Here is how SR25 pairs up with various IEMs, earbuds, headphones. For the reference, I indicated the volume level in (v). Each one was tested with a balanced cable.
Empire Ears Legend X (v70) – wide soundstage expansion, not super wide, but decent. The typical L-shaped sig of LX in this pair up becomes more V-shaped. Mids are there, clear detailed natural, but bass is ear-shattering with a very powerful deep sub-bass rumble and strong rounded mid-bass punch. The bass is complemented by sparkly clear treble. Perhaps, the signature is more reversed J-shaped. And that bass slams very hard, making LX woofers to rattle your brain.
VE Sun Dice (v92) – wasn’t sure how SR25 will be able to handling these 180ohm earbuds. The sound is still open and nicely expanded since earbuds are sitting on top of my ears. But the sound sig is a little different, not as balanced like in some other pair ups, but rather more mid-forward. Bass is slightly attenuated here, not rolled off, but just attenuated. Mids/vocals are clear, organic, soulful, smooth. Treble has a nice well controlled sparkle as well. Personally, I preferred Sun Dice pair up with sources where its signature is more balance, but if you want to focus more on vocals, this will be pretty good.
Campfire Audio Solaris OG (v43) – nicely expanded wide soundstage, with a little more out of your head expansion, giving it more depth than width. Overall sound sig is balanced with a smoother tonality. Bass has a nice analog flavor with a deep rumble and an average speed punch (attack is a little slower, typical for DD performance). Mids are smooth, natural, detailed, not too revealing. Treble is well controlled, not exaggerated or fatigue.
Campfire Audio Andromeda (v45) – there are a lot of similarities in this pair up with Solaris. The soundstage has a similar width and depth, with more out of your head depth. The signature is also balanced and the tonality is smooth, but a little more revealing. Bass has a good rumble and decent punch, but the quantity feels closer to neutral here, definitely not as elevated as Solaris. Mids/vocals are smooth, natural, and at the same time with a better retrieval of details than Solaris. The same with treble, I hear more sparkle with Andro than Solaris.
64 Audio Trio (v66) – wide soundstage expansion, actually soundstage is a little more holographic in this pair up. The signature is nicely balanced with a natural detailed tonality. Bass is very powerful in this pair up, going deep with a textured rumble and faster mid-bass punch. Mids are natural, detailed, with an excellent clarity, but the presentation is pushed slightly out of your head. Treble has nice sparkle, non-fatigue, and still with a good sense of airiness.
64 Audio U12t (v66) – I hear a wide soundstage expansion, with a little more out of your head depth. The overall signature is balanced, with a slightly mid-forward presentation. Bass has a good depth and mid-bass punch, but it’s closer to neutral in quantity. Mids/vocals are clear, natural, detailed, with a little more forward presentation in comparison to Trio. Treble is non-fatigue, well controlled, clear, and with less sparkle than Trio. Actually, with SR25, Trio sounds more fun, while U12t is more laidback.
Beyerdynamic T5p 2nd (v79) – wide soundstage with more depth than width. Nicely balanced signature with a clear detailed tonality. Deep analog bass extension with a textured rumble and fast mid-bass punch. A little thinner neutral-bright mids/vocals with a nice layering and separation of sounds. Good treble extension with a nice well controlled sparkle and airiness. Surprisingly good pair up, especially impressive bass extension.
Meze Audio Empyrean (v91) – wide soundstage expansion with a little more depth than width. The overall sig is balanced and tonality is smooth, but the sound presentation is more laidback. This pair up is not exactly what I’m used to hear with Empyrean, bass doesn’t extend as deep or punches as hard, and mids are a bit too smooth and laid back. Treble is very good, detailed and sparkly. SR25 has no problem driving these planar magnetic headphones loud enough, but not to their full potential.
The bottom line, can it drive earphones and headphones loud enough? Without a doubt it can! I was even able to drive my open back 470ohm impedance ATH-R70x at 124 (out of 150) volume. But, with more demanding higher impedance headphones and some planar magnetics that need more current, I don’t think SR25 was able to push them to their full potential.
Wired and wireless connections.
Besides being a portable DAP, you can expand SR25 functionality as a transport to drive external DAC/amp, to use external AMP, or to turn the DAP into usb DAC. And of course, you don’t have to be limited to wired headphones, and can take advantage of Wireless Bluetooth connection.
Tested Bluetooth Wireless with various headphones, SR25 paired up within seconds and had the acknowledgement message on the screen that it was connected using corresponding codec. I was able to change volume from SR25 and from wireless headphones, as well as control the playback and skip tracks remotely. Wireless connection worked about 20ft away from SR25 in open area. This is not the strongest performance like in SPK or SP2k, most likely due to reduced power of BT transmitter to save battery life in SR25.
Connected to FiiO E12A, I had to select Line Out from notification bar and was able to control the volume from both external amp and SR25. If you need to color your sound with an external amplifier or need to drive more demanding headphones, access to LO is convenient.
USB Audio Out.
Connected to Lotoo S1 USB DAC/amp using Lotoo’s provided cable. In notification bar of SR25 have to be sure External USB is selected to enable USB Audio mode. Volume was fixed on SR25 at 150, and I can adjust it from S1. Very clean and transparent sound based on sound characteristics of S1 DAC/amp while using SR25 as a digital transport.
Recognized right away by my ThinkPad T480s (Win10Pro). In notification bar of SR25 have to tap USB Mode to select DAC. Volume can be adjusted from Laptop or SR25. No need to install any additional drivers, and the sound was typical of SR25 headphone output.
Every time I get a chance to review A&K DAPs, I get reminded how loyal their fanbase is. Often after receiving different DAPs for review purpose and mentioning about it on FB or in corresponding Head-fi thread, people ask me about comparison to other DAPs in the same class, including if the price difference is justified. When I acknowledged about receiving SR25 for review, most of the questions I received were from existing SR15 owners, asking for comparison and if it makes sense to upgrade. That was exactly the reason why I asked A&K for SR15 loaner in addition to SR25, to answer the burning question about side-by-side comparison.
Similar to SP1000 vs SP2000, price of SR25 remained the same as SR15. But SP2k upgrade was more about the finetuning, while SR25 upgrade was a step forward. SR15 and 25 share a similar sound sig, and that’s about it. As it was mentioned in the review, technical sound performance of SR25 is superior to SR15. And on top of that, you have a bigger higher resolution display that looks night’n’day in comparison to SR15, usb type-c (vs micro usb), addition of LDAC (not holding my breath for 4.4mm, but LDAC broke the ice), stepping up to DSD256 (vs DSD128), PMEQ with a more noticeable sound adjustment, and the battery which now lasts almost 22.5hrs (vs 10hrs). For the same price as SR15, it is no-brainer!