The only correct way to use the transformer inputs on the 828 with line level sources is to use a 20dB XLR pad. :
A DI box like the op asked is also a “correct way” to connect -10dbv Line level sources to a Microphone Preamplifier’s input. The DI will respect both Levels and Impedances
Most DI’s have a PAD at the input, 0db’s for Guitar/Bass, -20db’s for Line level -10dbv (keyboards,samplers) and -40dbs for Speaker Level.
Anyway, connecting a Line level device directly to the Alice Microphone input is also quite nice if you want to distort or dirty up that line level source, expect distortion and a limited frequency response, but it might be nice for specific tasks. The 828 distorts nicelly