A&K SP1000 SS vs CU

Ultima Choice!

PROS: same price regardless of SS or CU, choice between two sound tonalities.

CONS: extra weight of CU, can’t roll back after fw update (SS/CU).

The product was loaned to me free of charge for the review purpose in exchange for my honest opinion.

Manufacturer website: Astell & Kern, Available from Audio46 and Amazon.

*** My full detailed review of A&ultima SP1000 DAP is now available HERE.


The first and the last A&K DAP I had a chance to test was AK120ii. Now, 3 years later, I still feature it in majority of my reviews as part of pair up testing with various IEMs and full-size headphones, and in comparisons to other DAPs in a similar class. So, when my readers ask me why I still use AK120ii (I get that question a lot), the answer is because that’s the only A&K DAP I have access to and because it’s still relevant. The meaning of relevance in today’s DAP market feels almost the same as in smartphone market, and coincidentally a lot of it has to do with catering to streaming, latest Android implementation, and the hardware to support it, which makes some DAPs obsolete in a short period of time after the release. A&K focus seems to be always on sound quality and user experience first, without worrying too much about general app support. That’s how they keep OS lean, fast, and optimized. And even so they provide access to Tidal (audiophile choice for streaming), we are not talking about open Android with a freedom to install other apps.

Recently, after getting the opportunity to test A&K latest flagship A&ultima SP1000, this DAP already became a permanent fixture in all my latest reviews. Soon, I will have a full detailed SP1000 write up, but in a meantime, I decided to whet everyone’s appetite with this mini-review focusing on SP1000 SS vs CU comparison, which I’m also planning to include in the full review. The subject of chassis/frame material has been a hot topic of discussions ever since A&K introduced different versions of their flagship DAPs. I can’t comment on the differences of AK240 or AK380 variations since I never tested it. And I have a feeling that not every SP1000 owner had a luxury to compare SS vs CU before deciding which one to buy. But I was fortunate enough to test and to compare both for a week, and then allowed to hang on to one as a review loaner to complete the full write up.

It wasn’t an easy decision to pick one, and I was flip-flopping until the last minute. I do hear a difference which I’m planning to describe, though I don’t have a definitive explanation why there is a difference in sound performance. Also, please keep in mind, the original comparison was done with SS and CU using firmware 1.06. The day I returned one unit back (CU), a new fw 1.07 was released and I only tested it with SS unit. To me, I felt like SS w/1.07 bridged a gap closer between SS and CU, though I don’t know how CU sounds with fw 1.07. My write up below will focus on comparison of SS w/1.06 to CU w/106, comparison of SS w/1.06 to SS w/1.07, and I will add WM1Z (fw 2.0) into the mix since I’m pretty sure everyone is curious about it. In all comparisons, I was using 64 Audio U18t, Sennheiser IE800s, and UM Mason V3, volume matched and playing only hi-res FLAC and DSD files.

I find it very important in this comparison to be clear about which firmware version I’m using, thus I will refer to SP1000 SS with fw 1.06 as SS1.06, SP1000 SS with fw 1.07 as SS1.07, and SP1000 CU with fw 1.06 as CU1.06.

Comparison – SP1000 SS (fw 1.06) vs CU (fw 1.06).

The first thing you notice when start listening to SS1.06 is the width of the soundstage. It’s the widest soundstage expansion I heard from any DAP to date. It has a good natural staging depth as well, more out of your head than intimate, but the sound is not exactly 3D holographic, rather more oval shaped, spreading from far left to far right. It almost feels like the width will go beyond the limit of natural expansion, yet it still has boundaries to keep it realistic rather than exaggerated. I’m not saying that it will make your IEMs or closed-back headphones sound more like open-back, beyond their tuning. But based on my experience of testing many different DAPs, SS1.06 pushes the performance of iems/headphones to their absolute limit.

In addition to SS1.06 open expanded sound, its tonality is brighter, a little colder, more analytical with a precision of micro-detail retrieval. It’s especially noticeable in mids and lower treble where you have excellent layering and separation of the sounds. For someone who wants to spend hours analyzing every single detail of your hi-res recording, you can really get lost nitpicking every sound while listening to SS1.06.

On a contrary, CU1.06 sound is more intimate, more musical, and a little more textured. It is warmer in tonality, smoother in retrieval of details, and just sounds a little more natural and less analytical. The soundstage depth is similar to SS1.06, but the width is a little narrower. Don’t get me wrong, it is still pretty wide, but in a relative comparison between CU1.06 and SS1.06 the SS soundstage is wider. Perhaps it’s the effect of the brighter tuning which adds more transparency and more airiness that creates a perception of a wider soundstage.

CU1.06 is still resolving, with an excellent retrieval of details, but it adds a little more analog texture to the sound and makes lower mids a little thicker with more body, and slightly less air between the layers. As a result, in a relative comparison, I feel SS1.06 has an edge over CU1.06 in layering and separation of the sounds, while CU has a more natural smoother musical tonality.

While CU1.06 sounds more natural and analog in comparison to colder and more analytical tonality of SS1.06, it’s all a matter of personal preference and will also depend on a pair up synergy with different IEMs/headphones and their corresponding sound sig.

As I always point out in my DAP reviews, when you are describing DAP sound, in reality you are actually describing a pair up synergy with iems/headphones you are listening too. Thus, I always choose a more balanced and less colored IEMs to analyze the sound of DAPs. When I tested and compared SS1.06 vs CU1.06, I found them to have more similarities in upper mids/treble tonality, while the bass and the lower mids is where I hear the bigger difference. SS has a more neutral bass with a little less sub-bass rumble and slightly less mid-bass impact, and a little leaner lower mids, giving the sound a more neutral tonality with more analytical precision. CU has a little fuller sound with deeper sub-bass rumble and more body in lower mids, giving the sound a warmer, smoother, and a more natural tonality. Upper mids and treble are close between SS and CU, but I do hear a little more crunch with SS, especially noticeable with some electric guitar tracks. The sound resolution is very similar, and both have a dynamic expansion with an excellent retrieval of details, though as I already mentioned above, layering/separation is better in SS version. With a leaner lower mids and noticeably wider soundstage, I hear SS having more air between the sound layers while CU is smoother and more natural, but at the same time a touch more congested in comparison to SS, especially when it comes to vocals.

As a side note, in both SS and CU versions I found a common difference between balanced 2.5mm and singled end 3.5mm ports where soundstage shrinks a little bit and the background is not as black from a single ended port.

Comparison – SP1000 SS (fw 1.07) vs SS (fw 1.06).

I wasn’t able to test CU with fw 1.07 since I returned it back right before the update. Thus, I can only analyze the difference in sound between fw 1.06 and fw 1.07 of SS unit. I know some people are skeptical about firmware changes affecting the sound quality, and manufacturers usually don’t comment on that either. But in practice, and not only with A&K but many other DAPs, I do find sound changes after firmware updates. Optimization of functionality and various background processes can all have some subtle indirect effect on the sound performance of the DAP. As I mentioned already, my intent is not to argue but rather to share what I hear.

In the original fw1.06, SS vs CU had a noticeable difference in soundstage expansion with SS being wider, and also a difference in tonality where SS was a little colder and more analytical, while CU was smoother and with fuller body (especially noticeable in lower mids). After fw1.07 update, SS1.07 soundstage width is now on par with CU1.06. Tonality of SS1.07 is also a little warmer, not exactly on the level of CU1.06, but somewhere between SS and CU with fw1.06. I actually think it sounds a little more natural now, giving SS1.07 a more organic tonality with a little more intimate soundstage expansion. I can’t comment on CU1.07 update because I don’t have it anymore, but in my personal opinion I wouldn’t like CU1.06 to be any warmer than it was already.

Page 2: Comparison to WM1Z and Conclusion.

11 thoughts on “A&K SP1000 SS vs CU

  1. Hello it was a shame I did not listen to the sp1000cu with the latest 1.07 firmware…i know what i am talking about….i had the 1Z too


    1. I will get that info from someone who recently updated his CU, and will let you know. I assume you have SP1000 CU now and thinking about fw1.07 update? 🙂


      1. Hello, the sound is even more natural but is not more warme, the voices are even bigger, the sound is more real, for exemple the battery drumstick is more thick with more “body” more presence…. is not easy to explain with words….


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