Originally Posted by PlasmaPZ80U
Yamaha AVRs in particular or all AVRs?
In any case, I think you're right because it sounds a bit dull even at low volume and the claimed 20% power savings doesn't seem like much.
I still haven't found any "real" information about how Yamahas ECO mode works, it seems to be different to "other" (e.g. Denon/Marantz).
D&M's Eco=auto mode is really clever!
a little bit background: a typical class A/B amp needs some idle current. That means this current flows through the transistors even without any signal (mute).
for amps with just one pair of transistors per channel the idle current is typically between 50 to 100mA.
on the other hand the wanted output power dictates the rail voltages because thats the maximum output voltage peak to peak (minus some loss). For 150W at 8Ohm 100V (+/-50V) are required, you definitely can't reach this output power with less voltage.
that means: each channel of a 150W amp converts between 5 and 10W electrical energy to heat without a signal, doing nothing!
7 channels -> 35 ... 70W heat without a signal
the trick is to reduce the rail voltage when it is not needed!
if you turn the volume to -10dB it means 1/10 of the maximum power, the 150W are reduced to 15W and a little bit more than 30V are sufficient.
and what's really convenient: there is a reduced voltage setting available already: for the 4Ohm modus!
so if we reduce the voltage to 50V (40W/8Ohm, 80W/4Ohm) that's still sufficient for -6dB volume level!) we reduce the dissipation loss to half (18...35W for 7 channels).
so what D&M in Eco=auto does is the following:
as long as the Volume is below -30dB (1/1000 of the maximum power) the voltage is kept at the reduced level
if the volume is above -30dB and there is a signal the voltage is switched to "maximum power"
the voltage stays at max power mode until the volume is turned down below -35dB
it's pretty easy, doesn't cost any power or sound quality and reduces the power dissipation / heat. There is no reason why you shouldn't use the Eco=auto mode for a D&M AVR.
now I still need to know how the Yamaha system works