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Pass XA Monoblock Amps

I know there have been many threads on these amps and the different levels of power with each set. To those who owned the Pass XA60.5 and went to the Pass XA100.5 monoblocks, did you feel that the change made a big difference in your system or was it not that noticeable whether played at low to mid level volume levels or high volume. I currently own the Pass 60.5 and am contemplating the Pass 100.5. Some people have suggested that it would take a move to the Pass XA160.5 for it to really make a difference but that would unfortunately be out of my price range. The room is 12 by 24 and the speaker load is 2 ten inch seas woofers, 2 seven inch mids, and the tweeter. They are 4 ohm with a sensitivity of 91 but a big speaker. Any thoughts from Pass owners of these amps would be appreciated. The other direction i can go would be to upgrade my Pre-amp from the Rowland Capri but my initial thought was that the Pass amp change would be more of an upgrade. Thanks for your thoughts.
pettyfeversk
pettyfeversk OP
87 posts
 
Hi Charles,

Thanks for responding. The XA.5 series has a very strong class A power supply but if you have the volume up to a high level, you reach a point where they transition from pure class A to classA/B. That happens with all the amps in the XA series and definitely happens to me with my speakers which can take a good amount of power. You can see the bias need move as you go up the volume level and they move to AB.
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almarg
9,670 posts
 
A point that might be relevant is that speaker sensitivity is often defined with respect to 2.83 volts, rather than 1 watt. For an 8 ohm speaker that would make no difference, since 2.83 volts into 8 ohms corresponds to 1 watt. But 2.83 volts into 4 ohms corresponds to 2 watts, so if the 91db figure of your 4 ohm speakers is defined with respect to 2.83 volts, they would be 88db/1W/1m speakers, not 91db/1W/1m.

I did a quick Google search, but couldn't determine how the 91db is defined.

Beautiful system and setup, btw.

Regards,
-- Al
rtilden
156 posts
 
Bingo, Almarg!
I have recently moved from Tyler's Woodmere 2 to the new-style full-sized Woodmeres, and I am getting to know the speakers pretty well now. Tyler had told me that the Woodmeres are 90db, calculated theoretically based upon the crossover/driver combination. Their load drops to just above 2 ohms at worst case, according to Tyler. I suspect that if they were measured in a lab, the 88db figure would be about right. These larger speakers require a pretty good bit of power (and I think current also) to make them sing. They sound very nice and relaxed at low volumes, but they do like the juice.
inna
7,789 posts
 
Al, I wonder how those bloody Cardas cables contribute to the overall sound from the perspective you mentioned?
Rocket science, anyone?
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almarg
9,670 posts
 
Inna, I have no particular familiarity with the Cardas GR's, but from a specification standpoint, at least, I don't see any concerns. Resistance and inductance are extremely low. Capacitance is a little bit on the high side, but I would feel certain that it is not anywhere close to being high enough to cause sonic issues with a Pass amp (conceivably it might be if used with an amp that uses lots of feedback and has extremely wide bandwidth; the Pass amps do not have either of those characteristics).

Rtilden, thanks for providing the good info.

Regards,
-- Al
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