WRWSTD

I would start by checking out this site. https://www.ranecommercial.com/kb_article.php?article=2107. They do a good job of explaining the proper way to hook up different types of equipment.

MacAyr, Make sure that the volume slider near the player buttons is all the way to the right.

There is very good information from RANE regarding the "correct way" to connect components with what wire and what connector. Be careful of tying pins together. http://www.rane.com/note110.html

I cannot answer that and will leave that to someone more qualified as far as Switches and the Micro Rendu. I wish you all the best and good listening!

I can dig it. I will say that a digital conversion done within the mathematical limits of the playback engine will make the sound smoother, more realistic and the top end will be less annoying. This is what I went through as well. If the high end is still too much, set the cut-off frequency to 84. This will certainly trim the very high end but leave the rest of the sound intact as set by the other slider adjustments.

The other settings shown happened to be my own for the dac that I use. Sorry for the confusion. However, we all have the adjustable slider for track preload. That is the one I was referring to in the last screen shot. Set the slider for 5376. The screen shot before the last one depicts the settings of the up-sample converter. Set those just as you see them. If you cannot slide it to the values, move the screen cursor into the box and highlight it by tapping the trackpad. Hit the delete key and then enter the number including any comma or periods that you see. Hit the enter key when done with each individual box. Hope this helps.

In my case, it would look like this

8GB is fine. 5376 will fit. It is well under 8.000GB at 5.376GB. Just drag the slider until 5376 is visible.

OK, now to address the OP's original question of how do I eliminate the treble harshness.... Well, here is how I see it. It has been my experience that a lot of the harshness etc, that we hear is actually some form of distortion. Reducing treble response can reduce the effects but the distortion is still there. My proposed adjustments seem to make a good compromise to the playback engine used. Using these numbers (no deviation) with the Track preload number of exactly 5376 seem to make a good compromise. Please, tell me your impressions.

Specifically use 5376

If the computer had 16GB of memory, I would set it to 10752

This may sound odd to some of you A+ users, the memory allocation has a small effect on the sound. It is how the computer runs and is very repeatable. I had run tests with different macs running different memory size, hard drives, and different OS. The result was quite a surprise for something that was only used to allocate memory. It is also interactive with the earlier screen shot I had posted. To make a long story short, a lot of listening took place and these settings seem to work well.

Because I do not have a Micro Rendu, I was assuming that the slider in your screen shot that shows 6528 was adjustable.

OK, I mis-spoke. It is called Track Pre-load. Slide that over to 5376 and give a listen. I will be interested to see if you hear a difference.

Try setting the A+ buffer size to 5376 and see if you hear a difference.