I own both the BTR3K and BTR5 so will compare both against each other.

My use case: Since new phones don't have 3.5mm output, I wanted something to play music, watch videos and take handsfree calls on my phone. I was only going to use either an earphone (Sony MDR xb55ap) or a regular headphone (ATH M40X).

Build quality - Amazing. No sharp edges, looks modern, small size, light weight. Can be easily clipped to shirt collar with the provided plastic clip. It is so light and small that in a few minutes, you forget it's even there. BTR5 is twice bigger and heavier. It is also small but not so small & light that you forget it. It is another device that you have to carry in your pocket.

Sound quality - Waaaay better than anything found in a phone/laptop/tab. If you haven't heard any other DAC/Amp so far, this will be audio nirvana for you. Good music separation, tight bass, wide soundstage, clear vocals, no background noise/pop.

Microphone - The microphone works as it should. If your earphone has mic, it picks up that. If it doesn't, it uses it's own mic. But since it will be on your shirt collar, it also picks up surrounding noise. So either use earphones with mic or bring it closer to your mouth which looks weird especially to others or take calls in a quiet environment.

Battery - Lasts a whole day easily from morning till late night.

Bluetooth range & latency - Depends on codec being used. LDAC has shortest range (one room only) but best audio quality. AAC has longest range (3bhk house) but worst audio quality. aptX is somewhere in between so pick as per your need. I mostly use LDAC and the latency/lag/delay is barely noticeable. It is there but only if you really notice. Pause and play again if there is delay in videos.

Value for money - Would have been perfect if Fiio had priced it 1K less but even at the current price, it is the best in the market for what it does. So okay there just not great.

Comparing with BTR5 - This is where it gets interesting. BTR5 has an objectively better sound quality. It is slightly sparkly in treble, has tighter bass and perfect timings on vocals and beats. It makes songs way more enjoyable and lively. BTR3K is laid pack in perspective, it is slightly warm, less tight bass and is loose on vocals and beats. And this is where it boils down to what you need. For long listening sessions (>1 hour), I prefer BTR3K. BTR5 sounds lively and immersive but it is so prominent and "in your face" that you can't focus on anything else. So, for my use case, where I wanted something to play music/videos on phone for long hours and still work or read/cook/run etc., the laid back sound of BTR3K is much better. It doesn't get fatiguing even after hours of music and the slightly warm sound is relaxing for videos/calls. Get BTR5 if you want to close your eyes, sit in a sofa, drown in music and do nothing else. Or if you have power hungry headphones. I now mainly use it as a DAC for my speakers in which it excels. If you plan to casually listen and work/study/run etc. BTR3K is better as its less revealing and fatiguing. BTR5 is better than BTR3K in analytical sound quality but it depends on your listening use case. Fiio has very cleverly designed and placed these products. BTR5 is well worth the extra price IF you have use for it and don't mind the DOUBLE size/weight/presence.

Headphone zone experience - Flawless. Delivered on time and the product is new. I even received some audiophile songs recommendations which is a good touch and sets them apart. Delivery updates were on time and accurate. Have been ordering from them and will again in future.

This small amp/dac combo has absolutely changed how i work and listen to music. Being a bluetooth adapter is such a big plus, it does not limit me by the length of earphone or headphone, and the fact that you can use the inbuilt mic of the eaphone/headphone is a major plus, that means you dont have to clip the adapter near your neck, you can just toss it in your pocket and chill. The difference is there when you use it as a usb dac, it sounds way better than the normal audio output. Ability to connect 2 devices and switch between them effortlessly is also useful. A tip - upgrade the firmware version to 1.3 , then you can reprogram the volume up and down button, to a limited extent ofc. Very happy with this product 10/10 will recommend to anyone.!

It's just amazing to hear what this little dac can do! I use it to wirelessly connect to my JBL stage a170 tower speakers via an amp. The amount of soundstage and details which this added was just mmmmm...apart from that I love the touch of uniqueness from headphonezone, it's my first purchase from here and it was a great one.

I was really skeptical about the power output figures, weather it would be able to drive my EX1 and Aria's however I was pleasantly surprised that not only can it drive them but there room to spare and that is out of the single ended output. You obviously cannot compare the overall sound quality to a desktop amp/dac but it does the job. Bluetooth connection is pretty stable upto 10 m beyond which it starts to distort. Hats off to Headphone Zone and Bluedart for the really fast delivery. I have bought quite a few products from them over the years and they do not disappoint with their delivery and customer service.

I purchased this for outdoor listenning with my Legacy 3 IEM. I used to have a Lypertek Tevi TWS but after their battery died suddenly I decided to go with a bluetooth DAC instead of a new TWS that sacrifices on audio quality. It's perfect for my use case and its bigger brother (btr5) has rave reviews all over the interwebs.

I have loved the sound out of the 3.5mm output and I did notice that I need to turn the volume up quite a bit. But this also supports balanced output and that is supposed to have a greater audible range.

Few quirks that I didn't like:
1. The battery level follows a step function of 20. I have never seen any battery percentage that is not a multiple of 20 yet.
2. Unlike the btr5 there is no screen and instead there is just an rgb led. Not a big deal for me but seems like there's enough space to show the volume level at least.

Audio level should be increased. Other than everything is good.

One step forward in audiophile journey.
Can't tell in words
We Have to feel
(Bhuke ko khana miljaye aisa hi kuch samjho)