely different THD performance. The filters may have distinctly different phase response and this can be perceived as a change in frequency response. Early oversampled converters performed poorly at higher sample rates due to poor stop band attenuation. To mitigate this problem, I would suggest separating the word length tests from the sample rate tests. Change one parameter at time. Test 44.1/16 against 44.1/24. Then test 44.1/24 against 192/24. This will tell you if the audible differences are related to word length, sample rate or both. Once this has been established, you could look at 18, 20, and 22 bit depths to determine the threshold of audibility. You could also run a separate test to determine the audibility of sample rate is linked to intersample clipping or to bandwidth. John Siau
  4. Hi Alex, Apologies I just assumed it was you. Not sure why my name was on the quote regarding the files being uploaded? Not a big deal just weird.
  5. Ajax, would it be possible to hand ALL the original Hires to me by PM etc., so I can judge them for being genuine and / or not ruined ? I ask, because the chance anno 2019 is still a virtual zero that they are OK. Your list comprises just of too much to be all OK. Mind you, downconverts from multi channel are flawed by guarantee ... and you know your sources. So just saying ... Hi Peter, Not sure what is going on but that quote was from Alex (@Sandyk) not from me? i.e Alex uploaded files to his Dropbox
  6. Hi Hi Jud, Nice to hear from you. I hope you are enjoying your new home. My own renovations will be complete next month and my life should get back to normal. Tom Hank's "The Money Pit" has taken on a whole new meaning With regard to Hi Res I have a similar approach to yours, I've simply selected different experts being Mark Waldrep and John Siau. I'm not anti Hi Res as suggested by Alex, I'm simply sceptical, especially when it is open to manipulation by the likes of MQA. Mark has spent most of his career promoting the benefits of Hi Res but is now expressing some doubt of it's actual benefits. Hence the study and my promotion of it. in terms of experts Barry Diament has always maintained that 90% of the quality of the sound/music is determined before it leaves the microphones. He has selected 24/192 as his preferred format and believes that there is no need to go higher, whereas Mark Waldrep believes 24/96 to be sufficient, but is now second guessing that. John Siau believes 16/44.1 is sufficient assuming the DAC is property designed... it's just maths. George provided sound reasons (as have you) in his earlier comment why Hi Res is beneficial, however, can't they be overcome by well implemented noise shaping & dithering at the mastering end, and up sampling at the Software/ DAC end? For me personally CD quality just makes more sense as most of the music I listen to is either from the 70's and early 80's recorded to tape, or more recently music that has been heavily compressed. Both I believe are easily accommodated by CD's resolution. In a world where we all need to reduce our foot print shouldn't we strive for smaller data files not larger? For better or worst 16/44.1 was chosen as the benchmark by Sony & Phillips, accordingly the majority of music is in that format, should we not therefore focus our attention on better mastering of that format instead of allowing the marketing men to promote even greater and greater sample rates, whether PCM or DSD.
  7. Hi Alex, I've got a deal for you - I'll listen to Barry's Kay Sa if you agree to join Mark's Study and publish your results after he publishes his. Deal?
  8. Hi Alex, You don't need to convert me as I don't hold a firm position, however, I am very sceptical of the benefits touted about Hi Res. My personal experience is that well mastered 16/44.1 sounds very very good. About 4 years ago I purchased a Devialet 220 with OTHM G1 speakers, marketed as a complete system (Ensemble). I bought the demo system from a HiFi show in Melbourne where all the dealers were demonstrating using Hi Res and vinyl (Michael Fremer was presenting), except Devialet, who were using 16/44.1 .... and it sounded so much better. I asked the demonstrator why he wasn't using Hi Res material and he just nodded knowingly and basically told me it wasn't necessary. Surely you would use the best available material if you were selling a product? At that time 95% of my music was of CD quality, and the best streaming available was also CD quality, so it just made sense for me to purchase a system that played 16/44.1 well. I have a second system in my office, a Benchmark Media DAC / Preamp into Adam A7 active speakers. I am a great admirer of Benchmark, not only for it's technical excellence and service but also it's no bullshit approach, which is why I quoted John Siau (Director of Engineering) in my previous "Common Sense" thread. His position is very clear - it's just maths. Having said that the best sound I have ever heard (through any system using any format) was from Peter Gabriel's Society of Sound in 24/48 in my office. Was that due to the 24 bit rate and slightly higher sample rate, my room acoustics, or the location and quality of the microphones and excellent mastering? I don't know, but it was incredibly life like and natural sounding. I have degree in Engineering (Civil) although I have spent most of my life running small businesses. One thing that has always stuck in my mind from my time at University was to always strive to do more with less. i.e. don't waste materials for both commercial and ecological reasons. IF we can produce great sound with only 16/44.1 then it just makes sense to me not to burden our Broadband, LANs and hard drives with huge data files. Finally, I spent good deal of time corresponding with Barry Diament, when he was a regular contributor here. A terrific fellow and a thorough gentleman and obviously a very capable and experienced mastering engineer. Barry encouraged me to download his files in 16/44.1, 24/96 & 24/ 192. He was adamant that there were vast difference between each format. I spent a whole day listening but couldn't hear a difference between any of them. This could be due to my poor hearing from rock concerts and blasting my ears with headphones or simply old age (now 63) or there is no perceivable difference. That is why I am encouraging everyone to participate in Mark's study. The bigger the sample base the more reliable the results. All the best Ajax
  9. Hi Alex, Didn't take long - I wish it was that easy to catch something fishing. FWIW I do enjoy your contributions - takes two to tango! All the best, Ajax
  10. Hi Everyone, Following is an invitation to participate in a study being performed by Mark Waldrep to determine whether or not we can actually hear differences between various formats? I know this is an old and tired argument but one in my opinion that really needs to be put to bed and I encourage you to participate. Too may of us are being ripped off by manufactures' marketing hype, and too many potential audiophiles are staying away because we have overcomplicated things by looking for solutions to problems that simply don't exist. It takes courage to participate in these types of tests because you may have to face your biases and long held beliefs. Prior to reading the study please read the introduction to my previous thread on this subject "Some Commonsense" and in particular to John Siau of Benchmark Media's thoughts - it's all about the maths. The HD-Audio Challenge II Dr. AIX I spent the weekend gearing up for the second round of the HD-Audio challenge. Some of you may remember the first iteration of this study (click here). The music industry seems intent on continuing to push their claims that "hi-res audio" is a tremendous advance in the evolution of music reproduction. After being involved with real high-resolution audio for almost 20 years, I'm not so sure it matters. I'd love to demonstrate that hi-res music and hi-res audio are delivering a "better" experience, but the studies I've read have left me unconvinced. I believe that I can contribute to the debate by offering up a catalog of real high-resolution tracks in a variety of formats. You — my readers and fellow audiophiles — can download the tracks and play them to your heart's content. I only ask that you not analyze them to determine which is which. What's the point of cheating? I've selected 20 tracks from a variety of genres and took into consideration suggestions from many of you. I've included solos, small and large ensembles, acoustic and electric, and vocal vs. instrumental http://www.realhd-audio.com/?p=6197.The tracks that will be available are listed below: The HD-Audio Challenge II - Track List These are full length tracks not merely samples. I spent all weekend converting the tracks using Sonic Studio's professional software tool PROCESS to do the conversions. I took the native 96 kHz/24-bit PCM masters and downconverted them to 96 kHz/16-bit, 44.1 kHz/24-bits, and 44.1 kHz/16-bits (CD "Redbook" spec). I will also create constant bitrate MP3 versions at 320 and 256 kbps for those interested in compressed formats. Then I converted all of downconversions back to 96 kHz/24-bits so that all of them are precisely the same size. I have been very careful to ensure that they are the same volume. I have uploaded all of the files to a folder in my premium Dropbox account and will "Share" the contents with those interested in participating in the study. The files are randomly named and should provide a rich opportunity for those willing to download them and do some serious listening. The goal is to discover if bona fide high-resolution audio recordings can be distinguished from lower resolution formats. A Preview I will be doing a thorough analysis of each file and providing the spectra and dynamic analysis to participants. I've already done that for a test file by The Latin Jazz Trio. Here's the spectra of all of the formats: The Spectra of "Memories of Rio" in all six formats Sign Up The more audio enthusiasts that participate in this study, the more raw data I'll have and the more valid the results will be. I'm prepared to be criticized for the casual nature of this experiment. Some will insist that using my own catalog is too limiting, others will insist that it be done in a state-of-the-art studio, or with mega buck equipment. I don't believe that any of those things matter. We all have different rooms, systems of differing values, and varying abilities to listen...exactly the diversity that is required to establish whether the marketing claims made by the industry are true. If you want to sign up, you'll have to visit the post on my site and use the form at the bottom of the page by clicking here. This should be fun. I'll leave the files up for a couple of months. I have to report back to my university sometime in early 2020, so you'll have lots of time. Thanks!
  11. Hi Ralf, FYI a used AHB2 sold last year on Canuk Audio Mart for CAD $2600 (= $US 1950). When you consider the AHB2'S performance specification, excellent reviews and Benchmark's reputation for quality engineering that is surely a bargain. https://www.canuckaudiomart.com/details/649438645-benchmark-abh2-power-amplifier/ I note that on HiFi Shark there is currently one for sale at $US2600. https://www.hifishark.com/search?q=benchmark+ahb2 I have a DAC1 HDR, which is I purchased new in 2010 for $US1800, and a DAC2, which I purchased second hand this year for US $900. I can't speak highly enough of Benchmark gear, whether new or second hand. All the best, Ajax
  12. Hi PAR, FYI the Society of Sound recordings, a joint venture between Peter Gabriele and B & W speakers, were originally distributed at 24/48 and sounded amazing. Their files were available as downloads and you received 12 albums of "new" artists for 50 GBP. It was Gabriel's way of giving back by helping new artists get a start. Good bloke. The several albums I received were very good in terms of the music, however, the sound quality was simply stunning, certainly the best recorded sound I have heard to this day. I'll never forget my then 12 year old son coming into my home office one night and exclaiming "that's spooky Dad, it's like she's in the room with us". At that time (about 2011) their web site quoted an English professor in psychoacoustics who stated that the bit rate was more important than the sample rate, however, I note more recently they have increased the sample rate to 96. I assume as you suggest that their ADC equipment was capable of 96, and with the increase in bandwidth and better internet speeds why not take out some "insurance" and ensure they left nothing on the table, however, from what I was hearing through my then Benchmark DAC1 and ADAM A7 active speakers, I doubt it was really necessary.
  13. Hi Chris, Didn't know you had Benchmark gear. Many many years ago I thought you did a review of the original Benchmark DAC 1 and added it in your CASH list. It's not there anymore so did I imagine it? Are you planning a review of the DAC3? Apologies for the off topic but I just bought 2 x DAC2s for less than US$1,000 each. Best HiFi bargain going around in my very humble opinion.
  14. Thanks Ralf, I wasn't a big fan as a young man and actually appreciate his early Cars' music more today. Great beats and licks that are fun with plenty of drive, that contrast with the clever but self deprecating lyrics.
  15. Thanks Chris, I thought your review was well balanced and thoughtful , you give credit where credit's due, as well as highlighting Neil's lack of technical understanding of how digital audio actually works. I've been listening to Neil's music for many many years, since I was a young boy in the late 60's, and what consistently shines through is his desire for authenticity, to be real, and I disagree with earlier contributors that suggest he was in Pono only to make money. Neil is an artist, an idealist and above all a humanitarian. His very nature makes him exactly the wrong person to take the lead in such a demanding project. I think you hit the nail on the head when you cited problems started when John Hamm's influence was replaced by Bob Stuart's. The record companies' profits have been decimated, first by Napster, then by Apple and finally by the streaming companies and their desperation to wrestle back control is a large part of the reason why MQA has enjoyed it's (limited) success to date. I think the whole pono fiasco highlights Neil's imperfections (an idealist surrounding himself with mates and not professionals) as well as his attributes, trying in his own way to create a better music industry. His contribution to music cannot be underestimated and his efforts to provide consumers with better sounding music (I can't stomach the expression "hi-res", it's a nonsense to me) should be applauded. At the very least he had a go at fixing what he saw was a wrong where others merely whinged, unfortunately, when Hamm went it was always going to end badly.
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