How much amplifier power do you really need?

[David A]

… If it is determined that someone needs a D1000 because a D140 distorts or goes into clipping or the protection circuits trigger frequently then by all means use the bigger amp.  On the other hand, if a D140 can satisfy every criteria the listener needs using a D1000 in place of that WILL NOT make the system sound better.  That's the point.

2 amps can satisfy the same criterion but one can exceed the other in the extent to which it satisfies that criterion. The fact that both satisfy the criterion doesn't mean that they will perform equally well in satisfying it. Lets say you only need 100 watts/channel into 4 ohms. An amp specified to deliver 140 watts and one that specified to deliver 200 watts both satisfy the criteria but measurement procedures for testing specifications are standardised and a standard test load will be used to confirm the specification. Speakers aren't standard test loads and one amp may be capable of handling the load a given speaker presents better than the other. The amp that handles the given speaker better may be the smaller amp or it may be the larger but whichever one handles the load better will perform better with that speaker. The fact that both meet the specification doesn't mean that both will perform indistinguishably with the same speaker.

What do I mean by all else being equal?... well... by all else being equal!  Joking aside, lets assume the only two differences in a given room and system were the D140 and the D1000.  If the D140 was pushed beyond it's capabilities, lets say to an SPL of about 102dB (my setup) then the extra headroom (8.54dB) provided by the D1000 could make it sound better than the D140 but only because the D140 is underperforming, not because the D1000 is not underperforming.

Power, in and of itself, does not determine sound quality.  It's the engineering that goes into making power that determines sound quality.  Architecturally speaking, the Expert Pros are identical and so they should sound the same for a given SPL that does not breach the capabilities the weakest amplifier, the D140 in this case.  I say "should sound" because people have varying opinions about what they hear.  But what they hear has no baring on what is, the Expert Pros are in fact the same.

Any differences that exists between the models (besides the additional power) has to do with how efficient each model tackles the additonal heat that is generated.  The D1000 can produce more heat than the others and therefore steps were taken to make it dissipate heat better allowing it to be a true dual-mono design.  The other models like the 440 and 210 are "dual-mono" in nomenclature only and are not true dual-mono capable.  If they were then the power output of each would QUADRUPLE, not be limited to double more power you get with the D440 and only one and a half times more power you get with the D210. But let me be clear, the D440 and the D210 are true dual-mono designs but Devialet limits their capability because of the additional costs it would incur to deal with the additional heat.  This in turn helps lower per unit costs making it possible for Devialet to sell to a larger audience.  Remember, this is a business... first, and power is expensive but sound quality needn't be.  Want proof?  The DAC shootout I briefly mentioned in another post was very telling.  The cheapest DAC won!

I remember seeing somewhere the specs for the power supplies of the different models and there are differences in the size of the power supplies. My understanding is that the 140 can only deliver 50% more power in a dual amp setup because it is current limited, and the 220 only delivers twice the power in a dual setup because it is limited by it's ability to dissipate heat. The 250 can deliver 4 times the power in a dual setup because it suffers from neither of those limitations. The architecture of the power supply in each case may be identical, the capacity of the power supply in each amp is not identical. It is not the case that the 3 amps are identical in every performance respect apart from power output.

As I said, the specifications tell you about what was measured and not everything relevant to the amp's performance gets measured or included in the specification sheet. The specifications tell you nothing about performance parameters that were neither specified or measured. No manufacturer provides specifications for how well an amplifier deals with the non-standard load presented by every speaker, they provide a specification based on a standard load and the only way to find out how it will work with your speakers is to hook them up and listen.

The day when we can dispense with the need to listen and know everything about how a speaker will perform with a given speaker under real life conditions are still a long way away. Until that day people will be reporting differences in sound quality between amps which are capable of delivering enough power for their needs and there are reasons for the differences they hear which have nothing to do with one amp having more or less power output than the other. If there is a difference in power output then there will almost certainly be other differences as well. All other things besides power output are never equal in real life, even with amps in the same range such as the Expert Pro models.