Buy a 10 db attenuater, this is a simple RCA/RCA or XLR/XLR device the reduces the volume by 10 db. If you are running a RCA cable, let me know via e-mail as I have a pair sitting around for a time in the past when I had a similar problem.
Just so you know, this doesn't change the steps with each volume control turn (or push of the RC). But if you want to try this approach, email me and I'll send you my pair. If it works to your satisfaction you can keep them (buy them). I think the going price for a pair is $50 used (if they are advertised currently for less, you can pay the lower advertised price). If you don't like the results, just send them back to me.