robert_kc

Are you saying that one factor that can cause two modern amps to sound different is "input impedance vs frequency and output impedance vs frequency". (I'm not a technical expert, so additional information would be helpful.) If so, does the "Richard Clark $10,000 Amplifier Challenge" attempt to mask these inherent differences in 2 amps by inserting an equalizer into the audio chain of one amp?

Here's the opening statement from wikipedia re ABX: An ABX test is a method of comparing two choices of sensory stimuli to identify detectable differences between them. A subject is presented with two known samples (sample A, the first reference, and sample B, the second reference) followed by one unknown sample X that is randomly selected from either A or B. My earlier questions stand:

If you're not sure about the meaning of this: The rules for the "Richard Clark $10,000 Amplifier Challenge" also state: "Compensation will also be made for input and output loading that affects frequency response." Then, why did you say this:

I'll repeat the question I asked earlier: The rules for the "Richard Clark $10,000 Amplifier Challenge" also state: "Compensation will also be made for input and output loading that affects frequency response." What does this mean?

Late at night when I can't sleep, I sometimes listen to the mono system in my bedroom, and it sounds very pleasant at low/moderate volume: The speaker is a single Klipsch WF-35. Source is an older CD player. Fisher TA 500 (1950s era AM/FM mono tube receiver).

If you already own (or have access to) 2 stereo amps and 2 sets of speakers, you can cobble together a proof-of-concept system to determine if surround-sound suits you. You don’t need an AVR (or pre-processor) to play multi-channel digital recordings (e.g., SACD, Pure Audio Blu-ray, and Blu-ray video). An Oppo universal player (e.g. UDP-205, BDP-105, or BDP-95) will decode any digital recording. These Oppo players have built-in "pre-amp" functionality, including selectable downmixing (e.g., 7.1, 5.1, 5.0, 2.1, 2.0), bass management (i.e., configurable subwoofer crossover and RCA line-level connection), and remote volume control. Additionally, you can simply not connect the rear channels and have 3.0 or 3.1, or combine the rear channels for 4.0 or 4.1. You can build a great surround sound system with an Oppo universal player and two stereo amps and speakers (i.e., 4.0 or 4.1 system). If you’re interested in experimenting with this, I suggest that you conduct a test by connecting a stereo amp and speakers to the Oppo's Surround Left and Surround Right outputs and listen for how much rear content there is in your favorite recordings, and how much L vs. R distinction. Only you can decide if separate L&R rear channels are worthwhile. (For the classical music I listen to, there is little rear channel sound (basically hall sound) and little L vs. R distinction. I therefore combine Surround Left and Surround Right.) If L vs R distinction isn’t important to you for the rear channels, then combine the rear channel connections from the Blu-ray player into one via an RCA Y-cable. Connect one stereo amp for L&R, and a second stereo amp for center and rear. (Of course, you could implement 5.1 by using two stereo amps plus one mono amp.) I use the Oppo's analog line-level RCA connections to my vintage tube amps - in other words using the Oppo's DACs and pre-amp. In my 4.2 system, L, C, and R speakers are Klipsch RF-7II. The single rear speaker is an RF-7. Subwoofers: SVS SB16-Ultra, Klipsch R-115SW. I use whatever tube amps I choose. For example, yesterday I listened to a classical Blu-ray using a Scott 296 for front L&R, and a Scott 272 for center and rear. Sounded fabulous.

miketn, Impressive looking set-up. I'm jealous. I wish I had room for Jubilee. I haven't even heard them.

I don't discount that electronic components might "burn in", however I think it's at least as much of a factor for your ears/brain to adjust (within limits).

I have 3 systems that work well for movies and music. IME the relevance of surround-sound depends on room layout, and genre of music. Room layout. IME, when the main speakers must be far apart due to room layout, then a center channel is useful. Also, part of the “live-concert-hall experience” for large-scale orchestral music isn’t just the surround, it’s the amount of acoustic power. If in the same size room, you have quantity of 3 identical speakers (left, center, right), you’ll have more acoustic power than 2 speakers. Genre of music. Hi-res surround-sound recordings (SACD (audio-only), Pure Audio Blu-ray (audio-only), DSD downloads (audio only), Blu-ray (audio/video), and Ultra HD Blu-ray (audio/video)) are commonly available for classical, opera and ballet, and are capable of fabulous sound. (Blu-ray audio/video classical concert recordings are becoming common, and box sets (e.g., all symphonies by a composer) are often a great value.) I use Oppo universal players (UDP-205 x 2, BDP-105, BDP-95) that effectively have the pre-processor, bass management (i.e., RCA line-level subwoofer connection), and multi-channel DAC built-in. In other words, the Oppo players have RCA line-level connections for 2.0, 2.1, and 5.1. I can connect vintage tube amps direct to the Oppo players. I have 3 systems that serve double duty for movies and music: One 4.2 system. Front, center, and left speakers are Klipsch RF-7 II. A single rear speaker is a Klipsch RF-7. (Y cable from Oppo UDP-205 combines Surround L and Surround R. Oppo confirmed that this arrangement is OK.) Multiple tube amps. I connect one stereo tube amp for front L&R, plus a second tube amp for center and rear. Two subs connected via RCA Y cable to Oppo. (SVS SB16-Ultra, Klipsch R-115SW.) For stereo source material, there is no compromise in audio quality when played as stereo – except that in this system the speakers are somewhat far apart. (Or, I can engage the Oppo’s DTS Neo:6 feature to generate pseudo center-channel and rear content, but I generally don’t want DSPs “mucking around” with the classical music I love.) For classical recordings that feature surround-sound, I realize excellent sound quality via my tube amps. Two 2.1 systems. Speakers are close enough (5 feet apart) that there is no “hole” that needs to be filled in (i.e., no need for a center channel). For Blu-ray movies, I use the stereo track, and dialog is mixed into the L&R speakers. Each of these systems has multiple tube amps, plus one solid-state amps for movies. In both systems the large tower speakers and subwoofer deliver excellent sound quality. In my 4 systems with multiple amps, I use patch panels (banana plugs) to enable me to connect the speakers to whichever amp I choose. I use a Niles AXP-1 RCA selector switch to connect the Oppo to the amp (except in my surround-sound system where I use F/F RCA cables). These systems work well for both movies and music. For the classical music I love, I have the minimum number of components (and DSPs) in the music chain. I can directly connect my vintage tube amps (e.g., a pair of MC30s) to my Oppo UDP-205 (i.e., no pre-amp, no pre-processor, no AVR, no outboard electronic crossover, etc). For movies I generally use a solid-state amp, in order to save hours on the tubes.

The rules for the "Richard Clark $10,000 Amplifier Challenge" also state: "Compensation will also be made for input and output loading that affects frequency response." What does this mean? In what percentage of tests where there was a difference in sound between amps did he apply EQ in order to make the 2 amps sound similar?

Have the questions I posed in an earlier post about ABX tests for audio been answered? Can most people listen to 2 different music samples (A & B ) that have subtle sound differences, and then listen to Sample X, and reliably identify whether A or B is the same as X? What percentage of the general population can remember 3 audio samples that have subtle differences? What percentage of trained listeners? What are the limits of human memory of sound? If someone can’t identify X as A or B, does that mean that A & B are the same, or does this show that people can’t remember 3 sound samples with subtle differences, and the ABX test is therefore limited in its usefulness for audio? (It seems to me this may be different from a scenario where the differences between A & B are significant, e.g., A is a duck quacking and B is a dog barking.) Is an ABX audio test effectively a shell game – i.e., it confuses people? What is the explanation for the phenomenon that many people who participate in formal tests (e.g., ABX, DBT) often cannot reliably identify subtle differences in sound quality (e.g., between different amps, or different bit rates for recordings), whereas many life-long hobbyists report that they can readily hear differences via their casual listening observations? Are the hobbyists “audiophools”? Or does this point to a problem with the test methodology? I don’t know the answers to these questions, but clearly there is a disconnect between some ABX audio test results and the experience of many life-long hobbyists.

In other words, if 2 amps sound different, then he’ll insert an equalizer to make them sound similar. It appears that the test was rigged to make the amps sound similar enough that the listener can’t pass the ABX challenge.

I understand that your assessment is that there is no audible difference between hi-res recordings delivered at 24bit/192kHz vs. 24bit/96kHz (which are both considered hi-res deliverables). Based on your experience, do you think that hi-res recordings delivered at 24bit/96kHz sound better than the same recording down-converted to CD (16bit/44.1kHz)?

We’re in agreement about garbage-in/garbage-out. Of course, the hotly contested issue is this: If a modern top-quality recording was recorded and mastered in 24bit/192kHz, will most audiophiles hear a difference between a 24bit/192kHz deliverable (e.g., 24/192 FLAC download or Pure Audio Blu-ray disc) vs. that recording down-sampled to fit on a CD (16bit/44.1kHz). (A separate question is whether John Q. Public would hear a difference listening via their “big-box store” hi-fi system.) Could I pass a double-blind listening test? I don’t know, and frankly I don’t care about the results of blind listening tests. IME modern hi-res classical recordings usually deliver excellent audio quality. My perspective is this: I own Oppo UDP-205 universal players that can play any digital audio format, so why not acquire the recording in the format it as mastered in, vs. down-sampling the recording to fit on 30+ year-old storage technology (i.e. CD). A Blu-ray disc is the same size as a CD, and holds vastly more data. Even if the difference in sound quality between hi-res and CD is subtle, when I listen to the classical music that I love I want the best recording quality available. And, I enjoy surround-sound in my basement hi-fi system. (IME, when the main speakers must be far apart due to room layout, then a center channel is useful.) With modern hi-res surround-sound classical recordings and my favorite tube amps and Klipsch speakers, I’m able to achieve a near “live symphony hall” experience. Moreover, in a growing number of cases modern classical recordings feature video. Here’s an example of a Blu-ray audio/video box set that I enjoy: Rafael Frühbeck de Burgos Danish NSO Ludwig van Beethoven: Symphonies Nos. 1–9 Joaquín Rodrigo: Concierto de Aranjuez Hector Berlioz: Symphonie fantastique, Op. 14 Richard Strauss: Eine Alpensinfonie (An Alpine Symphony), Op. 64, TrV 233 IIRC, I paid $50 for this box set, which I think is a very reasonable price. I also have Blu-ray audio/video box sets of symphonies by several other composers. And, as I said earlier, hi-def video is indispensable for ballet and opera (i.e., these are visual art forms as well as music). And with a Blu-ray recording of an opera, the libretto is displayed on the screen, so I don’t have to turn the lights on and use reading glasses to read a printed libretto (which is what I have to do when listening to CD recordings of opera). As I said earlier, music genre is a factor in the relevance of modern hi-res surround-sound recordings. For the classical music I love, my first choice for media is Blu-ray audio/video. (Ultra HD Blu-ray classical recordings are starting to become available.) My second choice, SACD and Pure Audio Blu-ray that feature surround-sound. My third choice, hi-res (e.g., 24bit/96kHz or 24bit/192kHz) stereo FLAC download. My advice to newbies: Consider the fact that there are new ways to enjoy music (compared with CDs), and consider that the sound quality of your hi-fi system is limited by the quality of recordings you play.

I agree that copying a relatively "low-res" recording into a 24/192 FLAC file is pointless. You expressed this point better than I did: "They just took a gallon of music and poured it into a 55 gallon drum, but it's still only a gallon. " My writing may not have been clear. That's what I meant when I said: "It’s important to point out a distinction. There are still people who copy a CD to their PC, convert it to 24bit/96kHz FLAC and say: “I don’t hear a difference”. Or they’ll buy a decades old recording that has been remastered and say: “I don’t hear a difference”. Garbage-in/garbage-out. The critical issue is provenance – i.e., high quality throughout the entire recording and delivery chain." " ... if someone only listens to recordings that are several decades old, then they’re stuck with what WAS state-of-the art recording technology several decades ago. (Caveat: as discussed in my last post, some good quality vintage analog master tapes have been digitized in hi-res, remastered, and delivered in hi-res, sometimes with fairly good results. But IME generally not as good as modern high-quality hi-res recordings.)"

Sorry, I don’t understand your point. If it helps to clarify my opinion, I’ll offer newbies the same advice regarding the “hi-res controversy” that I offered regarding the “amplifier controversy”: listen for yourself and decide for yourself.

An AVR is not needed for multi-channel. I use Oppo universal players (UDP-205 x 2, BDP-105, BDP-95) that effectively have the pre-processor, bass management (i.e., RCA line-level subwoofer connection), and multi-channel DAC built-in. In other words, the Oppo players have RCA line-level connections for 2.0, 2.1, and 5.1. I use vintage tube amps. I recognize that John Q. Public will buy an AVR from the big-box store, but as I've said before, this is a hi-fi hobbyist forum, so I thought I'd offer a different perspective. IME, modern multi-channel (i.e., surround-sound) hi-res classical recordings, tube amps, and Klipsch speakers work well together. Just my 2 cents ... 😊

Another topic that is hotly debated. Have you listened to high-res deliverables (e.g., SACD, Blu-ray, hi-res download) for recordings that have hi-res provenance (i.e., recorded and mastered in hi-res)? If you can’t hear a difference – then OK. (Some people reportedly can’t hear a difference in amps.) C'est la vie. To each their own. It’s important to point out a distinction. There are still people who copy a CD to their PC, convert it to 24bit/96kHz FLAC and say: “I don’t hear a difference”. Or they’ll buy a decades old recording that has been remastered and say: “I don’t hear a difference”. Garbage-in/garbage-out. The critical issue is provenance – i.e., high quality throughout the entire recording and delivery chain. All new classical music recordings are recorded and mastered in hi-res, and almost all are available in a hi-res consumer deliverable (i.e., SACD, Pure Audio Blu-ray, Blu-ray, Ultra HD Blu-ray or hi-res download). And I find that these usually have excellent audio quality, and I enjoy them immensely. Moreover, modern classical recordings almost always offer surround-sound (in addition to a stereo track), and sometimes have hi-def video. Video is essential to ballet and opera, and IMO very enjoyable for classical concerts. And Blu-ray is capable of displaying an opera’s libretto on the screen, which is extremely useful. And Blu-ray has much greater storage capacity compared with the same size CD disc. Bottom line, newer technologies have capabilities that CDs can’t deliver. The assertion that people can’t hear the difference between CD and hi-res in a double-blind test is like the assertion that people can’t hear the difference in amps in a double-blind test. We’ll be here for another 50 pages debating it … If a modern recording is recorded and mastered at 24bit/192kHz, why would you buy a consumer deliverable that has been down-sampled into 30+ year-old storage technology (i.e., 16bit/44.1kHz Redbook CD), vs. buying the recording in its native format (e.g., Pure Audio Blu-ray disc or 24/192 FLAC download)? Similarly, if the recording was captured in hi-res DSD – why not buy the SACD or DSD download, vs. transcoding it and down-sampling it into 16bit/44.1kHz PCM (i.e. CD)? SACD, Blu-ray, and hi-res downloads are mature, well established technologies. For the music I enjoy (classical) there is a wealth of modern recordings in hi-res, with new hi-res recordings available every month. OTOH, if someone only listens to recordings that are several decades old, then they’re stuck with what WAS state-of-the art recording technology several decades ago. (Caveat: as discussed in my last post, some good quality vintage analog master tapes have been digitized in hi-res, remastered, and delivered in hi-res, sometimes with fairly good results. But IME generally not as good as modern high-quality hi-res recordings.) Music genre is a major factor in the relevance of hi-res recordings. For the classical music I love, hi-res is highly relevant.

Yes, I agree that some vintage recordings sound surprisingly good – but IMO not as good as the best state-of-the-art modern recordings. I own a number of the RCA Living Stereo classical recordings from the 1950s that were remastered from the original analog tapes (in some cases 3 channel) and delivered on SACD. One of my favorites: (I also occasionally enjoy my 1950s mono LP of this recording.) I also have at least one Mercury Living Presence classical SACD that was remastered from the original 3 channel 35mm magnetic tape that was recorded in 1962, and it sounds surprisingly good considering the vintage. And I have the following performance from the 1980s that was captured on 35mm film, and then remastered in Blu-ray format. Both audio and video are surprisingly good considering the vintage. I occasionally enjoy this re-mastered SACD of Furtwangler’s Beethoven 9 from 1954. This is the oldest recording in my collection that I tolerate in terms of audio quality. (On the other hand, I don’t routinely listen to the famous 1942 Furtwangler recording – to my ears the sound is intolerable.) I find that some recordings from the early days of DDD (mid 1980s) are unlistenable. To me, the violins in my 1983 CD of Berstein’s recording of Barber’s Adagio for Strings sound so harsh that it’s unbearable. On the other hand, my modern hi-resolution digital recording of Barber’s Adagio by the Dogma Chamber Orchestra has no trace of harshness, and for me this definitely tips the balance in favor of the modern recording. Bottom line, IMO none of the remastered vintage recordings has audio quality equal to the best modern hi-res recordings. And, unfortunately, IMO many vintage recordings have intolerably poor audio quality. Classical music lovers often must decide which is more important: performance quality, or audio quality of a recording. I’m not a music scholar, and I’m not hyper-critical of a performance. However, I have no tolerance for poor audio quality. My favorite format for classical music is Blu-ray audio/video. (A few Ultra HD Blu-ray videos are becoming available.) My second choice are hi-res audio-only recordings that feature surround-sound (i.e., SACD, Pure Audio Blu-ray). My third choice is stereo 24/96 or 24-192 FLAC downloads. Of course, these are just my opinions.

I would never criticize someone else’s choice of music. Music is deeply personal. People are different. I respect that. It is not my intent to ruffle any feathers with what I’m about to say. At issue IMO is what types or recordings are more likely to highlight subtle differences in hi-fi systems. With a few exceptions, it seems to me that most of the recordings by most of the artists you listed would be “vintage recordings”. Again, I respect different peoples’ choices in music. With that said, it seems to me that: The subtle differences in amps would be more apparent when playing modern hi-res recordings, vs. vintage recordings. By “modern hi-res recordings” I mean recordings that were captured and mastered in hi-res (i.e., 24bit/192kHz PCM, or DSD), and delivered in a hi-res format (e.g., SACD, Pure Audio Blu-ray, Blu-ray, Ultra HD Blu-ray, 24bit/192kHz download, or DSD download). (In contrast Redbook CD is 16bit/44.1kHz.) FWIW, I own some older classical recordings because classical aficionados rave about the performance (e.g., Maria Callas), but the audio quality is poor by modern standards. IMO vintage recordings provide a poor basis for comparing hi-fi systems – even if these recordings have been remastered and delivered as 24bit/96kHz FLAC downloads (as is the case with Callas’ studio recordings). Garbage-in/garbage-out. You can’t make a silk purse from a sow’s ear - and a sow’s ear provides a poor basis for evaluating the sound quality of a hi-fi system. How can you conclude with confidence that distortion is being introduced by your hi-fi system, or if the distortion is in the recording - unless you have a top-quality state-of-the-art recording? Some music genres IME are inherently more demanding of a hi-fi system than others. For example, I have a few CDs by Eva Cassidy that sound good on almost any hi-fi configuration, because this music is not very demanding of the playback system. Tony Bennett is another example. (For example, my single-ended-pentode amp can easily handle these types of music, and sounds great doing so.) At the other extreme, a modern hi-res recording of Mahler Symphony 2 is much more demanding of the playback system. (Consider the dynamic range between the opening of the 4th and 5th movements, and consider the complexity of sound that ranges from a solo soprano to approximately 100 musicians playing fff.) IMO, a hi-fi system should excel at reproducing a folk singer (male and female) with an acoustic guitar, AND excel at reproducing a symphony orchestra. And swing with a big band. As I’ve discussed in previous posts, IMO the subtle differences in amps are more apparent for natural music such as classical, because there is a clear benchmark for sound quality (i.e., a live classical performance). We know how natural instruments (e.g., viola, clarinet) sound. If a hi-fi system makes violins sound harsh, it is immediately apparent. (OTOH, how do you tell if a deliberately distorted electric guitar sounds harsh?) And large scale orchestral music has a range of instruments that must be reproduced convincingly, including brass, woodwinds, stringed instruments, percussion, piano, organ, etc.. Which takes me back to my question: Have you performed your listening tests with modern top-quality state-of-the-art recordings (i.e., recorded, mastered, and delivered in hi-res) of music for which there is a clear benchmark for audio quality? How much demand was placed on the hi-fi system by the music you chose (e.g., simple folk music vs. large scale orchestral music)? Again, I’m not being critical of your music choices, and it is not my intent to tell anyone else what types of music to listen to. I’m just trying to understand why you can’t hear differences in amps.

Respectfully, I suggest that you re-read my post. I did not “entirely denounce this test”. I said: “IMO, more research is needed to answer why there is a disconnect between what some listening tests appear to show (i.e., no difference in amps), compared with the fact that many experienced hobbyists report that they hear differences." “It seems to me that this dilemma is something that scientists should investigate.” I think that your characterization of my post as dismissive is unfounded, and unfair. P.S. What does pharma have to do with the price of rice in China?

When you conducted your listening comparisons that caused you to conclude that “all modern amps sound the same”, were you listening to recordings “from the early age of stereo”? Or, were you listening to modern recordings that were captured and mastered in hi-res (i.e., 24bit/192kHz PCM, or DSD), and delivered in a hi-res format (e.g., SACD, Pure Audio Blu-ray, Blu-ray, Ultra HD Blu-ray, 24/192 download, or DSD download)? What type of player did you use to play the music files? In other words, have you performed your listening tests with top-quality state-of-the-art recordings and play-back gear? Or, are your conclusions based on listening to 50 year-old recordings? What genre of music was played during your listening tests? Music for which there is a clear benchmark for quality (e.g., classical), or not (e.g., disco)?

I believe this is prima facie evidence that “something is rotten in Denmark”. As I said in an earlier post, IMO this raises the question as to which listening test methodologies (that apparently are borrowed from completely unrelated fields such as pharma) are reliable when used to judge the quality of audio from a hi-fi system? https://community.klipsch.com/index.php?/topic/180949-advice-for-beginners-consider-this-test-from-an-audio-club/&do=findComment&comment=2342444 And as @Tizman pointed out in the previous post, bias cuts both ways. BTW, I mean this as no disrespect for the hobbyists in Guadalajara, Spain. It sounds like they had an enjoyable get-together. (And to illustrate my belief that people around the world really aren’t all that different, the hi-fi hobbyists in Spain refer to “WAF”.) With that said, it seems to me that using CDs vs. hi-res recordings, and some testers listening to disco music, using fairly wimpy speakers, results in a test that may not be particularly discriminating. I think the real issue is the effectiveness of various methodologies for hi-fi listening tests. Bottom line, IMO, more research is needed to answer why there is a disconnect between what some listening tests appear to show (i.e., no difference in amps), compared with the fact that many experienced hobbyists report that they hear differences. It seems to me that this dilemma is something that scientists should investigate.

There are several threads relevant to this topic, so I apologize if I’m repeating myself. Here’s a brief summary of what I think are relevant issues: Those of us who listen to “natural” music (e.g., classical) know how a live performance should sound - i.e., natural instruments (e.g., violins, trumpets) performing live in the intended venue (e.g., symphony hall, opera house, perhaps a church with acoustics suitable for chamber music) where no electronics are employed (i.e., no sound reinforcement system), and the recording is not deliberately distorted using electronic tools. For the purpose of defining a benchmark for how classical music reproduced in the home “should” sound, IMO the “work of art” – and the benchmark - is the live performance. (“Work of art” may mean something different in intellectual property law.) My goal is for the sound reproduced by my hi-fi system to remind me of the live performance, and for inevitable distortions to sound pleasant vs. unpleasant. (Of course, a limitation of my approach is that it relies on my memory. And I recognize that different venues have different acoustics.) OTOH, a lot of music doesn’t involve natural instruments, and in some cases there never was a live performance, and/or the sound was electronically altered – so it seems to me that the benchmark isn’t as clear for how such music “should” sound. (For a lengthier discussion of this, please see the threads referenced below.) I am not a recording engineer. With that said, it seems to me that “Audio’s Circle of Confusion” is more of a problem for the second category (i.e., electronically produced and altered music), and less of a problem the first category (i.e., natural music) – at least from the perspective of the consumer. In other words, the consumer is less likely to be “confused” (or uncertain) about how classical music “should” sound, compared with electronically altered music. (I’m not suggesting that the recording engineer’s job of faithfully capturing the live performance of classical music is easy. Undoubtedly the recording process is much more complex than I’ll ever understand.) Your thoughts? Following are links to my lengthier comments on these issues. FWIW, I’d be interested in further discussion about this.

It seems to me that the unanswered question is this: Does ABX testing yield meaningful results for the sound quality from a hi-fi system? I believe this is a separate issue from the usefulness of ABX testing for completely unrelated types of tests (i.e., not audio related) in completely unrelated fields (e.g., pharma)? I understand that no one may be able (currently) to answer the following questions. Is anyone who is reading this thread from an organization that is equipped to investigate questions such as: Can most people listen to 2 different music samples (A & B ) that have subtle sound differences, and then listen to Sample X, and reliably identify whether A or B is the same as X? What percentage of the general population can remember 3 audio samples? What percentage of trained listeners? What are the limits of human memory of sound? How to explain the phenomenon that many people who participate in formal tests (e.g., ABX, DBT) cannot reliably identify differences in sound quality (e.g., different amps, or different bit rates for recordings), whereas many life-long hobbyists report that they can readily hear differences via their casual listening observations? I don’t have the answer to these questions. I’m just saying that I think it would be useful to science, and the hi-fi industry, for these questions to be investigated by a qualified professional services organization that is well equipped to do so.