ampex 351 mic input

I just picked up a recapped and modified ampex 351. It was only $170 can, and I couldn't pass it up. It's been setup as just a preamp. But the problem, is that the guy I bought it off of doesn't know anything about it. Only, that a local reputable tech shop did the work.



I've tried it out, and it seems to be in very good condition.



I have a question about the front panel 1/4 inch input, and the line input on the back:



The front mic input is labelled "instrument input" with a sticker label. Isn't this normally the the mic input? And if so, what is the best way to wire up a dynamic or ribbon mic?



Thanks.

ampex 351 mic input