Analog to imac

I want to hook up my IMac to my Freya Shiit preamp.
It would take a USB to an analog going into the preamp.
Any suggestions?
Budget is around 250 dollars.

Thank you for your input.

Since you have a Shiit preamp one of the Shiit DACs between the iMac and the preamp should work fine. Or any DAC with a USB input that you prefer, any DAC will have analog output that can be connected to the Freya.
A HiFi man EF2A would work awesome it has USB and a pair of RCA outs plus its TUBED! come on man! $150 new, and its a headphone amp!
Matt M