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Originally Posted by thezaks
How did the comparison go?
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Thanks for the reminder. I’ve been enjoying the X260.8s so much it slipped my mind I owed a post or two about the new amps. The short version is, I updated my AA signature when I sent the X250.8 back to Mark Sammut at Reno HiFi. Definitely keepers.
Mark advised a good five days of 24/7 operation before doing any critical evaluation of the new amps, and based on what I heard when I started peeking two days in, he was right. At first I didn’t like them nearly as much as my well broken-in X250.8. They sounded forward, flat and peaky. Very dynamic, but very fatiguing. My first impulse when listening was to turn them down a good 3 to 6 dB from where I normally listen with the X250.8.
Thankfully, they started mellowing a bit by the third and fourth evenings. By the time I had the recommended minimum hours running in, they had settled down quite nicely. However, some 300 hours into running them 24/7 they still sound like they are slowly breaking in — that is, they keep getting better and better.
What do I hear as the differences between the X250.8 and X260.8s?
The X250.8 is a bit more laid back and relaxed in comparison to the mono blocks. It wouldn’t be too much of a stretch to call the X250.8 almost liquid — though not languid — in comparison. The X260.8s are more vivid and feature more transient jump. My startle reflex engages more with the monos. The 260.8s also possess more separation and depth and a more 3D quality compared to the stereo amp, and I thought the X250.8 was quite good in these areas.
I also hear a bit more detail and texture as well as image specificity with the mono twins. There is a little more rosin on the bow, without losing any essential body and weight. Soundstage is deeper and the front edge has shifted bit more forward than the X250.8, but it’s far from being in my lap. In combination these differences add up to a performance improvement that sounds quite significant and attractive to my ears.
Attributing these differences solely or even mainly as a result of the X260.8s staying in Class A longer than the X250.8 is probably not completely accurate. Nelson Pass has stated that one of the biggest differences across the entire .8 line from the prior .5 amplifiers was his decision to tailor the input and driver stages specifically to each power stage, where the earlier models basically shared the same front end and only varied power supplies, heat sinking and numbers of output devices to accommodate different levels of power output. I suspect this same customization of front ends holds true between X250.8 and X260.8s, particularly since there is a significant bias increase for the mono blocks. Since I’ve yet to see any meter needle movement that would indicate more than a transient departure from class A operation with the X350.5, X250.8 or X260.8s I’ve spent time with, I don’t think staying in class A longer tells the whole story.
I can’t discount two very large power supplies, as well as having everything else isolated on two chassis, along with bias and topology differences having their audible effects. Whatever the secret sauce might actually be, the X260.8 amplifiers are very impressive.
And none of the above takes anything away from the X250.8 which might just be the sweet spot of Pass’ line of single-chassis stereo amplifiers.
The X260.8s perfectly hit the mark with my KEF Blade 2s and what I like my particular fi to sound like. Mark suggested the XA series are even more vivid and up-front and might be a bit too much of a good thing for my listening preferences and speaker choice. So far he’s batting 1.000 so who am I to doubt?
I couldn’t be happier with the X260.8s and in fact, I’m heading downstairs in just a bit for another evening listening to music. If it goes the way it has been since the new amps arrived, it will be the early hours of the morning before I wrap it up.
Which is what it’s all about, isn’t it?
Steve Z