sound quality of small amp vs big amp

jeff1956 -- Wed, 04/13/2011 - 16:26

I'm trying to understand the relationship between power and sound quality. My friend recently upgraded his McIntosh amp from 300w/ch to 450 w/ch. The old amp was dated 1998. He has B&W 803 speakers and a nice Mcintosh CD player. He plays music in his great room (no special accoustic treatments).
Anyway, on the new system he claims music is significantly better (clearity, separation,...) while @ a lower power level. On the old system he used play music @ 45 w (on mac power meter), new amp he plays same music @ 4.5 w. He's telling me it's mostly due to the new power supply has more power so the music is cleaner and fills the room so much better @ lower power. I'm struggling to grasp this concept.
To me it would seem like - for a given power level (4.5 w) the speakers would output the same volume level regardless of which amp he uses? I'm not sure why he thinks the new amp produces the same output (volume) @ 1/10 of the power output of the old?
Secondly I'm struggling to understand how the new amp can produce better music @ a lower power level. I can understand the music might sound better to him (maybe the electronics are better in the new amp or maybe he convinces himself it sounds better cause he just graded and needs to justify the expense). Considering that the Mcintosh brand is supposed to be of superior quality i can't believe the distortion would be that noticeable between the new vs. old amp (old amp16% of total power output vs 1% on the new).
Lastly - my local shop is always talking about some of the newer low power amps (>50 w) are so great you don't need high power anymore?

jeff1956 -- Wed, 04/13/2011 - 16:28

Mullard EL34 -- Thu, 04/14/2011 - 09:46

Jeff,
I've got to agree with your calling "BS" on the new amp delivering the same loudspeaker acoustical output with 1/10th of the power of the old amp; it's simply not possible. More than likely there is a difference in the calibration of the output meters. I know that McIntosh claims that their power meters actually take into account both the current and voltage delivered via the amplifier outputs, but the laws of physics don't permit a given loudspeaker to deliver the same level of acoustic output with a 10-to-1 variation in the loudspeaker input power. Also, the ballistic characteristics of the physical meters themselves must be matched; McIntosh meters do not adhere to professional VU meter ballistic specifications.

A simple test would be to feed in a steady-state test tone, measure the loudspeaker acoustic output level (Amazon offers a $50 handheld VU/decibel meter (http://www.amazon.com/Nady-10220-18-Analog-Spl-Meter/dp/B000A6V5FS/ref=s... ) and note the McIntosh power-meter reading. Hook-up the other McIntosh amplifier and adjust the input level until the speaker is delivering the same acoustic output level; then note the McIntosh power-meter reading. If both amplifiers don't display the same power-level reading, then something is wrong with the calibration of one (or both) power-meters.