This is terribly unscientific, so don’t shoot me, but it’s my experience. Based on how well it measured, I recently bought a Denon avc-x3700h to accompany a new tv in the second lounge. I already have a Denon avr-x7200wa for the main lounge. The x3700 weighs 12.5kg, the x7200 17.8kg and the difference in sound quality for stereo music broadly reflects the relative weights with the same Revel f206s front speakers and the same SMSL SU-8s in each room! I exchanged the x3700 for an ex display Yamaha RX-A3080 which weighs 19.6kg and again, the sound quality reflects its weight.
Much the same measure of the size of the power transformer in an A/B amp is the maximum power consumption: the x3700 is 660 watts, the x7200 is 780 watts and the Yamaha RX-A3080 is 1210 watts, again a pretty good reflection of the relative sound quality.
The NAD T777 weighs 20.5 kg, so it’s a no brainer: if Sevenoaks at Bromley have still got it, buy it ‘cos it’s an absolute bargain! It will sound far better than the Denon avc-3700h. Or buy the ex display Yamaha RX-A3060 they’ve got at their Maidstone branch.
Not necessarily! Power consumption figures are not always a reliable indicator of transformer size (VA) because manufacturers don't follow the same rules/standards for the power consumption specifications. The power output specs are actually more reliable because most at least follow some sort of rules and standards such as FTC., though they don't seem to want to disclose exactly which one the follow.
Electronic Code of Federal Regulations (eCFR)
It is sad that, there don't seem to be stricter rules/standards enforced/regulated to product audio hobbyist/enthusiasts. Thanks to sites such as ASR, at least we can rely to a large extent on bench measurements.
Take a look of the Yamaha 3080's specs on weight and power consumption:
RX-A3080/RX-A2080 Owner's Manual (yamaha.com)
•
Power Consumption.........................................................................................................................................................................................
490 W
•
Maximum Power Consumption [Brazil, Asia, Taiwan, Central and South America and General models]........................
1210 W
So if you just read "Power Consumption, it is 490 W
Now look at the weight specs:
• Weight [RX-A3080] [China, Australia, U.K., Europe, Middle East and Russia models] ............................................................................... 19.6 kg (43.2 lbs)
[Other models]...................................................... 18.1 kg (39.9 lbs)
Denon/Marantz do not specify "Maximum" power consumption, just " Power consumption"
So you can't compare the spec between the two brands unless you know the specific rules/standards they follow.
As for weight, Yamaha has a larger enclosure and that could be one reason why in general they seem to run cooler.
Denon/Marantz's design allow their units to run warmer, apparently rely more on the temperature controlled fans, and probably use more plastic, so they are lighter not necessarily because they use lower VA transformers, could even be larger in VA while lighter in weight depending on their custom design/build specs. Note that the NA (such as US, Canada) Yamaha RX-A3080 are 3.3 lbs lighter, that may have something to do with the lower power supply voltage, 110/120 V vs 220/240 V but there could be other reasons too, that likely don't affect "sound quality".
NAD's are generally heavier, but if you look at their bench tests (that don't lie), their measured output on the bench have been consistently lower than Denon/Marantz and Yamaha's, even under 5, 7 channel driven conditions, 8 or 4 Ohms. So going by just weight and power consumption may be fine and "scientific" if you are comparing models of within the same brand and model year, but clearly not if you are comparing units across different brands/model/model years.
Anyway, it is not uncommon people hear "better sound" from heavier, pricier or even better looking (to them) products because they expected it..
