SINGXER SA-1 V2 HiFi Headphone Amplifier – Boundless Smooth Silk Music Flow
Singxer SA-1 V2 is a $599 USD Headphone Amplifier / Desktop Stereo Preamplifier with a high-end internal design, upper midrange pricing, and a beautiful design that makes most of the competition pale in comparison. Thanks to its Class A architecture and completely analog design, SA-1 V2 is the focus of our review today, and we will take an in-depth look at the usage and sound, but also compare it with other amplifiers, including iBasso PB5 Osprey (1499 USD), Aune S17 PRO (699 USD), Feliks Audio Echo 2 (799 USD), and Rebel Amp (599 USD).
Introduction
It has been a long while since we reviewed out first product from Singxer, and our format as well as our approach has changed multiple times since then, Audiophile-Heaven grew to now have over hundreds of thousands of viewers each month, yet my original review of the SDA-2 still stands, it was a super interesting Headphone Amplifier, and can still be considered relevant. Just like seeing an old friend as you both grew while apart, I like seeing Singxer being supported and sold through countless channels, in Europe being supported by most large HiFi shops, Amazon, Aliexpress and everything in between. Singxer made a name for themselves for their excellent customer support and product q quality and although the product we are reviewing today is far from being their flagship, the first version of the SA-1 has been one of the most popular headphone amplifiers of their time, so V2 should be improved in every way possible. As an Amazon Influencer, I earn from qualifying purchases, and using the purchase links in my reviews helps me maintain this website and Youtube Channel. Huge thanks to Singxer for providing us with the sample for this review.
PROs – Extreme levels of driving power, huge headroom, relaxed and laid-back sound that forgives all mistakes. Solid build quality, and it never really gets too warm or hot, despite running in full Class-A. The background noise level is almost zero, while the maximum driving power is all usable, up to maximum listenable volumes, with perfect control. Fully balanced design, with proper XLR input, XLR Preamplifier output, and balanced headphone output.
Cons – Gain switches on the bottom sure are not easy to reach. Extremely smooth and relaxed sound is an acquired taste and not a generalist sound.
Product Link
Amazon – https://amzn.to/4dvKGEf
Aliexpress – https://s.click.aliexpress.com/e/_De93Dzf
Build Quality/Aesthetics
Physically, Singxer SA 1 V2 is a high-end modern-looking amplifier, with both XLR inputs and XLR Preamplifier outputs, RCA inputs, RCA Preamplifier outputs, and a combination of XLR, and 4.4mm headphone outputs, and a 6.35mm single ended headphone output. Compared to the 1st version, SA-1 V2 has a higher driving power, with more thrust and impact, having an optimized circuit, and a higher output power for low-impedance and low-SPL Headphones.
The circuit used by Singxer is fully analogic, with no digital parts. The company implemented ROHM input transistors, to ensure a low noise, and the output stage uses a multi-stage current amplification, similar to those found in stereo power amplifiers. Each channel incorporates 2 pairs of ON Semiconductor 4A Transistors, to ensure a low internal resistance and high output power. Something quite unique to SA-1 V2, we have a bipolar switch for selecting the output power, allowing you to drive either low impedance or high impedance headphones. There is another switch to select between the XLR and the RCA input, and another one that turns the SA-1 V2 Off, to Pre Function or Headphone Amplifier function.
The whole unit runs in full Class A, and the THD+N is -120dB for high gain, and -96dB for the low-gain. The sNR of the unit is likely the highest I have ever seen on a unit, even for technical measurements, 147dB. The driving power level, as quoted by the company is ultra-high, so I will copy it over for better readability.
Balanced output: 10000mW @ 16Ω
Balanced output: 5500mW @ 32Ω
Balanced output: 3100mW @68Ω
Balanced output: 2000mW @ 120Ω
Balanced output: 380mW @ 600Ω
Unbalanced output: 500mW @ 16Ω
Unbalanced output: 1375mW @ 32Ω
Unbalanced output: 775mW @68Ω
Unbalanced output: 500mW @ 120Ω
Unbalanced output: 95mW @ 600Ω
The output impedance changes heavily if you engage the low and high impedance switch, with the output impedance when set to low being 1.4 OHMs for the balanced output, and 0.7 OHMs for the Single Ended headphone output. Although this is not evident right from the start, the high impedance setting turns things high, with the output impedance on high-z being 11.4 OHMs for the balanced output, and 10.7 OHMs for the single ended output. I cannot hear the background noise with the low-Z setting even with IEMS, despite the number being theoretically high.
With a weight of 1.8 kG, SA-1 V 2 is stable on my desk, and the package includes a power cable, with the unit working between 100Hz and 240Hz, perfect for both Asia, USA and Europe. Subjectively, as an amplifier it does not introduce any kind of sonic delay, and surprisingly, the unit does not grow hot during usage, and it is barely warm regardless of the volume I am running it at.
Sound Quality
Pairings – At the DAC end of the AMP, I had a few stars powering it, including Musician Pegasus II R2R, SMSL DO200 PRO, Burson PlayMate 2, HIFIMAN Serenade, HIFIMAN EF400, Dethonray listening M1, Aune S9c PRO and FiiO K9 PRO ESS. For the headphones and IEMs I’ve been driving out of the Singxer SA-1 V2, the most important ones are HIFIMAN HE1000SE, HIFIMAN Audivina, BQEYZ Winter, Soundz Flame, Audeze MM-100, Crosszone CZ-10 Enhanced, Crosszone CZ-8a Enhanced, Sweear HE-Live5, Soundz Avant, and Campfire Bonneville. With headphones, regardless of the SPL and impedance, SA-1 V2 has plenty of driving power and a large headroom, and I challenge you to ever try to reach the maximum volume, being one of the few headphone amplifiers in the price range that has so much power on tap. The Low-Z / High-Z impedance switch will change how the AMP drives the headphones, and on high-z it works better with the likes of Sivga SV023 and Sennheiser Hd660S2. Low-Z or low impedance works well for most other headphones.
With IEMs, I can hear zero background noise both with high gain and low gain. At high gain, I do not have enough volume control with IEMs, so the switches on the bottom set to low gain allow me for far more volume control, which is very helpful. There is minor channel imbalance up to 9 – 10 o’clock, so I fully recommend going with low gain for IEMs. The noise floor does not increase with volume, or gain, so you can be free of worries, even Campfire Bonneville, and Campfire Moon Rover show zero background noise, so the same will be true for every IEM out there, including Soundz Avand and Sweear He-Live5.
Signature – While the original SDA-2 DAC/AMP sounded fairly capable, it is now becoming more clear why Singxer climbed so quickly in popularity and how it is now one of the most popular headphone amplifier / DAC producers, having the smoothest, deepest and most relaxed tunings I ever heard in their SA-1 V2. Itr feels like I’m listening to a pure silk flow of boundless music notes, with a full but natural and distortion-free bass, fluid midrange, and smooth, relaxed, laid back treble. The whole sound is as detailed as it can be, but focused on being forgiving, lean and pleasing, with no hard edges, no fatiguing elements and what I consider to be exceptional musicality and smoothness. If you ever wanted to hear how pure nectar, sweetness and warmth sounds like, SA-1 v2 will be happy to deliver on all ends a tuning that is as lush as it is rich and pleasing.
Bass – Starting with the low-end, SA-1 V2 delivers pure smoothness, but it is not the amount but the smoothness and fullness, warmth and extension, control that truly impresses every single listener on each listen. Even with the greedy hungry headphones like He1000SE, the bass reaches new levels of depth and impact, the sound having a 0% audible THD even if you close on the maximum listenable volume. Bass has most of the energy focused between 20 Hz and 50 Hz, the sub bass low-end where everyone feels like qualitative sonics play, and the tuning every single song into a veritable earthquake inside of my head. The interesting aspect here is that even with headphones that don’t normally have a strong bass, you can get a voracious bass as you can pump the volume a great deal and distortion never kicks in.
Midrange – With a smooth, full and dynamic midrange, SA-1 V2 paints the music in multiple layers, usually sticking to a frontal forward layer that plays where most amplifiers paint the middle layer, and a background layer that is pushed far in the background. This tuning creates a huge space for music to play in, and a much better instrument separation, along with a stronger imaging than most amplifiers have. The voicing emphasizes male voices and deep female voices slightly more than brighter female voices, and the tuning is serious, deep and powerful more than it is happy and light. A grave and deep sound is desirable with Jazz, Classical, Metal and Rock music, Downtempo and Rap.
Treble – Top top things off, the treble is the smoothest, silkiest and most relaxed sound you can dream of. Listening to SA-1 V2 puts you in a dream-like state where you let your imagination run free, and focus downwards to your feelings and emotions, unhindered by any kind of sharpness or brilliance that would bring you back to reality. If this kind of forgiving experience is your cup of tea, SA-1 V2 delivers it, while keeping details and technical resolution the highest I have ever experienced.
Volume Control – Although at 599 USD I typically expect some kind of variation with volume, SA-1 V2 stays surprisingly consistent across volume levels, having a smooth, relaxed and laid-back sound from the quietest all the way to the loudest volumes. One thing that is truly characteristic of SA-1 V2 is how well it controls distortion, and the full Class A Headphone amplifier, paired with the high headroom and driving power means you can really pump the volume into the 110 dB – 120 dB range without running into distortion.
Dynamics / PRaT / Textures – Regardless of the volume, SA-1 V2 has a really slow and relaxed impulse response, creating a smooth texture, warm and laid-back sound, it is silky and fatigue-free, with a strong sense of forgiveness. You will basically not hear sibilance, harshness, grain, although you will get a sense of warmth, depth and texture from music.
Soundstage – Sinxger manages to generally create a wide and spacious staging with their SA-1 V2, thanks to the way it seems to push most instruments farther away from the listener than most amplifiers, creating both width and depth. Music is always fairly distant and wide, with a large space between instruments. The tuning exposes and reveals details well without breaking the relaxed and silky smooth tonality.
Comparisons
Singxer SA-1 V2 vs Feliks Audio Echo 2 (599 USD vs 799 USD)
Build – Echo 2 is an OTL Amplifier, so you’re likely to drive mainly High-Z headphones, and it also can work as a Preamplifier, but has only RCA Single ended inputs and outputs. This inherently means that Echo 2 is more sensitive to noise inherited from the DAC, and you will hear it when the DAC is not well isolated, while SA-1 V2 has XLR inputs which help it stay cleaner in most situations. Singxer includes multiple balanced outputs for headphones too in their SA-1 V2, with far more driving power, and control, with multiple gain levels, so it handles IEMs better too.
Sound – When both are driving the same pair of headphones that Echo 2 can handle well, like Sennheiser Hd 660S2, or Sivga SV-023, Echo 2 sounds more juicy in the midrange, more colorful and more contrasty, while SA-1 V2 sounds much smoother, leaner and more relaxed, while Echo 2 is brighter and has more bite / energy in the upper midrange. This means that you can expect a sweet and uplifting sound from Echo 2, and a more serious, more refined sound from SA-1 V2, with more bass extension, punch and depth. Those tunings are very similar when using either as a Preamplifier, although the difference in the bass is less evident if both are used as Preamplifiers.
Singxer SA-1 V2 vs Rebel Amp (599 USD vs 599 USD)
Build – Rebel AMP is green, is powerful, and sadly it is gone too. Right now I cannot find any more places to purchase it, and it appears as sold out on the Rebel website, so I assume that our review of it was successful, and the company currently cannot keep up with the demand, and every piece built is immediately sold. Rebel AMP has only a single ended headphone output, while SA-1 V2 has both two balanced headphone outputs, and a single ended output too. Rebel AMP supports only RCA inputs and one RCA Pre output, while SA-1 V2 supports both RCA and XLR line in and preamplifier output, with multiple gain levels, although Rebel AMP also has three gain levels.
Sound – Sonically, the two are fairly similar, Rebel AMP also sounds fairly warm and smooth, but SA-1 V2 is much smoother, leaner and more relaxed, more forgiving, and has a more neutral bass, while Rebel AMP sounds warmer, and brings in more bass, more volume and less space, sounding more intimate. SA-1 V2 sounds really extensive in the staging, projecting music far away, wide and well defined. As you cannot order Rebel AMP at the moment, SA-1 V2 is a good replacement option with a more versatile design, being both fully balanced and fully Class A.
Singxer SA-1 V2 vs Aune S17 PRO (599 USD vs 699 USD)
Build – Both AMPs have the same level of inputs and outputs, but S17 PRO has a really nice display, which shows you its temperature, it has two modes, one at 50mA and one at 100mA, and it also has both XLR inputs and RCA inputs, the two Amplifiers being comparable. S17 PRO is known to grow hot easily, and I have received comments from fans who purchased both telling me that their S17 PRO cannot keep running in full power mode, as it easily reaches the temperature cap. I have not had this happen with SA-1 V2, and while in my experience S17 PRO does get quite hot, SA-1 V2 is literally cool to the touch while I am using it at all gain levels, or volumes.
Sound – Sonically, the two amplifiers are similar in refinement and smoothness, but S17 PRO sounds quite a bit warmer, adds more bass and low-end volume to the sound, makes the music more intimate, while SA-1 V2 projects music far away from the listener, creates a higher degree of separation and more layering. The technical resolution is similar, although S17 PRO has a bit more treble too, so it can show textures and certain micro details more than SA1 V2, which always stays more relaxed and more forgiving, with less treble and more bass.
Singxer SA-1 V2 vs iBasso PB5 Osprey (599 USD vs 1499 USD)
Build – iBasso PB5 relies on NuTubes to create the sound, it has a portable, compact design, while SA-1 V2 is smaller than HIFIMAN Prelude, but it is still a desktop amplifier that needs a full power outlet with its own internal power supply. PB5 has only one 4.4mm input, and the best output is a 4.4mm balanced output, with an additional 3.5mm single ended output. Both are quiet for driving IEMS, and have a huge headroom for driving hard and power-greedy headphones, but at the same time PB5 has theoretically a lower power, although I have not reached the headroom limit of either yet. Both AMPs stay cool, but PB5 has a battery and can work for quite a while without needing power on the tap.
Sound – Sonically, SA-1 V2 is smooth, lean and relaxed, while PB5 has a lively, detailed, contrasty and colorful sound, with a strong resolution technical performance. iBasso PB5 also has that specific tube post-ringing which SA-1 does not have. Both AMPs are excellent for what they are, but SA-1 V2 has that ultra-forgiving presentation while PB5 has a vivid, colorful, bright and sharp presentation that renders all the detail in music really well.
Value and Conclusion
It goes without saying that for the 599 USD price tag it carries, Singxer SA-1 V2 offers excellent performance and value, with those 10W of power at maximum being more than enough even for power-hungry greedy headphones like HIFIMAN HE1000SE and HIFIMAN He6SE, or even Dan Clark Expanse, but it still manages to deliver refinement and clarity, with a low noise floor, for driving IEMS and efficient headphones, and with a dedicated high-impedance mode, SA-1 V2 is downright excellent for driving the high-Z headphones too.
At the end of the day, if what you need is a headphone amplifier / preamplifier with a smooth, lush, deep and rich sound, relaxed and forgiving presentation and with a superb builds quality, and a modern, beautiful design, Singxer SA-1 V2 is one of the best you can grab right now, and available with all the popular HiFi sale channels in the whole world.
Product Link
Amazon – https://amzn.to/4dvKGEf
Aliexpress – https://s.click.aliexpress.com/e/_De93Dzf
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Full Playlist used for this review
We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature. I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!
https://www.youtube.com/playlist?list=PL_cjBXGmwSHSdGcwuc_bKbBDGHL4QvYBu
https://open.spotify.com/playlist/5J3oloz8Riy9LxEGenOjQ0?si=979ba4f082414be7
https://tidal.com/browse/playlist/330fd544-8e5b-4839-bd35-676b2edbb3d5
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