xDuoo MT-602 is a hybrid tube and transistor head-amp, but this doesn’t necessarily means it sounds sweet and soft…
AIYIMA T5 is a small preamp with integrated DAC, analog inputs, headphone output and a Bluetooth connection in an affordable package.
Burson playmate is a DAC, headphone amp and preamp in one. Read this in-depth review to find out how it handles each of these tasks.
TUBE 06 is a tube preamp with both digital and analog inputs. It’s very affordable too and in this review you can read all about it.