Years ago I had one of those gizmos, a wireless fm transmitter where I'd pug my discman, and use a vacant fm frequency to reproduce the sound. It wasn't very good. I imagine that your mode isn't that much better. Have you thought about purchasing a new, modern head unit that would allow Bluetooth connection for your phone, along with a usb plug?
The convenience of not schlepping cds to the car, and futzing around with stuff is out of the ballpark when using the BT for audio. If you are really into having just about everything available out there, there's the Amazon Unlimited music streaming service, which costs around $5-$10/mo., I think. You get access to millions of songs, hundreds of thousands of albums, any time you want , in the car, at the office, or by your pool. I might sign up down the road, but at this juncture I'm mostly all set with what's available for free with the Amazon Prime. They got like 5 or 6 Horace Parlan albums there, streaming for no charge. Takes seconds to hook up the phone to BT, and off you go. To drop a cd into ITunes on your phone takes about 5 minutes, nothing terrible. But I don't even bother with that, just shuffle stuff on my Amazon Music app, it's more fun imho.