Pass labs xa25 amp and BW 804 d3?

@jetter, like many of us I wouldn’t consider my range of experiences to be extensive enough to put it quite as broadly as you did in your question. But I would certainly consider the XA25 to be a very strong candidate that should be considered by anyone looking to purchase a solid state amp in its price range or higher, for use with speakers having medium to high sensitivities.

Also, thanks to the others who have recounted their experiences and provided additional perspectives on this very special amp in recent posts. Enjoy!

Best regards
-- Al

A minor point but one that should probably be mentioned is that the Vandersteen 5 has a built-in amplifier handling the deep bass. And it is designed to be used with a passive high pass filter inserted between the preamp and the power amp, which rolls off low frequencies by 3 db at 100 Hz and at 6 db/octave below that frequency. (The built-in sub amp provides a complementary frequency response which restores overall flatness). So the power that is demanded of Macguy’s X250 is significantly reduced relative to what be required if it were driving a comparably efficient speaker full range.

In any event, it appears that the Vandersteen 5, like the currently produced 5a Carbon, is rated at 87 db/2.83 volts/1 meter, but apparently has an 8 ohm nominal impedance rather than the 5a Carbon’s 6 ohms. Assuming those specs are accurate it can be calculated that at a typical listening distance of say 10 feet, and in a medium sized room, two such speakers will produce an SPL for a centered listener that is in the vicinity of 95 db when both are driven with 20 watts. Enough for many listeners on most or all of their recordings, but certainly not enough for some listeners, especially on recordings having wide dynamic range.

I do not agree with the popular audiophile axioms, "the more power the better" or "enough power is never enough".

I disagree with those axioms as well, Charles. A point that seems to often be overlooked by proponents of those axioms is that for a given level of amplifier quality more watts usually = more $, at least within a given amplifier topology and a given class of operation (A, AB, D, etc.). So if a given amount of money is to be invested in an amplifier of a given topology and class of operation, choosing an amp that has more power capability than necessary may very well mean that more of those dollars than necessary will be directed toward watts rather than toward quality. At least that’s how I see it.

Best regards,
-- Al

@Cal3713, I’ve sold the VAC Renaissance 70/70 MkIII amplifier and I’m using the XA25 exclusively. I decided to purchase the XA25 a few months ago while the VAC was back at the factory for a minor repair, motivated mainly by all of the glowing reviews I’ve seen of the XA25. While also taking into account the sterling reputations of Pass Labs and the dealer from whom I purchased the amp (Reno HiFi) for customer service and support, as well as Pass Labs’ reputation for building products that tend to be reliable and trouble-free over the long-term. Regarding the reviews, I found Teajay’s (Terry London’s) review to be especially accurate in its characterization of the amp’s sonics, at least with my easy to drive Daedalus Ulysses speakers.

Following are some comments about the XA25 that I had occasion to post a few months ago in a thread that was mainly on a different subject:

It comes amazingly close to the VAC with respect to dimensionality, imaging, liquidity, and other traditional fortes of high quality tube amps. It’s a bit less rich sounding than the VAC, but I interpret that as an increase in accuracy, which is fine as far as I am concerned.

There are also some non-sonic factors favoring the XA25, including the likelihood of greater reliability in the years ahead considering the age of the VAC; the fact that even though both amps operate in class A the XA25 puts only 240 watts of heat into the room compared to what I believe is upwards of 700 watts for the VAC; and the cost that would be involved in re-tubing eight 300Bs if and when that were to become necessary.

This is the first time I’ve had a high quality solid state amp in my system in about 25 years, and I believe I’ve picked the right time and the right model with which to do so again.

On another note, happy holidays to you and yours, and all best wishes for 2019!

-- Al

Thanks for your very informative posts, Kosst. I’ve learned some things from them about my own XA25 that I didn’t know previously.

Regarding the references in one of your posts to "average volume," others should keep in mind that what matters with respect to an amp’s maximum power capability is of course the maximum volume levels that are reached on the recordings that are listened to, not the average level. And the relation between the maximum and average volume levels will vary dramatically among different recordings, depending on both the music and on how much dynamic compression has been applied in their engineering.

For example, some classical orchestral recordings that have been engineered with minimal or no dynamic compression may reach brief dynamic peaks that are 30 db or more greater than the average level of the recording. Which in turn means that around 1,000 times as much power will be required to reproduce those brief peaks compared with the amount of power required to reproduce the average level of the recording. While many and perhaps the majority of pop and rock recordings are compressed to a dynamic range of less than 10 db, which will require less than 10 times as much power for peaks than for the average level.

Thanks again. Best regards,
-- Al

While the XA25 is rated at 25 watts into 8 ohms and 50 watts into 4 ohms, John Atkinson's measurements that were reported in Stereophile indicated that it is capable of providing 80 and 130 watts into those impedances, respectively.  A lot of that disparity is apparently due to the Pass specs being based on distortion percentages that are extremely tight and are much lower than the ones JA bases his results on, and presumably some of that difference reflects the amp's capability after entering class AB mode rather than class A.

The speakers are rated at 89 db/2.83 volts/1 meter, with impedances of 8 ohms nominal and 3 ohms minimum.

FWIW, my XA25 has no trouble cleanly generating 105 db peaks at my 12 foot listening distance, with 6 ohm speakers rated at 97.5 db/1 watt/1 meter.  However 89 db speakers will require approximately seven times as much power as 97.5 db speakers to generate a given volume.

My guess as to the bottom line is that the answer will depend on the dynamic range of the recordings you listen to, with classical symphonic recordings that have been engineered with minimal or no dynamic compression being among the most challenging kinds of recordings in that respect, as well as your preferred listening volume, room size, and listening distance.

Regards,
-- Al