Tidal music to analog preamp

I like Sonos Connect.  Great user interface. About $350 new with built in DAC. At a later date, if you like, there are various upgrades, such as a better DAC. 

you can do it from your MacBook.  I ran mine off an ipod touch for a few months...

I have a Schiit Bifrost Multibit Dac, which sounds great and doesn't cost much, and should outperform a Sonus by a wide margin. I assume a MacBook Air has USB (I'm a PC guy).

The cheapest fastest way to get the sound from the MacBook Air (MBA) to the preamp is to get a stereo plug mini to RCA cable of a length that will allow you to put the MBA at a location where you can use it but still reach the preamp. (Assuming you have RCA aux. inputs available?)

Other posters, having read this, will chime in and tell you you will really need a DAC from the USB output of the MBA with standard RCA interconnects to your preamp. And you do. Or will want to. 

But there are dozens of DACs to choose from and you asked easiest and little cost possible. Getting the cable and running the output of the MBA to the preamp will work. For now. Then when you do get a DAC, you will (hopefully) notice an improvement in sound quality. 

The Audioquest Dragonfly DAC products or similar USB headphone amplifier products will work provided you use the line output setting on the USB headphone amp. You'll still need to use that stereo mini to RCA cable. 

Good luck.