IIMO, those kinds of devices are for audio nerds with expensive headphones who (incorrectly) think they are getting better sound quality from a dedicated device versus a $10 dongle. For what you want, I would recommend getting a portable Bluetooth speaker instead. They will cost less and sound better. The better sound will include a wider frequency range, which will mean you can listen at lower volumes and therefore protect your hearing. If you get one that is USB C rechargeable you can (usually) even leave it plugged in while using it like a non-portable speaker.

Tronsmart makes nice little bluetooth speakers on the cheap. They have several nice options. If I just wanted something portable, I would get the tronsmart trip that can be had on AliExpress for $13 if you hunt around. The groove 2 ($20 on Aliexpress, significant upgrade in sound) or t2 mini ($30, only a little nicer than the groove 2) are also nice.

There are also options from soundcore and mono-price that people seem to like but I haven't used them.

PSA: Soulseek is a proprietary protocol created by a Zionist and you should be using Nicotine+ to interact with the network instead.

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No where is one able to download the source code and compile Soulseek itself and the p2p protocol is proprietary, don't fall into a zionist trap.

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Mossad honeypot lmao

Link tracking, &ref= and everything after must go.

I use a Fiio player and an aux cable connected to a portable speaker. It gets very loud. If the mp3 player dies I'm in trouble, though, because it looks like they don't make affordable options anymore.

Get a Bluetooth speaker with an SD card slot !

I think that's going to be a bit of a tall order to get a really good quality small form-factor speaker with a good quality mp3 player as an all-in-one unit.

Am I recalling correctly that you do fieldwork? If so then you might be interested in some of the ruggedized Ulefone offerings – aside from being designed for construction sites etc. and often being waterproof with a larger battery, they tend to boast a much more substantial speaker than any other phone I've come across. But they come at a premium as they are a mobile phone so maybe it's something to put on the horizon as a purchase down the track.

Otherwise my ideal setup would be a Hiby R2 or R3 or a Shanling M0 + a small bluetooth speaker, maybe a small Soundcore or Tribit unit.

If one part of that setup dies then you can replace it, plus there's more options available because independent bluetooth speakers will work with anything.

Also it depends on what size pockets we're talking here. All of this is going to be way above the budget in your post tho.