Itching to upgrade preamp...

PS audiojan OP:

Also to try what I posted above, try putting everything through the  PS Audio PP12  except for the XA60.5.

In every A/B experiment I've done with conditioners and power amps (especially Class-A) they always sound better direct into the mains.

As any conditioner will have some sort of series impedance and this is a no no for an amps power supply if it's to remain nice and stiff. 

Cheers George

audiojan OP
I’m thinking the preamp might be the weak link at this point... Today I’m using a Pass X0.2 preamp.

I would go direct, as it’s the most transparent, dynamic way with no coloration distortions from any preamp.

You can connect direct to the XA-60.5 using "balanced" interconnect.
And the PSA DirectStream Sr has nearly 3v output!! and Pass XA only needs 1.1v for full wattage output, as you can see you have too much gain already!! without adding even more from an active preamp as well.

From PS Audio
PS Audio DirectStream Sr Resolution perfect volume and balance controls

Designer Smith perfected a 100% bit-perfect volume and balance control that’s built into DirectStream, enabling users to control the output level when feeding directly into a power amplifier.

That the volume control is completely bit-perfect means there is no loss of resolution for any volume setting, a feature unique amongst the majority of DACS in the world today.

NB: The ability to eliminate the preamplifier in the system without any resolution loss is a major benefit to DirectStream’s outstanding musical performance.

Cheers George

I used to go direct from the DS Sr to the XA60.5, but inserting the preamp added quite a bit more space and drive.

Sorry but it’s impossible, for the XA60.5’s 1.1v input sens, 30khom input impedance to "load down" and reduce the "drive" from the output of the DS Sr’s 3v 100ohms output impedance. All a pre can do in this case is add coloration/distortions, as well as the extra set of interconnects
Even Paul McGowen has said so  "The ability to eliminate the preamplifier in the system without any resolution loss is a major benefit to DirectStream’s outstanding musical performance."  

Going through the P12 the XA60.5 yes it looses a bit of low end slam

And this is telling you something that Nelson Pass would even object about.

There are other things you need to look at "if" both these so called apparent "fixes" are better to you.

Cheers George