Pretty inexact Rocket, I know. I had a small piece of double side carpet tape. Put the felt in place and when I was tuned in, she'd reach right around and quickly pull it right off.
I figured that'd be a quick and noticeable change if there was going to be one. Me just sitting there playing songs over time is not very easy for me. As it all would sound good. That's why I wanted to start with finding a noticeable difference if there was going to be before moving to longer term listening evaluation. Inexact, I realize, but I'm satisfied if there was change to be found we would have detected something somehow through all that.
It's how I was able to hear such a stark difference when I put my Schiit Gungnir in. One preamp input came straight from disc player and the other came from the DAC. While playing a disc, I could very quickly switch input knob between each of those inputs and clearly hear the difference. I didn't have long to test and return that DAC under their policy so I was evaluating as fast as I can.
Now that the DAC has had time to settle I can hear a difference so easily. It really changed and so much for the better. If I accidentally left the player playing straight to the preamp input it's dull and lifeless compared to the wonderful openness of the preamp input coming from the DAC.