I don't write reviews but whenever I find something that impresses me deeply and I think that advertising it makes world a better place. This is the reason why all my previous (the all 2 of them) are giving 5 stars. This is going to be the third one. HQPlayer is a curious tool that, like May, changed the way I see things and listen to music.

Meta

So what is it? HQPlayer comes in 3 flavors: Desktop, Embedded and Pro. Desktop is a standalone player for PC. Pro is software for producers(?) to upsample files beforehand and distribute those pre-calculated. What I'm going to focus on here is Embedded.

HQPlayer Embedded is a software that you run on your computer and it integrates with Roon seamlessly. You can connect Roon to HQPlayer from Roon's settings and then use HQPlayer as your target. Roon will send music to HQPlayer which will then upsample it and send it forward to your DAC. Note that when using HQPlayer, you should not use Roon's DSP or volume control, but deliver music to HQPlayer bit perfect and let HQPlayer do all the processing or you are going to get lower SQ.

You can configure HQPlayer from your browser (localhost:8088, if it's running on the same computer where you are trying to access it). From there you can select filters modulators, EQ, crossfeed, target DAC etc. While the web UI is somewhat ascetic (and some people have given negative comments due to that), I personally would like the dev focus on creating more filters etc.

HQPlayer has a free demo and can be used for 30min (if I recall right) at a time and then it just needs to be restarted and one can play another 30min. Anyone can try it and test it properly themselves before the purchase.

The dev

And here we get to the developer. HQPlayer is developed by a Finnish guy Jussi, who is very active on internet forums answering questions. I've also got support from him and service has been A+. He is a busy guy, but tries to answer all the questions and is very helpful. HQPlayer seems to be a passion project of his and this may explain the price of HQPlayer a bit. Compared to cost of hifi components, I would say that it's very high value purchase.

Upsampling

I would split the upsampling operation into 2 sections:

1) Filters
2) Dither (PCM) / Modulator (DSD)

There are multiple variations of both available and both the filter and dither/modulator selection affect the sound, as does the frequency to which we are upsampling. I personally would describe the effects so that the frequency defines the size of the soundstage (the higher the frequency, the bigger the space and this scales somewhat linearly the higher we go, never saturating IMO) and filter defines how it's being used. Dither/Modulator is kind of a final touch, but it's role is still substantial. On dither side, the stronger the noise shaper, the more it gives certain depth to the sound and you can hear more things happening, but at the same time I think it loses some touch to the original timbre. On modulator side, the difference is more in accuracy/revealing and certain liveliness. I think with modulators there are more clear answers on what's better, but on PCM side (dither) it's more about taste of an individual and what works with one's equipment.

In these sections I try to list the available options and how I think they affect the sound.

Filters

There are multiple different "families" of filter (gauss, ext, xlr, sinc etc) and these all have their own "house sound". Then on top of that many of these filters are available as shorter ("MQA -like") and longer ("Chord -like") versions. Shorter versions seem to emphasize macro side of things, bringing big elements into the light. Shorter versions have less what's called "ringing" and they are somewhat smoother. Longer filters on the other hand have something that are called "faster rise times" and they kind of make the show bigger and bring out small details.

Also some of the filters are "apodizing". It means that they correct errors in the poor mastering process. Jussi (the dev) has commented that most redbook material (normal CDs basically) need apodization. One can configure HQPlayer so that 44.1 and 48khz material use different filter than "real hi-res". This way one can use apodizing filter for those and something else for others.

With Utopia I clearly preferred slower filters for some reason (favourite being poly-sinc-xtr-short-lp). I think it has something to do with smaller soundstage of Utopia. With longer filters there were too many things going on and that made it hard to focus into anything. Susvara on the other hand has a big soundstage and when used with longer filters, the stage becomes epic with a lot of information. While Utopia with shorter filters converted Utopia from "in my head" into "around me in the room", Susvara with longer filters is out of this world.

Something to note: especially those longer filters tend to be quite hard to compute. I could play most combinations with my i7 8700k, but especially when I went to DSD1024, my computer started struggling. However HQPlayer supports offloading filter calculation to CUDA, ie. GPU. I've bought second hand nVidia A4000 @ 600€ and that can basically calculate anything but the most demanding monsters: sinc-Mx and sinc-L @ DSD1024. Its power draw is also quite ok when playing music.

Dither (PCM) / Modulator (DSD)

Dither is responsible for cleaning up noise (that processing produces) from music and often moving it into the inaudible frequency range. Usually the more aggressive the dither, the better it sounds (to me). All the noise dithers and noice shapers on PCM side are quite light for computer and one can just pick the one one likes most.

On modulator side there are also multiple variations available. These modulators are responsible for converting PCM into DSD. Some of the modulators that many people consider "best" (EC) tend to be heaviest to compute and even the best CPUs in the market can't compute the Holy Grail of HQPlayer: DSD1024 with ASDMECv2 modulator. Modulator calculation also cannot be outsourced to GPU and the workload can't be split for multiple cores either. That's why one needs CPU with ultra strong single core performance.

This is where a self respecting audiophiles can put their wallets into a real test (again). Most demanding modulators need the CPU with fastest single core performance there is (i9-13900KS) and most demanding filters GPU with fast 64 bit floating point calculation (things like RTX A4000 or RTX 3080 and up). For a long time the "end game" from computing perspective is sinc-L filter + ASDMECv2 modulator @ DSD1024, but the situation has changed a bit with HQPlayer 5, which introduced even more demanding filters and modulators. However what people subjectively consider best differs and if you are lucky, you may not go all the way! Since the first appearance of this review I've aquired 13900k (with AIO water cooling) and with that I can run pretty much all the modulators on DSD1024, but the two most demanding few.

Subjective testing

I start this with a warning: YMMV!

I've read some people not hearing much difference when using HQPlayer, but I've often noticed that they have conducted their tests with setups with other bottlenecks. I think HQPlayer shouldn't be an item you buy in the beginning of your audiophile career. HQPlayer is most useful when connected to a TOTL system that can reveal what it produces and it's best partnered with a NOS (non-oversampling) DAC that can rip the benefits from the highest sampling rates. You may want to consult "Recommended hardware" -section here. I've tested it with Chord Hugo 2 and the result was a bit meh. However with my current setup, it has absolutely blown my mind (especially after I bought Susvara).

The test setup

Qobuz -> Roon -> HQPlayer Embedded -> HQPlayer NAA -> Holo May -> Holo Bliss -> Focal Utopia / Hifiman Susvara
(Intel i9-13900k + nVidia A4000 to power HQPlayer, Intel NUC for NAA)

NAA is Signalyst's free software that converts any small computer into HQPlayer compatible endpoint. This way you can for example keep the potentially noisy HQPlayer computer in a garage if you want.

General Impressions

First of all HQPlayer transforms Holo May into something absolutely incredible. The size of the soundstage grows a lot and different filters give me multiple different flavors for different genres and moods, still keeping the high sound quality. Longer filters kind of stretch the soundstage and reveal all the details in the music. Shorter filters focus on macro structures in the music, keeping things better together. The effect compared to pure NOS in May is by no means small, it's huge. Even between filters and modulators the difference is very clear (especially with Susvara, less with Utopia).

Filters

Personally I prefer some filters over other. I'll list some of my favourites here and will listen to those while writing.

Filter: closed-form-M16

This is closed form interpolation (not a filter in the similar sense) with 16 million taps. I'll start with this one as I think it keeps May's own nature intact. However as it fills in the missing values, it will be easier for May to reproduce the wave form and it results in a clearer sound.

This is absolutely beautiful filter with focals as I think it has probably the best timbre and thus the "feeling" can come through. It's very nice also for active listening when you want to focus on timbre.

The downside of this filter is that it's not apodizing and thus not good fit for poorly mastered material.

Filter: poly-sinc-gauss-xla

"gauss" family is the favourite of the dev himself and this is the longest of those. It's a bit smoother than closed-form-M16, but still very "human". This is the best all-rounder IMO. Many people prefer poly-sinc-gauss-long, which is the second longest. Gauss filters work very nicely with any kind of acoustic music.

Filter: poly-sinc-ext3

"ext" family is also very special, ext2 and ext3 being the most common ones being used (ext3 again the longer one). ext3 filters are (I think) a bit smoother than gauss filters. They are less full bodied than gauss, but there is some magic to their sound. Especially for electronic music, epic soundtracks etc. It's the most "entertaining" of them all.

Filter: sinc-L

"sinc" family is closest to Chord filters (according to Jussi) and the hardest to compute. The sound is very deep with amazing separation. It's analytical and beautiful. Really nice with jazz and classical, but also with electronics with interesting acoustic scenery.

Filter: sinc-Mx

Shorter than sinc-L. Soundstage is narrower, but this one is apodizing, which makes it a better all-rounder for mixed content.

Filter: poly-sinc-xtr-short-lp

Sound becomes much more intimate, but at the same time something feels very accurate. This is by far my favourite short filter and the one I use with Focal Utopia (however with Focal Utopia I also prefer PCM upsampling). This is beautiful filter if you want music to take you away in an intimate style. Music kind of glares.

Filter: sinc-short/medium/long (new with HQPlayer 5)

This is an amazing filter. It's non-apodizing and clearly competes with sinc-L. I think this one is more accurate and requires less memory, but is much harder to compute. I can only run the short version with DSD1024, but long version with PCM (1.536MHz). I think this is technically best filter and a no-brainer for PCM users as long as it being non-apodizing is not an issue. However I'm not sure if it's always clearly better than sinc-L. It's just a different representationn

Filter: sinc-MGa (new with HQPlayer 5)

This one is really interesting filter in many ways. Firstly: it's apodizing sinc filter. Secondly: it's somewhat easy to compute. Thirdly: it's constant time, which means that the number of tap increases linearly in the function of sample rate. It's basically a "competitor" of sinc-Mx in my books, but has an edge because of the easier computation. I do think that sinc-Mx sound clearly better to my ears, but I'm not sure if that would be the case in all the systems and for all ears. Also I think sinc-MGa is a bit brighter. It may be a bit too much of a good thing with Susvara.

Modulators

Everything will be tested with closed-form-M16 filter as I think that changes less in the sound and thus it may be easier to hear differences between modulators.

Modulator: AMSDM7 512fs+

My previous go-to modulator (before obtaining 13900k) that has been designed specifically for DSD512 and higher. This is still somewhat light to process (I can still run DSD1024), but among the lighter ones produces great sound IMO. It's very accurate and lively.

Modulator: DSD7 256fs+

Also really nice modulator that is light to process. It has less focus on the treble details than AMSDM7 512fs+ and it may kick a bit better (but it's hard to verify that). If I would be forced to say something about the lower registry, I would say that DSD7 256fs+ has a bit more kick, but AMSDM7 512fs+ bass is just a tad better articulated. However I could live with either of the two and I for example like to use t his modulator with closed-form-M16 if I want to listen to a bit more relaxed presentation of it. With modulators and filters, synergies do exist.

Modulator: AMSDM7EC 512fs+

This is quickly becoming one of the two of my favorite filters. It's also a bit lighter to process than ASDM7ECv2. It's a bit like ASDM7ECv2, but somehow more open. The nature is very similar with AMSDM7 512fs+, but it has a bit more kick and character. It doesn't have the last say in timing compared to ASDM7ECv2, but it's more spacious sound and also for example human voice sounds somehow more real to me.

Modulator: ASDMECv3 (v3 new with HQPlayer 5)

The feared and loved ASDMECv3. This was updated from v2 to v3 along with HQPlayer 5 and this was a major update. The new filter is not only better sounding, but also easier to compute. My 13900k can finally handle this at DSD512 with all the filters, though I can play DSD1024x44.1 with some filters. I like to pair this with gauss-xla as that filter supports cross-family oversampling (48x -> 44.1x) and then I can conver everything to DSD1024. This has the most hifi sound of them all. I'm right now listening to trumpet and and the transients are more accurate and correct than with "sloppier" AMSDM7EC 512fs+. Music also sounds more... music. Some kind of realism is lost a bit, but it's traded to more pure sound that is still analog. ASDM7ECv3 seems to be like Chord Dave in one way. I once read in head-fi someone saying about Dave: "it's nice to do the science experiment, but after some while, you will start asking yourself the question: do I like it?". I think it depends a lot on genres, synergies and personal tastes which modulator is the best in the end. ASDM7ECv3 definitely is a good candidate and I definitely see myself playing with it a lot.

Modulator: ASDM5ECv3 (v3 new with HQPlayer 5)

This is somewhat new endeavor for me. I started listening to it last week and noticed, that I like it. I feel that it kind of leaves something in music more untouched compared to ASDM7ECv3. I would describe it so that the sound is more "naked" and maybe fragile after ASDM5ECv3. If you have experience with Chord products, I would describe it so that ASDM5ECv3 is to ASDM7ECv3 what Mojo is to Hugo 2. Sometimes less is more. It kind of lets genres like metal and rock keep their human character better and doesn't try to make everything high culture. Also with some vocals it's easier to co-live those feelings with the artist.

Modulator: ASDM7EC-super (new with HQPlayer 5)

The new light and super modulators that came with HQP 5 are very interesting and I haven't yet understood them fully. They are first of all now the hardest filters to modulators and I can only run things @ DSD512. The first thing that strikes me when I switch between super and plain ASDM7EC is space. The soundstage isn't necessarily bigger, but it creates a sense of space. I think it works through slower decay, like there was some small reverb. Also the bass is a bit sloppier with these filters compared to plain ASDM7EC.

Modulator: ASDM7EC-super 512+ fs (new with HQPlayer 5)

This is very similar to normal super filter, but it's optimized better for DSD512 sample rates and higher. Sound wise I think the biggest difference is that the holographic separation gets better, but this kind of further emphasizes the sloppiness of super filters.

There are a lot of similarities to AMSDM7EC 512+ fs as well. I think AMSDM7EC 512+ fs has similar holographic effect, but is less sloppy.

On synergies between modulators and filters

I've noticed that some modulators and filters seem to synergize better. For example ASDMECv3 + sinc-L is a combination that digs very deep and reveals everything in the sound. However, it's not always the most realistic sound and is not the best fit for human voice for example. If I want to listen to something acoustical, I tend to switch to AMSDM7EC 512fs+ with poly-sinc-gauss-xla. gauss-xla has very natural transients, losing only slightly for closed-form-M16, but it creates a better sense of space. As AMSDM7EC 512fs+ feels a bit slower than ASDMECv3, it synergizes very well with gauss-xla, while sinc-L feels sometimes kind of too fast for the AMSDM7EC 512fs+ and sound can be kind of detached (or the reverb is kind of artificial). Also I think that gauss-xla kicks harder than sinc-L and to me it's sometimes a bit too much with ASDMECv3, which is also a bit more aggressive modulator than AMSDM7EC 512fs+. In near future I will probably investigate further how gauss-xla pairs with the new super filters.

Ending notes

The domain of HQPlayer is just huge and I could just keep going on for days as the rabbit hole would probably never end (or maybe when we would start talking about overclocking CPUs with nitrogen and stuff like that). I think HQPlayer has earned this review. I've been like a child in a candy store with all the nice filters, especially since I got A4000 GPU. HQPlayer provides many beautiful variations to the system and IMO is an absolute no-brainer to try for whoever has good enough system that is able to reveal these hidden treasures.

Bravo Jussi and hurry up Intel!

This review is going to be short and to the point as I just want to get back to listening. I don't think there is much to say about Bliss other than "this is it". I got the same feeling already from SparkoS Aries to be honest, but its lack of enough volume steps kept me looking for an alternative. I feel that Bliss finalizes my search for a perfect solid state amp by adding enough steps in volume control and as a nice bonus adds this extra character in sound that I didn't ask for but that I very much welcome.

Features

I think Bliss has all the features that I would wish from my headphone amplifier. It has two balanced and one SE inputs; 6.3mm, 4.4mm, XLR outputs; it has remote; it has stepped relay volume control ranging from -72db to +12db; it has preamplifier with SE and balanced outputs; it has mute. I'm happy. The only thing I could come up with was that I think it would be nice if it remembered volumes of different outputs. Now they are all the same. However as I think I will be using just XLR 99% of the time, to me it's not critical, but it may be something that an active user of preamp could wish for.

Setup used

Qobuz -> Roon -> HQPlayer -(USB)> Holo May -(BAL)-> Holo Bliss -(BAL)-> Utopia/Susvara

My favourite HQPlayer setting for Susvara:

poly-sinc-ext2 | DSD7 256+fs | DSD1024
Jan Meier 650 / 13

This creates a massive and realistic soundstage and also tames down the upper region just a tad. Pure perfection.

Power and Susvara

My guess is that many of the readers of this review will be looking for an answer to question "Will it drive Susvara?", so I'll start with that.

Yes it does, Bliss is powerful. You can breathe again. Also, actually it shouldn't be a surprise as Susvara was used as a target when designing Bliss! As a reference: when I'm using Holo May in DSD mode (2.9Vrms from balanced) and also attenuate that signal -3db in HQPlayer, I'm normally listening somewhere -30db and -25db if I want to go crazy. I'm listening at -31db as I'm writing this review. -20db starts to feel quite uncomfortable and I very rarely go above -25db. This means that I have basically still 30db+ in tap (+12db max level) that I'm never using. If I didn't use HQPlayer and I used PCM from May (5.8Vrms), we could add 9db into these numbers. Yes, with Susvara.

I know that I have sensitive hearing and I've read some wild comments that some people have listened Susvara @ -5db, but I would be very worried about my hearing if I did that. However even if I did, I would still have 17db in tap which is actually quite a lot in terms of power. I'm very comfortably saying that Bliss has enough power for Susvara.

In terms of sound, Susvara sounds amazing from Bliss. End of story. It's authoritative, accurate and natural, never going harsh. The holographic and liquid nature of Bliss is amazing with Susvara and together they paint a soundstage that I have never heard before (especially when married with Holo May and HQPlayer).

Sound character

I would describe the sound of Bliss as very transparent, holographic and liquid (liquidity especially after 1h warmup). By holographic I mean that the placement within soundstage is good and I can basically hear shapes, not only direction of sound. Liquidity is a bit harder to explain. I would just describe it as lack of harshness, but it's different from smoothness. I think Topping A90 was smooth, but this smoothness comes with the cost of some added veil. I'd describe the difference so that smooth is like diving in foam and liquidity is like diving in water. In foam everything is smooth, but you can't clearly feel the borders of things. In water you can still feel the border of you and your surrounding clearly, but it's still always pleasing and "goes your way". This is in contrast to being against brushed metal for example. I think Hugo 2 was a bit like that. It was kind of unforgiving, non-negotiating and without sense of humor. Bliss is never dry or boring. It's Class-A.

VS SparkoS Aries

Purely sound quality wise Bliss is also the best headphone amplifier I have heard. Unfortunately I didn't have SparkoS Aries anymore when I got Bliss but I feel that they are similar in terms of detail retrieval and refinement. However this liquidity of Bliss makes the sound signature preferable (to me). Also the sound is more holographic which feels very classy and something that is about to spoil me. Aries and Bliss have both big soundstages, but placing within the stage is better with Bliss.

VS Singxer SA-1

I did have Singxer SA-1 when I got Bliss as I had bought it from classifieds as a temporary amp and I also wanted to give it a shot before ordering Bliss (it was Class-A, measured well and had good reviews). However SA-1 felt like a downgrade after Aries and when I got Bliss and I did A/B between SA-1 and Bliss, SA-1 felt toyish in comparison and the sound kind of lost it's grip of me. I did that A/B testing with Focal Utopia.

However I would still very warmly recommend Singxer SA-1 as I think it's amazing value in it's price point. I would personally upgrade my DAC first and only after that upgrade my amp. Jump from Qutest to May was much bigger change in my system than jump from SA-1 to Bliss. Not to mention jump from Aries to Bliss. Please also do note that I only bought Susvara after Bliss, so I don't know how much Susvara would lack with SA-1.

Summary

I think Bliss deserves a spot in solid state hall of fame. It has has both an amazing sound quality and an amazing character. It can run Susvara well, has all the necessary features and doesn't have any obvious flaws. For many it may be the end of the road in the search for a perfect solid state headphone amp.

It was for me.

History

This is my first review I'm going to write. It's been 10 years since I bought my HD800 and DNA Sonett. After that I've owned many combinations of headphones and amps and more lately, dacs.

Many people that are new in the space probably at some point hear the old saying : "If you want to change the way your system sounds, just change the headphones. They contribute most to how things sound.". I'm not going to say that this is totally wrong, but based on what I've learned during my journey, I would like to adjust that way of thinking a bit.

Today I see the chain as follows: the headphones as the magnifying glass, amps as a window (that can be magnifying, but glass anyway) and DAC as a TV. Recordings are movie files that we watch from the TV through these two glasses. Good headphones and amps reveal the picture in the TV. This is why some people say that some headphones "scale" with better system. I think those headphones always let the light go through the same way, but sometimes there just is nothing to see. If the window (amp) is blurry, TV is not 4K, but 720p or the movie file itself is poor quality (720p or just recorded with poor equipment - "home made"), it matters less how transparent the last magnifying glass (headphones) in the chain is.

Why this tends to take so long to realize? Because one needs to 1) have trained ears that are used to hear differences between systems AND 2) at some point end up listening a system in which all of these elements in the chain are high enough quality.

You need to listen
1) well recorded music
2) in FLAC/DSD (ie. lossless)
3) from a software that puts this through bit perfect (do not underestimate this, Windows absolutely ruins the music so that no high end system sounds better than mediocre)
4) from a TOTL DAC
5) through a TOTL headphone amp
6) through TOTL headphones
before you have a reference point for what true 4K sounds like.

Now, I will give you a story. I listened to Focal Utopia in a shop when it came out years ago. I had my HD800 with me in a shop and after doing some comparison between the two, I was "meh" and my conclusion was that HD800 was better or at same level, just different. However, a year ago the destiny got me together with Chord Qutest as it made my toe tapping (something that my Sony TA-ZH1ES didn't do). After I had familiarized myself with Chord sound, I started getting interested in TT2 and Dave as I felt like I was still missing something. I wanted to keep the Chord sound, but I wanted different soundstage and I felt like amps couldn't quite do the thing for me. Again, I went into a shop, tried Dave with HD800S and then compared that to Hugo 2. The difference was definitely there, but it was still more of a side wise move. Then I did something: I plugged Focal Utopia to those. That changed everything. While Utopia sounded good from Hugo 2, it was an absolute moonshot when plugged into the Dave. It wasn't colored, pleasant, even fun. It was just that nothing annoyed me and the staging was... right. That was a weird moment of realization.

I realized that there are dacs and there are DACs. I also realized that one needs to use TOTL DAC to hear the potential of TOTL headphones and vice versa. The rest is history. I searched around, read everything about dacs, noticed that many of the TOTL dacs are R2R dacs, Holo May was one, measured perfectly and had raving reviews (especially when used with HQPlayer) stating that it's better than Dave. Someone had May KTE in classifieds and my wallet was crying blood.

The Copper Teacher

So, The May.

The setup I'm using it with is:
Qobuz -> Roon -> HQPlayer -> Holo May -> SparkoS Aries -> Focal Utopia (and MDR-Z1R when I want to listen to soundtracks or when I need closed back)

HQPlayer settings I've mainly used:
DSD: -3dBSF | poly-sinc-ext2 | ASDM7ECv2 | 12288000
PCM: -10dBSF | poly-sinc-ext2 | LNS15 | 1536000
Settings: DAC bits 20 (dev's recommendation for May), 48k DSD enabled, Auto rate family enabled
Post processing: Jan Meier cross-feed / 650 / 9.5 (the same as Chord Hugo 2 on lowest setting)

For reference, my other current and past items:
Current: Softears Cerberus | Chord Anni/Hugo 2+2go | SPL Phonitor e
Past: Chord Qutest | Denon AH-D1000 | DNA Sonett | DragonFly Red | Feliks Audio Euforia AE | Graham Slee ULDE | Hifiman HE-400i/HE6se v2 | iFi iDSD LE | Sennheiser HD800/IE80 | Sony NW-WM1Z/TA-ZH1ES | Topping D30/A90

This has shown me a new reality. I feel like I have time before May and time after May. I can recognize that the music is the same, but everything is just so different now. Unfortunately I can't do side by side comparison to Dave, but right now I feel like that is a more side ways move. I could probably live with either one and be happy. I just think that I'm... happier with May. Why? Because while the Dave gave me the most non-annoying sound I've heard (though it WAS kind of intoxicating), May just... It has this grab. I don't need to go anywhere, I just want to be where I am when I listen to it. I just want to stay there. I constantly get these feelings that things are so right and it keeps delivering.

To me the question isn't about which one is better: May, Dave, MSB... The question is these vs. the world. The beauty of May to me is that while it's expensive, it's still a somewhat achievable port to this different realm (for the reference, I think my DAC is currently more expensive than my car).

But what do these do differently exactly?

I think after Chord Qutest -level, we are not talking about detail retrieval anymore or if the frequency response curve is flat. All of those DACs have that. The biggest differences are IMO in three things: staging, effortlessness and realism.

Staging

I think this is the reason I wanted to switch from Qutest to the next level. For a very long time I tried to get better staging with amplifiers and headphones, but hearing Utopia with Dave made me realize that the problem was that the staging wasn't good in the first place. Remember the TV comparison earlier? Now think that the staging of the DAC is the size of the TV. If the TV is 32", it's really hard to make the view impress you by trying to save the situation with magnifying glasses. What May and Dave both do (compared to lower level dacs) is that the TV is 100" in the first place and the rest of the chain just need not to ruin it by squeezing it together. I much, much prefer using May (big stage dac) with Focal Utopia ("small stage" headphones) vs Qutest (small stage DAC) with HD800S ("big stage" headphones), if that makes sense. The end result is much more natural, pleasing and effortless. Also now the stage can be at the same time intimate and huge (when the music calls for it).

Effortlessness

May is effortless in how it presents everything (a term I've heard many times and it feels very natural to use it in the case of May). However this I think I got already to some extent from Chord TT2, though not exactly the same level. I think this is somehow related to the staging. It's like, when there is space between the instruments not only in x,y axis, but also in the z-axis as well, it's more natural for brain to distinguish and follow (=process) different sounds and one doesn't feel that one needs to extract all the information from a small and dense ball of sounds in a hurry. It may be that this sense of effortlessness comes from something else as well, but this is how I would put it.

Realism

I think this is the hardest to explain of the three. Also I think this is where May does some very special magic and is one of the secret sauces behind May's success. I think this is what gives May its "grab" and it kind of works subconsciously. One doesn't need to listen to May for very long before one notices this feeling that something is very right. For me this didn't do the immediate classical "you start smiling" -trick but instead something just talked to me, quietly, and reached very deep. This became even more apparent when I tried to change something or leave the listening spot. I suddenly had this very strong urge not to. It started to feel like I would leave the presence of a friend.

NOS

Then, I think that as a reviewer it's my responsibility to mention a word or two about the NOS side of things. You will find a lot of information while googling around and watching other reviews of May, but I'll mention something very briefly. May is meant to be used in NOS (non oversampling) mode. Most of the DACs do some internal oversampling before they actually convert the bits into sound and also May does have this capability, but it's not actually its strength. Its strength is that its implementation of NOS is not only true NOS, but also a very good one. While it sounds great just in NOS mode as well (with good recordings), the benefit that NOS brings is that it separates the DAC itself and the oversampling filters it uses. One can use MScaler or software like HQPlayer that have state-of-the-art filters that are probably better implemented than the ones in DACs. Your computer most probably also has more computing power to use higher quality filters. With May you also don't pay (much) for the filters of the DAC that you may not want to use anyway. I've found that the combination of HQPlayer and May is sublime and provides a lot of flexibility to the sound. One can fine tune the sound with different filters and noise shapers in HQPlayer to match the taste (and mood) of the listener. It's also a great learning experience to dive into this world. I also want to mention that my review of May is kind of strongly coupled with an assumption that one uses HQPlayer or some other proper oversampling software/method. Personally if it was a requirement for me that the DAC must be "plug and play", I would probably watch elsewhere, like Dave. While to my ears May sounds really good in NOS mode with good recordings, it also does sound sometimes harsh with bad recordings. Good oversampling simply makes it versatile to be used with anything and more often than not, makes things sound better.

The wish list

For May 2.0 the wish list of things isn't long, but there are two things.

First: I'm using it with sensitive headphones and I've found 2.9V output to be a bit hot sometimes. With Utopia even the lowest -52db setting of SparkoS Aries is already quite loud and I unfortunately can't use my Softears Cerberus with this setup without some external attenuation. Luckily with HQPlayer the problem is much smaller as I can adjust this with headroom and HQPlayer does this quite well. However to me, especially at this price point, digital attenuation<lower gain. Also with software based attenuation I'm a bit afraid that some system ping goes through +10/13db louder than music (or I simply forget to turn down the dial after switching away from HQPlayer). That would be very unfortunate if I was already listening at very loud levels.

Second: The remote has volume buttons while May doesn't have volume control. This is a very small thing for me, but still. It feels strange.

Ending words

I think I could keep talking for days, but I'll just stop here as I feel like I've mentioned and explained the big thing I wanted to talk about. Everything else is nice and right, like timbre, detail retrieval, black background, good USB implementation etc. However I kind of had expected those to be good already when I came from Qutest. To me the one thing (which also is a big thing that changes basically everything in the way I see the system) where these TOTL DACs differ from other dacs most, is how they present the soundstage. Then what's special to May is that 1) it's a R2R dac and 2) it's a NOS dac, 3) it basically measures perfectly and 4) it has this magical grab. If you want to up your DAC to state-of-the-art TOTL, are not exactly swimming in cash and NOS rings right bells for you, you owe yourself to at least demo May. It's an amazing unit that will not be the bottleneck of your system, 100%. If you just want a plug-and-play TOTL DAC that comes with good filters already baked in, you may want to look somewhere else. If you are are going to say that Topping E30 measures the same, buy Topping E30 and be happy. If you are swimming in cash, do whatever you like.