I was previously using a small & cheaper BT 2.1 channel power amp with the same Texas Instrument's TPA3255 chip. However, Fosi Audio BT30D Pro works much better than the previous one. The difference is obvious. The only part I can point out is that the mid-range is slightly weak. It's a really good class-D power amp for this price range.

I had owned both the HiFiMan Sundara and the Edition XS few years back - but as with all things audio - started to yearn for a different taste and so moved towards high impedance headphones and tube amplifiers - selling my HiFiMan headphones to buy new gears of interest :-) Recently felt the urge to get back into the planar sound. But didn't want to invest too much to start with - not being sure whether I'd find the experience as enjoyable as the first time. The 400SE fit the bill nicely and I'm glad to report that I've not regretted my decision one bit. Thanks TAS. Greatly enjoying the set. Pairing is critical though - started with the iFi Zen One Signature DAC + iFi Zen Can - but felt something was missing - switched to the Cayin RU6 and immediately got back the exquisite detail and imaging/instrument separation that planars are famous for.

The audio quality is very good. I hear it at neutral settings and use it more than 12 hours a day..It isn't tiring to the ear and sound awesome

For the money, this almost delivers similar to chopin at mid volume levels

My setup: Thieaudio Monarch MK3, paired with this Sony 707 unit, and music played from Apple Music.
Comparison with: my previous DAC/Amp Jcally AP98, Shanling M6 Ultra

Its been months since I've been using the 700 series portable music player of Sony's and finally got myself up to reviewing it.

So first question: why a DAP? For months, as I was using my AP98 dac/amp connected to my phone to listen to music, I came to realise a very obvious and quite irritating issue: the type-C connector is a nightmare when its wobbling in your pocket. It is not designed to stay tightly fixed. Mainly used for charging and data transfers, I don't think the engineers behind in ever factored the port being used to play music through an amp/dac. And when it is used to play music on-the-go, you'll reach a point when you'll constantly find it getting loose and disconnecting with your device. Especially if you listen to music while doing a lot of walking like I do. There's no point trying to listen to audiophile grade tunes when they are getting constantly disconnected. So, a change had to be made.

For those who don't know, a DAP is a full android environment in itself. Its basically if a phone was designed for one thing, and one thing only: to play music. You can download any android app on it (although it doesn't have a sim card), but you really shouldn't. These things chug a lot of battery to produce the sound that they need to. Slowing them down with other apps is not recommended.
Anyhow, how did this portable music player solve my issue? Well it has the typical 3.5mm audio jack, as well as the 4.4mm balanced output. Connect your IEM/headphone to them directly, and you say goodbye to any "loose" connections. Uninterrupted audiophile sound = happy audiophile.

So how is the device itself? Quite big actually. The length and width is similar to that of your phone, and its much thicker. Will need its own dedicated pocket. I had to do a bit of juggling of my pocket items when I got this, so that might annoy some people. After all pocket spaces are sacred, and this unit is going to force you to change your habit of what goes in which pocket.
So having had my pocket sanctity shredded, there is also another nitpick of how edgy the device is. You could literally use those metal-finished corners as a weapon. Apart from that I'd have also liked the buttons to be a bit more protruding, but thats fine. You don't usually change volume too much anyway.
So those slight negative bits out of the way, the device itself is very nice to hold. Has a gripping pad thingy on the back that makes it very good for my sweaty hands. The display is good, android environment is very operable. Its not your latest gaming mobile phone fast, but much better than old mobile phones.

Okay now that the boring bits are out, lets get to the real thing: Sound!

This is the first sony device that I've used, and now I absolutely get what the "Sony signature" means. Very musical. Very crystal. You'd expect such a signature to be more favouring towards the higher frequencies, but that's not the case. The device is actually slightly on the warmer side, but you can almost miss it because of how neutral the signature is.
Thanks to the Audio Store I've had the opportunity to try out lot of dac/amps & even DAPs, and this has without a doubt been the most neutral sounding unit I remember.

The resolution is brilliant. I mainly use the Monarch MK3s which are already known to be extremely detailed, but only after using this DAP did I feel that I was really starting to reveal the potential of the MK3s. In this department, its hands down better than the Shanling M6 & my old AP98.

The amplification might not be up to everybody's taste, even though this unit DOES have the High Gain option. You might have to turn the volume really up if you have something with very high impedance. Mainly talking about IEMs though, it should be able to play anything.

Where I feel that this player slightly lacks is the richness of sound. Sony has a very clear, detailed sound, but it can sound somewhat leaner, especially when compared to Shanling M6. Especially for someone like me who mostly listens to instrumental soundtracks. Even the little AP98 with high gain, and connected to a computer has a more voluminous sound. It is why I almost ended up picking the Shanling, but immense thanks to The Audio Store for letting me try the M6 unit for an entire day, after which I quickly realised that it was too bassy for me.

Overall I'm extremely happy with the purchase though. This is something I know I'll value for a very long time, even after I maybe try some other DAPs, because of how balanced the sound is. Sony's signature has grown on me, and I'm certain that some songs will only sound good to me now with this tuning.

Once again, big, big thanks to the Audio Store team for being patient & giving great advice for me to make the right decision.

Quality as expected within the price range.
Excellent delivery service and nice customer feedback system.show how sincere you are towards your customers satisfaction. very happy to shop with you definitely come again and refer your brand to others.

It feels irritating at the beginning since we are not accustomed to that much details but after 2-3 days it feels awesome...however not recommended for gaming(BGMI)
Only issue is the its hard to use it in Type C android phones since you have to buy high quality adaptor for good music experience which cost around (1.5-2k)

As my ear holes are small, many earbuds tend to drop off. but with this SpinFit eartips, there is now a snug fit and the earbuds do not fall off. What a relief.
Good product and recommended for people having small earholes.

My sound preference- I like a balanced, musical, natural, and fun sound. I dislike a basshead sound as well as a neutral, dry, and clinical sound. I absolutely hate peaky, spicy, and treble-intense sound; cannot stand it for more than 10 seconds. I own a wide range of IEMs like 64 Audio Trio, Final A8000, ThieAudio Monarch MKII, 7Hz Salnotes Zero (v1), and many more in between.

Opening notes: I burned in the P1 Plus for about 8-10 hours and found that the sound (especially the treble) settled well after that. The overall sound became more balanced and mature without losing its planar flavor.

Tin HiFi packaging and unboxing is very simple and classy (less is more). The case that comes in the box is especially beautiful. The P1 Plus is a very very small IEM with a very very big sound! It is so small that I can comfortably use it while laying down on my side. There's no weight or pressure build-up even after 4-5 hours of continuous listening. I forget it's in my ear.

Chain: OnePlus 7 Pro -- iFi Hip Dac v1 -- Kinera Leyding cable 4.4 mm -- Tin Hifi P1 Plus -- SpinFit CP-100 ear tips.

The Chain mentioned above is pure bliss! This is as close to a reference, uncolored, and yet musical planar sound that one can get. Seriously, you need to hear this chain to believe how good it is! I was floored the moment I heard it and have been listening to it continuously since the past 3 days now. 'Pure planar sound' is the theme and this chain continuously reminds me of my Hifiman Ananda. The male and female vocals take a slightly forward center stage with a lovely body to them, the bass is very present, wonderfully pleasant, full-bodied, controlled, and yet it is decidedly fast and planar. It is more mid-bass focussed. The treble and air are to be heard to be believed. Every sound, supporting vocal, and squeak is heard. There is no sibilance and listening fatigue whatsoever on this chain (I know that all the reviews say the P1 Plus has a lean sound and is sibilant). The imaging is superb as is the layering. The Soundstage is very deep and wide. Instrument sounds are heard all over the area between far left to far right with good perceived depth. You absolutely must listen to this chain.

Additional notes: I strongly recommend upgrading to a good 4.4 mm balanced cable (not very expensive or anything but a good one; e.g. Kinera Leyding) and the 'SpinFit CP-100' or the 'Moondrop Spring Tips' ear tips to realize the true value of the P1 Plus. With the Spring Tips - you can go a size up. I usually use M size with all my ear tips but with Moondrop Sping Tips and this IEM, I use L and find it more comfortable while giving a better seal.

Many thanks to Pritam for recommending these to me. They're an invaluable part of my IEM collection.

Perfectly balanced, awesomely sounding earphones.

Mid-Bass and Vocal centric.

Sub-bass is clear.

Treble is not too sharp but sounds good.

Conclusion: More value for less money.

Finally got to hear HiRes. Thanks!

It was very good and it retains its own position even after heavy usage

excellent

Superb