Hi Patrickamory - I have, but do not currently own the IO Sig. The IO Sig I owned did not have the volume control. My suggestion was to turn down the gain on your IO by using the internal jumpers, connect it direct to your amplifier, put on a record that starts off quiet - one you are VERY familiar with, and listen.
For me, the experience of hearing an IO Sig with NOS tubes direct to an amp was extraordinary but I couldn't live with no volume control - I tried.
Mick (the manufacturer of Supratek products) told me that his Cortese phono would, "Put the IO in its grave", so I purchased a Cortese - which is an "integrated" phono/linestage preamp.
The Cortese did not put the IO in its grave but is still very good - good enough for me to live with but keep in mind, after I listened to the IO direct, this hobby became more difficult - I became jaded and simply accepted that there was no silver-bullet or perfect solution. It is almost impossible to quantify how much better the IO sounded without a line stage or any volume control whatsoever.
Of course, I pondered having the volume controls & line level input added to the IO but then struggled with the lack of a remote and the inconvenience of two volume knobs.
Maybe a transformer based passive would be better? Silver Rock or Bent? I dunno...