Keeping this review short and crisp. I own a 50 inch VU TV (2015) and a Sony HiFi music system (MHC VX-777, Malaysia) back from 2002~2003, costed around INR 30k back then. The only reason I've kept the music system is because of the exceptional sound it produces under any circumstance. The speakers are wooden and it has surround speakers as well. I absolutely love it and ofcourse a lot of childhood memories attached.
Coming to the connections, I took the optical out of my TV to the FiiO D03K, then from there connected the RCA to system. And voila, the sound is amazing! Now I can use it while watching TV (D2h) as well as web series via Fire TV stick. The output is good enough for day to day usage, though not the enthusiast quality if you have those expectations. The price I feel is justified given the build quality.
Products that I used for the entire build:
1. FiiO D03K - Purchased from Headphonezone
2. USB Adapter - https://www.amazon.in/gp/product/B07HQCT46F/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
3. Toslink cable - https://www.amazon.in/gp/product/B005LJQMZC/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
4. RCA Cable - https://www.amazon.in/gp/product/B077GS3SSG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

Please note, the box contains the micro USB chord but NO adapter. Use any 5V/1A charger to power this up. I purchased a dedicated adapter and have linked the same above, it's cheap and works like a charm.

Thanks to HeadphoneZone for great delivery and device experience. Cheers to all!

PS: I'm not promoting any of the above products, just trying to make everyone's lives easy by providing the entire setup details.

Thanks to headphonezone for bringing this quality product with warranty support, to India. And quick shipping.

I haven't tested the Optical input or RCA output. My primary use case is to draw digital audio out of my 2016 model TV using SPDIF (Coaxial) and convert to analog by a decent chip. This D03K does the job. The interfaces are clean and the build is good enough to be kept discrete. The sound quality is very clean and without any artificial articulation.

I am planning to connect a Power amplifier and just a pair of bookshelf speakers to complete my TV setup. My old TV doesn't have Dolby audio or any other surround format. So this D03K is good enough

Please note, this DAC doesn't support Dolby Audio or any other codec. If your TV has Dolby support, this DAC is useless, and better get a proper DAC which has all codec support.

But, for simply bringing the best audio out of a old TV which has a SPDIF or a Optical output, this is the best DAC which does only the essential task.

Also, please note, TVs don't support volume control for lineout. This D03K also doesn't have volume control. If you're connecting it to a headphone amp or power amplifier or a soundbar, the volume control can be done only in those. The TV remote is useless for volume control with this connection setup.

Very much pleased with the quality of output, this little DAC produces. I bought this to pair it with my TV (optical) and tower speakers(RCA), as my speaker's output was too low through its Bluetooth mode, when enjoying OTT platforms and other net based services. The only issue I noticed is that, there is no option for an HDMI input, which I heard, is superior than both coaxial and optical input options provided with the DAC. But still, the audio output this guy produces is crystal clear and top notch.

My TV doesn't have the option to choose 3.5 mm or inbuilt tv speakers as the audio output while the headphones are plugged in. So i purchased this to connect my headphones to the tv using co-axial. When compared to what fiio was giving to my headphones, the TV's 3.5mm was loud and clear. I connected my media speaker which has an amplifier, the output was as expected. Maybe using an audio amplifier after fiio would work out, but it's too much of a hustle.

It does well what the manufacturer mentioned.

I used to hear music using mobile, DVD and lap out as audio output. This d03k sounds well above the mobile and lap headphone out. But, not as good as a DVD player in terms of imaging and dynamics, even though it's mp3 @ 320kbps or m4a @ 512kbps (yes... DVD players are still very good for the money we spend)

The good thing with d03k is it's flat so it doesn't sound bloated as my mobile or laptop and clarity is better than DVD (maybe because of the lossless source). I connected the DAC with my tv btw.

And it's the third purchase from the Headphone zone and will continue in future. The experience is good as always.

I don't know if it happens or not but, to my ear this DAC sounds little bit better after some hours of usage. And it doesn't come with power adapter and optical cable. That maybe cost another 100 or 300 if you want a better quality rca cable and optical cable.

I recently bought it to use it with my LG C2 and some old 3.5mm jack speakers i had. Works pretty well and enhances the loudness.

First day experience. Firestick into tv toslink to Fii0 into Philips Valve amp into original philips 12" 2 way speakers. Music source 24 & more bit 320K high resolution FLAC internet radio. Yet to listen on my JBL headphone amp, with Fii0 dual driver headphone., and integrated stereo amp. sound qualty flat over frequency spectrum. No sub reqd.,It uplifts the tonal quality, hence produces bright sound. Happy to be associated with your team.
This is my 4th Fii0 product