Digital Processor Reviews

Arvus H2-4D multichannel Dolby Atmos digital processor Page 2

Moving to music that is already familiar in multichannel, Morten Lindberg's magnificent recording of Arnesen's Magnificat (2L-106, SACD/Blu-ray), the Atmos rendition adds, in my recently revised system, four height channels to the SACD's already immersive mix, but it lacks the fine-spun detail of the SACD. Yet the streamed Atmos rendition delivered through the H2-4D was even more breathtaking than the SACD due entirely to its superior recreation of the Nidaros Cathedral acoustic. While the SACD presents chorus, orchestra, and organ all around, the Atmos version fills the listening space with a convincing envelopment. It's thrilling despite the lossy medium.

I wanted to hear Atmos content from the Berlin Philharmonic's Digital Concert Hall. It's one of my favorite music resources, and it has embraced Dolby Atmos (footnote 9). At first, I hit a snag: I couldn't access Atmos with their desktop streaming app because it is accessible only via Apple hardware and Apple's Safari browser; I live in Windows world. Fortunately, I was able to load the Digital Concert Hall app on my AppleTV 4K. Lo and behold: a new library of recorded live concerts in Atmos!

Playing them in Atmos through the Arvus, I was impressed with their consistency. My favorite so far is a BPO concert from December 22, 2022, with Vikingur Olafsson at the piano and Santu-Matias Rouvali conducting works by Salonen, Adams, Bach, and Prokofiev. Of the four pieces on the program, one in particular—Prokofiev's Symphony No.5 in B flat major—clearly demonstrates what Atmos has to offer. Despite the lossy, 48kHz constraint, the H2-4D delivered balance and clarity with good soundstage detail, all within the acoustic space of the Berliner Philharmonie. Begin with the polite applause that accompanies Rouvali's entry, and don't be timid: Turn the volume up. The symphony starts with an Andante that's appropriately gentle, but an intensifying development section builds to the staggering coda, with its emphatic tam-tam. By the time you reach this point, you will feel that you're hearing the full orchestra at what seems like concert levels. That illusion is achieved not because Atmos has injected another 200Wpc into your system but because those immersive enhancements have convinced your ears that you are in the concert hall.

Multichannel discs with the H2-4D
If you thought streaming via Arvus from the AppleTV+ was easy (once the Atmos system was assembled), playing Atmos and other "immersive" formats from Blu-ray discs is a piece of cake. Plus, it comes with the bonus of truly lossless 48kHz audio. I selected my Oppo BDP-105's HDMI output with the Marantz switch, popped in a Blu-ray disc, and navigated the menu with the Oppo's remote control. The H2-4D displayed "Dolby Atmos (Dolby TruHD)," although still at 48kHz.

First up: a much-praised disc that had already shown me, via 5.1, how inadequate two-channel stereo is to resolve musical detail in recordings made in highly reverberant venues. Lost Voices of Hagia Sophia, with Alexander Lingas and Capella Romana (Capella Romana CR420-CDBR), is actually a studio performance that has been digitally enhanced to recreate a performance in the domed Hagia Sophia Grand Mosque in Istanbul. In stereo, the voices were indistinct and seemed to swim in the lively acoustic. Multichannel added specificity to the ambience and definition to the voices. The Atmos tracks provided a much more realistic experience than stereo—even than 5.1—in that the distance between the listener and individual (and group) voices was specific with Atmos, defined not just by level or the degree to which the voices became lost in the ambience but as if the musicians and the listener truly were sharing the same space. A true immersive experience.

I bought Yello's much anticipated 14th album, Point (Blu-ray, Polydor 06024 3551161 0) in anticipation of the arrival of the Arvus H2-4D. Point is an enjoyable, playful mélange of rhythms and sounds bounced around in three dimensions. Riffs and details popped up where I didn't expect them. The effects were often startling and always entertaining. As music I didn't find it all that interesting, but it is fun enough that I expect it to grow on me as I listen more.

Overall, though, disc playback with the Arvus H2-4D is more satisfying than streaming because the user interface is more coherent. Discs also permit easy comparison of Atmos with higher-resolution multichannel formats.

The 2L label has released many recordings that include both an SACD with discrete multichannel tracks and a Blu-ray disc with Dolby Atmos (48kHz), 5.1 DTS HD MA (24/192), 7.1.4 Auro-3D (96kHz)—even 5.1 Dolby TruHD (24/192). Since the Arvus does not play DSD or render Auro-3D (footnote 10), I chose to focus my listening on how Dolby Atmos (48kHz) sounds different from 5.1 DTS HD MA (192kHz) and 5.1 Dolby TruHD (192kHz), all lossless.

Atmos and Dolby TruHD versions are found on Stale Kleiberg: Concertos, with Marianne Thorsen, Fredrik Sjolin, Eivind Ringstad, Peter Szilvay, and the Trondheim Symphony Orchestra (2L 2L-166-SABD). With Atmos, the soundstage expanded vertically and horizontally. I heard a consistent, albeit small, advantage in inner detail with the higher-resolution TruHD. More important than either of those differences is the contrast between Atmos's "you are there" presentation and the "they are here" presentation of the discrete multichannel experience.

I had a similar response to the Atmos and DTS HD MA versions of Ole Bull – Stages of Life, with Annar Follesø, Wolfgang Plagge, Eun Sun Kim, and the Norwegian Radio Orchestra (2L 2L-159-SABD). Higher resolutions confer an advantage, but the more-immersive Atmos has undeniable appeal.

Playing local Atmos files with the H2-4D
As of now, Dolby does not offer an Atmos renderer as a consumer software product (footnote 11); thus, for now, the Arvus H2-4D is the simplest, most direct way to play Atmos files. This is straightforward with Macs, but for Windows users (including me) there's a small complication: We must download the Dolby Access app (footnote 12) from the Microsoft Store and install it. Once I did that, I was able to play the IAA Sonic Brand & Dolby Atmos Channel Test in MP4 format (footnote 13), using JRiver to confirm my speaker/channel layout. So far so good—but I did struggle getting JRiver to work with some files in MKV Video and other formats. Rather than delay this review, I switched from JRiver to the VLC media player, which seems to play anything.

Now I was able to access the Spatial Audio Calibration Toolkit, downloaded from spatialcd.com. The toolkit is invaluable for anyone setting up an Atmos system, providing a wide array of tests and calibrations for perceptual evaluation and measurement with a calibrated mike and Room EQ Wizard. Setting levels, timing, polarity, and bass management can be a bear if you're not using an AVR or pre/pro, but the toolkit makes the process at least coherent.

I finally got to play some files, downloaded from the 2L and TRPTK websites. Recordings from both labels capture the ambience of the performance space, but they do it somewhat differently. Tuvayhun (2L 2L-171) is a delicate, moving, multimovement work by Kim André Arnesen for voices, solo instruments, and small orchestra, performed in the same Nidaros Cathedral as Arnesen's much larger Magnificat. Playing the Atmos file through the Arvus, the cathedral's vast space dominates our attention in what's probably an accurate representation of how this small ensemble really sounded in that space; it certainly was convincing. Switching to the 5.1 DTS MD MA (24/192) file, I felt a closer connection to the performers, probably as a result of the obvious reduction in ambience, although the higher resolution may also be a factor. These differences seem mostly attributable to the choices made by the recording engineers (at TRPTK, Brendon Heinst, Antal van Nie, and Hans Erblich; at 2L, Morten Lindberg).

There was little to choose when making the same comparison with B.ACH (TRPTK ttk0096). Featuring an instrumental group of seven musicians playing flutist Kersten McCall's arrangements in the smaller Waalse Kerk (the Walloon Church) in Amsterdam, the immediacy of the performers was clear in both Atmos (via the Arvus) and 5.1 24/352.8 FLAC (direct to DAC) versions (footnote 14). If there was any difference at all, it was that the projected space was marginally more generous in the former, while the higher-rez FLAC provided a feeling of more delicate detail.

The bottom line
There are really two. First, with the hardware finally catching up with the software, Dolby Atmos is going to be a major factor in music going forward. I think it may succeed, finally, in pushing multichannel reproduction into the mainstream. The 48kHz limitation may be an issue for some, but a horsepower race may drive that up if Atmos becomes a media standard.

Second, the Arvus H2-4D is the single piece of audio hardware that can deliver Atmos into a component audio system. Whether auditioned through its digital outputs (via my Okto DAC8 Pro) or its analog outputs (via its own, unspecified DAC hardware), the results were excellent. True, it was not made specifically for the home, and users may have to wrestle a bit with system integration, but their efforts will be rewarded. Adventurous audiophiles everywhere take note!

Footnote 9: The BPO's Digital Concert Hall provides Dolby Atmos 7.1.4 at 1024kbit/s via Dolby Digital Plus, the same technology used by Apple Music (although not necessarily at the same bit rate). It's lossy, sure, but to look at it another way, the 7.1.4 BPO feed contains about 30% more information than a two-channel CD-rez FLAC stream does. What's more, that extra information is far more sonically meaningful than some extra samples in a two-channel feed.—Jim Austin

Footnote 10: Actually, the H2-4D is not supposed to play Auro-encoded material, but it does. However, it displays it as DTS and the soundfield it generates seems quite different from the other formats. It is also different from what I hear with a real Auro-3D decoder on my other system.

Footnote 11: Dolby does include the Dolby Atmos Renderer in Mac and Win versions of its Dolby Atmos Mastering Suite. The suite is offered under an annual license.

Footnote 12: The app says it is free for 14 days and, afterward, costs $14.99 only for headphone use. Continued use of it for file output is free indefinitely. After install, click "Skip" to get to "Products" and select Setup for "Dolby Atmos for Home Theater."

Footnote 13: Free download from immersiveaudioalbum.com/product/iaa-sonic-brand.

Footnote 14: The H2-4D could play this file, but I could not get it to play it (or any PCM file) at more than 48kHz from my WinPC. TRPTK also offers files in DXD 5.1.4 WAV, which will be ideal once I figure out how to manage them.

COMPANY INFO
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COMMENTS
Kal Rubinson's picture
Submitted by Kal Rubinson on May 10, 2023 - 6:07am

One can certainly make that argument based on "the value equation." However, I take note that you maintain "two separate front ends: one is 2-channel, the other is theater" and, I am guessing it is because you do not think the HTP-1 is up to the task for your more critical 2-channel music enjoyment. My music is multichannel as well as stereo and this review was an effort to maximize performance beyond what we expect from entry and mid-level HT processors. That effort is continuing.

BTW, I am coming to prefer dB25 outputs that, in effect, allow me to more easily manage the XLR connections in practice and, as you do, I use a selector box with them.

David Harper's picture
Submitted by David Harper on May 10, 2023 - 8:46am

Hi Kal. When watching a movie with home theater surround does it ever bother you that the sound overwhelms the movie? I tried it for a while but for me the audio was so overbearing that it distracted from my enjoyment of the movie. I wound up going back to two-channel stereo.The one exception was with some new movies that are all cgi special effects, crashes and explosions the home theatre was cool since these movies don't actually have an intellegent plot anyway.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 10, 2023 - 10:47am

It generally does not but that may be due to program selection. We rarely watch any of the blockbusters and no "action" movies or "new movies that are all cgi special effects, crashes and explosions." As a result, our surround system's advantage over stereo is in intelligibility and ambiance.

Scintilla's picture
Submitted by Scintilla on May 10, 2023 - 11:07am

I do think that a higher-end front end for 2-channel is warranted and does obviously sound better in my case, in part because I am using HQPlayer to convolve filters built in acourate in contrast with the Dirac in the HTP-1. Further, I am running DSD128 out to a Holo May and Serene. This does in fact sound quite a bit better than the HTP-1 for 2-channel replay and once upon a time the systems were discrete. When I was forced to combine the sytems in a new loft, I went with split front-ends. However, over time I have come to believe that the perceptual impact of the Atmos or 5.1, 7.1 soundfield swamps any further improvements that would be wrought from an even higher-end discrete approach as you and Chris Connaker have pursued. Once you have a Dirac calibration and build filters for different purposes (such as dedicated music listening), allowing instant comparisons, I just can't imagine the real-world advantages of the discrete approach moving things that much forward. I think the brain gets inundated with so much information during multi-channel playback that it is impossible to tell the difference between any quality reduction compared to 2-channel playback. If one isn't fully satisfied with the performance of the unit for 2-channel, the answer is two front ends; if I didn't have the Holo first, I may (npi) not have even known what I was missing. To your last point, the back of the HTP-1 is a spaghetti-mess of monolith cables. Perhaps the db25s are a superior way to go... My next project is to buy Audiolense, build multichannel RC filters and drive the HTP-1 from HQPlayer with 24/192 PCM bypassing Dirac for my SACD rips. I think this may take things as far as the HTP-1 can go unless the Direct DSD of the AKM 4493 is made available through a firmware update. I think you would find the HTP-1 a groundbreaking product in sound quality comparable to discrete products with a much higher entry price. It is really a step up from mid-level AV gear.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 10, 2023 - 12:03pm

You raise an important issue.

Quote:

However, over time I have come to believe that the perceptual impact of the Atmos or 5.1, 7.1 soundfield swamps any further improvements that would be wrought from an even higher-end discrete approach as you and Chris Connaker have pursued. Once you have a Dirac calibration and build filters for different purposes (such as dedicated music listening), allowing instant comparisons, I just can't imagine the real-world advantages of the discrete approach moving things that much forward.

My only point of reference, so far, is the comparison between my CT system running via a Marantz AV8805 and my NYC system running discrete components, both with Atmos 5.1.4. There are many other differences between the systems (and rooms) but there is also an substantial difference in performance between the two. Another test will come soon when I review a very high end HT processor in NYC with the same amps and speakers I have now. I would not close the books on this issue just yet.

BluesDog's picture
Submitted by BluesDog on May 10, 2023 - 8:12am

Home Concert Venue Made Possible

A very outstanding, challenging but rewarding effort by Kalman Rubinson and John Atkinson. I DO agree we are at the beginnings of fully being able create a Home Concert Venue (HCV) at home.

Hopefully the hardware and software will continue to improve.

Thanks for your pioneering efforts and encouraging even die hard 2 channel audiophiles to consider new options to 2 channel sound.

Homer Theater's picture
Submitted by Homer Theater on May 10, 2023 - 4:23pm

I've messed with surround sound for music since the 1970s. I'm pretty sure I tried tried every format that has come along since the single passive rear channel and even analog processing of stereo into multi-channel. When immersive sound formats appeared, I assumed it would just be more disappointment. When decoding stereo music, Dolby Surround (what you get with Atmos to to make stereo through 7.1 sound immersive. It sounds horrible processing stereo music. DTS Neural:X sounds better than Dolby Surround, but is still not as good as stereo playback of stereo music. Then I tried Auromatic processing (now just part of Auro-3D decoding of shources with 7.1 or fewer channels) and FINALLY had my mind blown by upconversion to 12 channels that sounds better than stereo. In the years since the immersive formats have appeared, Dolby Surround is still terrible sounding--dry, dull, uninvolving, gray, and just generally unappealing. Neural:X hasn't changed either. And Auro-3D upconversion to 12 channels is still my first choice for listening to stereo music that's only available in stereo. I'll choose Auro-3D upconversion even over stereo. Dolby thought Auro-3D was such a threat to their existence, that they engineered a way to stop their TrueHD/Atmos sound tracks from being processed with Auro-3D processing (in movies). Auro-3D sued Dolby and won. Dolby has also tried to hire-away key Auro-3D employees--all in the name of trying to make Auro-3D go away. Too bad they didn't spend that time and effort trying to make Dolby Surround work better instead of attacking a competitor. For Auro-3D processing of stereo, I use 12 speakers... one directly above the front L&R channels and one directly above either the side-surrounds or rear-surrounds. The 12th channel is what Auro-3D calls the voice of god, a channel directly overhead. The other 4 immersive height channels are close to the 9-foot ceiling... the side- or rear-surround height speakers are on wall-mount brackets and are box speakers aimed at the main seat. I find down-firing in-ceiling speakers sound pretty bad compared to box speakers aimed at the audience. In-wall speakers sound less-bad than down-firing in-ceiling speakers, but still not as good as box speakers for immersive channels. Auro-3D upconversion of stereo to 12 channels FINALLY does stereo better than stereo. You might not think there would be much discrete sound in Auro-3D upconverted stereo, and that's sort of correct. When you hear music in a live performance venue, the sound mostly comes from in front of you and reflected sound comes from everywhere. That's pretty much what you get with Auro-3D upconversion. There are some sounds that are at least somewhat directional (other than left-right), but mostly you get a realistic amount of "height" immersion that makes the music seem less "flat" and more spherical with a front bias as you experience it at concerts. Auro-3D upconversion gives you fantastic sound from stereo sources, but also from 4.0, 4.1, 5.1, 6.1, and 7.1 original recordings. Auro-3D processing of Atmos or DTS:X soundtracks even sounds better because studios are not paying for a sound engineer to create Atmos or DTS:X movie soundtracks. Instead, they just use Dolby Surround on the original 5.1 or 7.1 soundtrack to get 11.1 channels and it sounds HORRIBLE with almost nothing appearing in the height channels for the whole length of the movie. You can get Auro-3D built-in to a fair amount of equipment... Denon, Marantz, Yamaha, and Arcam are installing Auro-3D in their products. Not necessarily every model of these brands will have Auro-3D. Generally it comes in mid-priced to high-priced models and NOT in lower-priced models. For those who need some sort of "magnitude of approval". Let's use a scale where a "10" is really excellent stereo music playback. Process that music with Dolby Surround, and you will be hard pressed to give anything higher than a "2" to sound quality compared to stereo. Switch to DTS Neural:X processing stereo music and you might feel like a "5" is an appropriate rating, with some possibly going as high as a "6". But process with Auro-3D and it's difficult to not want to give the music a "15" on that scale simply because the music is SO engaging. So musical, so enticing, and you don't even have to start with more than 2 channels. You don't even have to buy all your music again to enjoy this upconversion.

PS -- I've been a professional A/V equipment reviewer since 1995 and "into" stereo and surround sound since the early 1970s. I've even been published in Stereophile once, many moons ago. And I've known Kal Rubinson through online audio forums for years before either one of us were reviewing equipment professionally--and before the internet was live to the general public.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 10, 2023 - 6:30pm

Wow! I do agree with you that Auro-Matic up-conversion is preferable to the Dolby or dts alternatives but I have no real interest any of them. And when it comes which of the three "native" immersive formats I will buy, my choice will be dictated the program content, not the format.

MNSMike's picture
Submitted by MNSMike on May 10, 2023 - 7:50pm

The Dante output performance would be nice to know. Would be nice to know if a bitperfect output that follows the sample rate of the input, up to 24/192, is output via the Dante port. Like it does with the AES outs.

A simple way to test the Dante output would be to install the Dante virtual sound card on any Windows or Mac PC. And feed the audio to it. You would find out the sample rate capability anyways. To go further the Dante input from the unit could be fed from the computer to a USB DAC via ASIO. Where sine wave test tones could be analyzed with the AP from the DAC analog outputs. Then compared to the same sine waves played back direct from the computer hard drive to the USB DAC.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 11, 2023 - 6:42am

We are pursuing this now and will report on it.

MNSMike's picture
Submitted by MNSMike on May 11, 2023 - 9:59am

Thanks can’t wait to hear the results. There’s no owners manual to read. And the company won’t answer questions they feel might hurt sales if the public was to know. I have a feeling that if it does work with sample rates higher than 24/48, you must manually set the sample rate to a fixed setting. This means if you’re listening to a mix of music at different sample rates, you must go into the Dante controller on the computer, and manually change the sample rate the system is running at every time the music sample rate changes. Doesn’t make for a fluid listening experience. Not ideal for home audio users. Especially if the source is something like Amazon music on an Amazon fire cube. Where it’s capable of playing music up to 24/192 out of the HDMI port. If listening to music randomly, you can go from 24/192 to 16/24 to 24/96 to 24/48 with each track change.

And I’m afraid the same will be true for the upcoming Dante output only H1-D. Hopefully the actual capabilities of the unit will be shared with the public before they start accepting preorders for the beta version next month. As it stands now it’s pay first, and find out the limitations after you get it.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 11, 2023 - 10:26am

I am on it.

MNSMike's picture
Submitted by MNSMike on May 11, 2023 - 10:37am

Thanks. Consider getting an Amazon Fire-cube and an Amazon unlimited account if you want to listen to both a vast selection of Atmos, and 2 channel albums up to 24/192 out the HDMI port from a mass market black box device that just works. Alexa is far ahead of siri as well regarding voice commands. I have 2 Apple TV 4k’s and 1 Firecube, and I as much as I love my Apple TV’s, I’m not a fan of the 24/48 only sample rate limitation. Especially since their catalog has high resolution albums in it now. For music lovers the Firecube is the best option.

Kal Rubinson's picture
Submitted by Kal Rubinson on May 11, 2023 - 11:10am

Thanks, I will look into the Fire-Cube.

Scintilla's picture
Submitted by Scintilla on May 11, 2023 - 1:09pm

is for headphones, not discrete channels like Apple Music. I used a firecube for a few years and agree it has the best voice interface, but regularly, Apple beats Amazon in bitrates for content and Apple Music and Tidal are the only services offering real, discrete Atmos tracks. The Amazon content is designed for headphones, and therefore is rendering Atmos for two-channel virtual replay, not as a lossy DD stream with embedded top metadata like the other services. Amazon is very clear about this.

MNSMike's picture
Submitted by MNSMike on May 11, 2023 - 1:32pm

Not on the new Firecube gen 3. It works up to a full 24/192 bit perfect. I’ve verified it. Apple TV can only do 24/48 max. Regardless of how much high res content they have in their library. And it can do full TrueHD Atmos as well.

AC3 (Dolby Digital)/ EAC3 (Dolby Digital Plus) /Atmos(DDP+JOC)/AC4(Atmos)/Dolby TrueHD(Atmos)

Read all specs here:

https://developer.amazon.com/docs/fire-tv/device-specifications-fire-tv-cube.html

MNSMike's picture
Submitted by MNSMike on May 11, 2023 - 6:57pm

1 more thing to try. The Firecube 3rd gen supports full Dolby TrueHD Atmos. But none of the streaming services output full TrueHD Atmos. So I looked around for ways to take advantage of this feature. And I discovered 3 apps confirmed to work with Dolby TrueHD Atmos. Plex, Kodi and Jellyfin. With these 3 apps full 24/192 True HD Atmos can be sent out from the cube’s HDMI port with a very nice user interface, voice commands, and RF remote. And I believe they all have server apps that can run on a NAS, Windows or Mac to stream the content to them.

tnargs's picture
Submitted by tnargs on May 12, 2023 - 6:16am

The idea that 24/48 is audibly inferior to 24/192 is absurd. Sometimes I think that many audiophiles are becoming connoisseurs of ultrasonic tech and not of music at all.

MNSMike's picture
Submitted by MNSMike on May 12, 2023 - 9:59am

Depends what sample rate the track was originally recorded in, and the quality of the downsampling if it was higher. When these cheap boxes or TV’s downsample using mediocre algorithms, the degradation is very audible. I’d prefer to listen bitperfect at the native rate of the track.

BluesDog's picture
Submitted by BluesDog on May 11, 2023 - 6:46am

J Gordon Holt IS proud of what you have reviewed and how you reviewed it.

prerich45's picture
Submitted by prerich45 on May 11, 2023 - 8:12am

I actually went to the old Harman Kardon Citation 7.0 processor and hooked it up to my AV7706 through the 7.1 multi-in, as when I tried Auro3D up-mixing, it was bass heavy. I'm extremely impressed by the HK's performance (I've owned it before in the 90's). I have a SU-9N connected from my PC to the HK. I use convolution on mains through Jriver and I also have PEQ generated filters for the subs. What I was startled by was the flat measurement of the Infinity Overture 1 that I use as a center channel on it's stand. Pans are seamless - as the Overture 1 now stands about as high as the center section of my Infinity Prelude P-FR's. It's as I remembered hearing the Fosgate 3a system with the MC220 speakers - everything disappeared and sound just floated in space...around, in front of, and behind the speakers. The rears were subtle...not blaring just adding ambiance. I'm going to see if they have music that I listen to in Atmos, as I would like to hear a mix and compare it to my current up-mixing situation.

J-B-Lite's picture
Submitted by J-B-Lite on June 2, 2023 - 1:10pm

Thank you for this article, it is a valuable resource:
1) I've been looking for a testing file for Atmos playback--thanks for the Immersive Audio Album link. It's a nice demo and quick confirmation of channel levels. I was hoping for something like the AIX Blu-rays that have test tracks of 5.1 & 7.1 DD/DTS/LPCM pink noise for each channel and some combined. For instance, I use the track with combined front-right + Right-Surround (and ditto for left side) to hear the fantom image on the sides, then I tweak the distance settings of the surround on my Marantz A/V processor until that image sounds solid in the side locations between the front and surround channels.
2) I was pondering purchasing that Yellow Point disc, but found the album on Apple Music which is in both Atmos & Lossless simultaneously! It sounds fantastic, and I will eventually compare to my 2-channel HDTracks download.
3) which brings me to my next point, I listen to AppleTV 4K connected via HDMI and found the sound quality of "Lossless" and "Atmos" recordings not as satisfactory compared to two-channel CD rips (or HDTracks downloads) played back from my hard drive connected to my Oppo UDP-203 and connected to the Marantz AV7702mkII via HDMI. For instance, Lorde's Pure Heroine 24/48kHz downloaded from HDTracks in 2014 sounds more dynamic and detailed (with better 'microdynamics'?) than the Apple Music versions. I am wondering if some kind of volume normalization or something else is making it seem less dynamic to me. (I also tried increasing the HDMI input level on the Marantz for the AppleTV). Two-channel comparisons with other albums (like Michael Jackson's BAD & Dangerous albums) also sounded less 'powerful' or impactful via Apple Music (I'm not an audio reviewer).
4) Another nice feature of the AppleTV is that I can browse music using the Apple Music app on my iPhone, and have it play back & control the app on the AppleTV without using AirPlay. Airplay is limited to stereo, sounds inferior, and uses the phone's volume control. But when I am sending it correctly--connecting to my AppleTV's home theater configuration name, the volume is controlled thru my preamp and it is receiving Atmos playback if the albums are in that format. When I tried Apple's new Classical music app (when it first became available), I could not get it to output Atmos either from my phone or via using only that app on the AppleTV 4K.
I'm looking forward to your follow-up with the Amazon FireTV setup.

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