Dayton Audio DTA-100ST question

I've got a Dayton Audio DTA-100ST amplifier that works great, however I do not like how the volume control adjusts the volume in larger steps than most volume controls.

I currently use a Schiit Saga S preamp to control the volume, but I want to do away with that as it seems dumb to use a preamp when I shouldn't need one.

Is there a way to modify the Dayton amp to provide more of a fine control over the volume?
 
Any idea what the input impedance of this amp is?

The manual doesn't specify it and a quick Google search doesn't show what it is either.

I've decided that I will install a stereo volume control in a metal case along with a switch to provide a mute function and need the impedance so that I know what value of volume control to use.

I'll likely find a metal case with a similar finish to the amplifier.
 
Well I've traced the wiring in the amp and the volume control varies a DC voltage from 0-1.8Vdc and it connects to the Bluetooth board so most likely there's a programmed chip on board that takes the analog input and changes the volume in steps.

Sooooooooo............there's nothing I can really do to the amp within reason to make the volume control better.

I will indeed need an external volume control and will need a mute switch as well given that sometimes I need to mute the audio when on the phone or someone comes to my desk and asks me a question.

Will look and see what's available before I go making my own as I want something that looks decent.

While the Saga S works just fine, I'd prefer it be back at home on my tube amp as the Sony preamp I am using doesn't sound quite as good in the treble as the Saga S does.