I would like to tell you about these online radio stations I listen constantly to for the past 5+ years.
As well as describe a way to listen to them in premium quality (MP3 320/256 Kbps or AAC 128 Kbps) with no ads without paying anything. You can skip to the end of this post for actions and a website to automate them.

AudioAddict is a company behind the 5 popular Internet radio stations (with DI.FM being the oldest and most well-known).

A quote from RadioTunes website that is true about all other stations as well:

Unlike other internet radio companies, we actually have Channel Directors – real people who know good music – for each of our stations. They find the best music in each genre and create playlists that give you the music you want to hear. RadioTunes also specializes in offering these curated channels for niche music genres that are hard to find anywhere else.

1.

Digitally Imported streams the world's most addictive electronic music. Our hand-programmed radio channels feature world renowned Artists, DJs, and the Hottest exclusive shows. Tune into over 35 radio channels for the hottest electronic music from genres such as Trance, House, Dance, Lounge, Chillout, Techno, Ambient, and many more.

2.

RadioTunes.com features a wide variety of high quality free streaming radio channels. Find your favorites among the best of each class - be it New Age, 80s, Smooth Jazz, New Age, Top40, Hip Hop, Oldies, 70s, Reggae, Lounge or many others inside.

3.

ROCKRADIO.com offers 35+ channels of the best rock music available. Each one is hand-programmed by a channel manager who is an expert in that style. Find all your favorite rock styles including Classic, Hard, Metal, Modern, and many more!

4.

JAZZRADIO.com was launched in 2009 to bring excellent jazz music to passionate fans around the world. Today we offer over 35 channels of curated jazz music ranging from the earliest days of Jazz, to the swinging sounds of the Big Bands and the classic era of Bebop, through the more modern styles of Smooth Jazz, Current Jazz and today's Contemporary Vocalists. We’ve also curated the best international music on channels such as Latin Jazz, Gypsy Jazz, and Bossa Nova.

5.

ClassicalRadio.com was launched in 2015 to bring beautiful classical music to passionate fans around the world. Today we offer 40 channels of curated classical music ranging from the Medieval Period to contemporary performances by todays brightest artists and composers. Our channel selection includes curated selections from the world's most renown composers, a variety of classical periods, favorite instrumentals, theatrical performances, and orchestral works.

Mobile apps for Android, iOS, BlackBerry 10, Windows Phone.
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So how to listen to it for free and in best quality? The answer is, using 7-day premium trial accounts.

It's very easy to make one manually. If you create it on one site, you can use it on all 5.

1. Go to http://www.di.fm/trial
2. Click "Start 7 Day Trial"
3. Click "SIGN UP"
4. Enter any random e-mail (no real one needed, but type some existing domain like @gmail.com, @aol.com, @msn.com)
5. Click "CREATE FREE ACCOUNT"
6. You should now be logged in and redirected to http://www.di.fm/member/premium/trial
7. Click on "Start 7 Day Trial"

That's it, now you can listen to all of the channels without ads and in best quality, either from the website or using mobile apps. After 7 days, you need to repeat these actions because your trial subscription will expire.

However, there are some issues:
1) You can't download a full premium playlist with every channel, only with a single channel or with your favorites. So you need to check every channel as favorite and then download them as a playlist.
2) You can't transfer your favorites from one account to another.
3) You can download only .pls playlists, but some devices recognize only .m3u
4) You get a playlist with random servers out of 4 total. Some of them are closer to you geographically (so you would want to use them), but the website won't allow you to specify it.
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To overcome the above limitations and automate the process of creating a new premium account every week, I created a website:

Which stands for AudioAddict Premium Playlist GenerAtor.
If you don't already have an account, check the options and click "Generate".
Within seconds you'll receive a .zip file with all your playlists, as well as information about the generated email, password, name and expiration date.
You can use this email/password on the websites and in the official mobile apps.
If you had an account before, you can type it in the "Account" panel and click "Check" to see if it's active or expired and get the expiration date.
If it's still active, you may just want to generate up-to-date playlists with your settings, choose "Don't create a new account" and "Generate".
If your old account had favorites on any of the 5 stations, they will be automatically transferred.

If you want to check what server is best for you, open cmd.exe and type:
ping prem1.di.fm
ping prem3.di.fm
ping prem1.radiotunes.com
ping prem4.classicalradio.com
etc.