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Upgrade from Pass Labs XA30.8 to X250.8. Worth it?

I am getting ready to make some upgrades to the system. I currently running a DAC into a BAT51SE, then a Pass Labs XA30.8, then finally into Decware DM947 speakers (don't worry if you've never heard of them; not the last word in speakers, but have been doing a solid job for about 5 years now.)

I am contemplating moving up the Pass Labs amplifier line, and the X250.8 looks attractive. I would like to hear more bass authority and definition, but I don't really want to sacrifice the mids and highs of the 30.8. 

I would love to hear some of your impressions of the X250.8, especially if you are able to make some direct comparisons to the XA30.8. I've spoken with both Mark at Reno Hifi, and Kent English of Pass Labs; both are wonderful and informative people. What I am interested in now is the opinions and experiences of end users of either of these amps. 

Thanks! 
willrich47
willrich47 OP
52 posts
 
@twoleftears I was once intrigued about that particular amplifier. I asked Mark at Reno Hifi about it, and he indicated that the 30.8 does just about everything better than the XA25. Though admittedly, I haven't compared the two. I did own the 30.5 before the 30.8, and could compare those two if you'd like! 

@jafant I was fortunate to find a copy of my B.A.T. on Audiogon. It had been recently recapped and was in great condition. I came from a tube amplifier. The B.A.T. has a slightly warm and dark sound to it, which I really like. I am always striving for simplicity in my system, and I have taken it out a few times to decide whether I could "live without" it. As soon as I remove it from the audio chain, I immediately miss it. I am definitely a proponent of having tubes SOMEWHERE in your audio chain. Love that sound!

@hk_fan Thanks for the response. This is why I posted here. To get a wide variety of opinions on the topic, even if they are conflicting. I am a bit confused though because Mark seems to think that the X250.8 is a solid upgrade from the XA30.8. Kent seems to like the X250.8 very much too (claiming to keep that one at home a majority of the time) but admits that it isn't as warm as the 30.8. I'm hoping to find some of those "happy customers" Mark was referring to; or even some unhappy ones. 

@snopro the sentiment is not lost on me. I am still trying to wrap my mind around why bigger AB amps often times have better bass, even though the output may be the same as a class A amp. Even more within the Pass line. Moreover, why does 1 Class A watt from the X250.8 sound different from 1 watt from the XA30.8. No idea, but trying to learn! 

Thanks all for the responses so far!
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hk_fan
462 posts
 
The X250.8 may have better bass, but bass is easy - the liquidity and smoothness of the XA in the mids and highs is what's difficult.  If you want bass, keep the the XA and buy a quality powered sub.  Completely serious here.
auxinput
2,920 posts
 

I am still trying to wrap my mind around why bigger AB amps often times have better bass, even though the output may be the same as a class A amp.


What is most likely happening here is that the fully Class A amps require so much constant DC that the power supply just doesn't have enough on tap for the powerful bass hits.  It requires an enormous amount of power supply capacitance to supply enough "smooth DC" power for that constant 30 watt Class A sink -- that it's only just enough to carry through for normal music.  When bass frequencies hit, it will pull even more on the power supply, which is just treading water enough to keep the voltage up (though I suspect voltage will dip anyways on the high power bass hits).  I suppose the exception would be very huge amp, such as the XA200 monoblocks, or something like a Krell FPB300+ monoblocks.

On a large Class AB amp, such as X250.8, the power supply is sized larger than the XA30 with a larger transformer as well so that it can sustain that 250 watts per channel.  However, you hardly use much of that, probably 5-10 watts constant draw during normal music and when the bass hits, the power supply transformer and capacitance has enough current on tap to push that bass frequency waveform through the speaker before it needs to draw on the main A/C current to recharge the power supply caps.  The power supply is able to draw A/C voltage at 60 hz, which is generally fast enough to keep the power supply full for low bass frequencies.

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auxinput
2,920 posts
 

kosst, honestly, I really don't trust anything you say anymore.  Now if almarg came in and corrected me, I would believe him.

I do know that Class A amps have a much larger constant A/C draw.  In Class AB an amp might have an idle current of 63 watts, but if biased to something like 30 Watts Class A, the constant "idle" A/C draw may go up to something like 160-170 watts.

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