Upgrade from Pass Labs XA30.8 to X250.8. Worth it?
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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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. |
@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! |
Greg, thanks for the comparison. Exactly on point. I just wonder how many people make the switch after hearing them side by side? George, I did some research a while back on the DM947’s. I tracked down what I believe is the actual driver for the speaker. It’s called the “Silver Flute.” The drivers themselves appear to be relatively inexpensive (hence not highly advertised), but they do sound a lot better than the parts price suggests. They do have the benefits of a crossoverless wide-bander. You can find them here: https://www.madisoundspeakerstore.com/approx-8-woofers/silver-flute-w20rc38-04-ohm-8-wool-cone/#prod... |
A few months ago I listened to both (250 & 30.8) and some other amps driving a pair of Danish, not very sensitive, spkrs. Between the two, the 250.8 had much more driving authority but the 30.8 won on timbre and sound quality overall. If I remember correctly, your Decwares are xoverless and very sensitive, so I cannot say if the added power will give you what you are looking for since the 30.8 by itself should be powerful enough to drive them well. Perhaps repositioning your spkrs could help? Then again, one can never have too much power, can one:) |
