Recording from an integrated amp without tape loop

I use a few different tube integrated amps. They have normal inputs and a Pre-In. Non of them have a tape loop. I like to record vinyl to an old reel to reel or digitize through and ADC to my computer. Without having a tape loop, how can I do this? Is there any way?
If you have a seperate phono preamp you should be able to plug that directly into your reel to reel. You'll need it to have adjustable gain, though. If not, you may have to go a different route.
Yes, a phono preamp is the way to go. Many units have selectable gain and cartridge loading. Try The Needle Doctor or Audio Advisor for a wide range of options, including a few tube models.

Zd542 and Gbart, thanks for your responses. I do have a stand alone phone preamp with adjustable gain and loading. I will try that directly into the RtR and monitor it through the RtR output to the amp.