I just ran across this thread and thought my past and recent experiences with Pass Labs gear might be of some help.
My experience is deep, rather than broad, as I have not had the opportunity to compare Pass products to other gear. However, over the past 7 years Ive rolled a number of Pass Labs components through my system (mainly used and factory refurbished): X250, X250.5, X350.5, XA160.5, X-1, XP-20, Xono, and XP15. My speakers throughout the past 10 years have been the Martin Logan Odysseys.
As luck would have it, last summer I had the occasion to make a business trip to Nevada. I took advantage of the situation and spent an afternoon with Mark Sammut of Reno Hi-Fi, who graciously treated me to a comparison of various combinations of the X350.5, XA100.5, XA160.5, XA200.5, XP20, XP30, and XP25. Mark was running the Pass SR-2 speakers.
To my ears, anyway, Nelson and Wayne have been on a pretty consistent development trajectory. As you advance from the X-1 to the XP30, I would characterize the improvements as providing greater resolution (I think the same is also more or less true of the move from the X to X.5 class AB amps). By resolution, what I hear in moving up the Pass preamp food chain is a consistent increase in the black quietness from which the music emerges, an increasing ability to discern separate instruments and voices, better control of bass, and a wider and deeper soundstage. BUT, the magnitude of the differences I heard between these preamps depended on the power amp. The differences are more obvious (and breathtaking) as you move into the larger XA class A amps. IMHO, if you are running one of their class AB X.5 amps (or equivalent) the XP20 will be plenty of preamp. Yes, you will be able to hear improvements in the XP30, but put the extra $$ towards one of the XA power amp monoblock designs, instead.
I would characterize the improvements I hear in moving from the X350.5, to the XA100.5 and up the food chain to the XA200.5 amps as providing increasing amounts of body and 3 dimensionality to the instruments. To use a visual analogy, I would describe the X350.5 amp as providing a crystal-clear, hi-definition image. Using better and better preamps in the Pass lineup brings higher and higher definition, but turning up the volume simply makes that hi-def image brighter and brighter, and it remains, in essence, a 2 dimensional image. The XA amps take that hi-def image and turn the pinpoint voices and instruments into individual 3-D holograms of the real thing. The bigger the XA amp, the more palpable the holograms. With these amps, turning up the volume is like moving your seat in a concert hall closer to the stage. The soundstage reaches out and envelops you.
In my case, I felt that my system was better served by keeping my XP20, busting my budget, and trading in my X350.5 for a pair of used XA160.5's. (The combination of the XP25, XP30, and XA200.5 I heard at Marks' was outrageous - both in sound and $$, unfortunately).
If you want to read more, I have found two really good sources. The first is Nelson Pass, himself. Read his article Audio, Distortion, and Feedback on the Pass Labs website. In it, he discusses the various types of circuit design, distortion and the use of negative feedback. I found his observations to translate to what I heard in their X.5 and XA.5 amps. There are also interesting reviews of the XP20 and XP phono preamps on the hometheaterhifi.com website (the link can be found on the Pass website under Reviews.
Hope this helps.
My experience is deep, rather than broad, as I have not had the opportunity to compare Pass products to other gear. However, over the past 7 years Ive rolled a number of Pass Labs components through my system (mainly used and factory refurbished): X250, X250.5, X350.5, XA160.5, X-1, XP-20, Xono, and XP15. My speakers throughout the past 10 years have been the Martin Logan Odysseys.
As luck would have it, last summer I had the occasion to make a business trip to Nevada. I took advantage of the situation and spent an afternoon with Mark Sammut of Reno Hi-Fi, who graciously treated me to a comparison of various combinations of the X350.5, XA100.5, XA160.5, XA200.5, XP20, XP30, and XP25. Mark was running the Pass SR-2 speakers.
To my ears, anyway, Nelson and Wayne have been on a pretty consistent development trajectory. As you advance from the X-1 to the XP30, I would characterize the improvements as providing greater resolution (I think the same is also more or less true of the move from the X to X.5 class AB amps). By resolution, what I hear in moving up the Pass preamp food chain is a consistent increase in the black quietness from which the music emerges, an increasing ability to discern separate instruments and voices, better control of bass, and a wider and deeper soundstage. BUT, the magnitude of the differences I heard between these preamps depended on the power amp. The differences are more obvious (and breathtaking) as you move into the larger XA class A amps. IMHO, if you are running one of their class AB X.5 amps (or equivalent) the XP20 will be plenty of preamp. Yes, you will be able to hear improvements in the XP30, but put the extra $$ towards one of the XA power amp monoblock designs, instead.
I would characterize the improvements I hear in moving from the X350.5, to the XA100.5 and up the food chain to the XA200.5 amps as providing increasing amounts of body and 3 dimensionality to the instruments. To use a visual analogy, I would describe the X350.5 amp as providing a crystal-clear, hi-definition image. Using better and better preamps in the Pass lineup brings higher and higher definition, but turning up the volume simply makes that hi-def image brighter and brighter, and it remains, in essence, a 2 dimensional image. The XA amps take that hi-def image and turn the pinpoint voices and instruments into individual 3-D holograms of the real thing. The bigger the XA amp, the more palpable the holograms. With these amps, turning up the volume is like moving your seat in a concert hall closer to the stage. The soundstage reaches out and envelops you.
In my case, I felt that my system was better served by keeping my XP20, busting my budget, and trading in my X350.5 for a pair of used XA160.5's. (The combination of the XP25, XP30, and XA200.5 I heard at Marks' was outrageous - both in sound and $$, unfortunately).
If you want to read more, I have found two really good sources. The first is Nelson Pass, himself. Read his article Audio, Distortion, and Feedback on the Pass Labs website. In it, he discusses the various types of circuit design, distortion and the use of negative feedback. I found his observations to translate to what I heard in their X.5 and XA.5 amps. There are also interesting reviews of the XP20 and XP phono preamps on the hometheaterhifi.com website (the link can be found on the Pass website under Reviews.
Hope this helps.