Originally Posted by drh3b
Just a note on the Emotiva and the heatsinks. I have the XPA-3 Gen 3, and I play music super dangerously loud. It barely gets warm I mean, barely above room temperature, so the heatsinks are more than enough for the job. I guess if you get the 7 channel version, YMMV, but I've never seen anyone claim their Emotiva XPA Gen 3 amp gets hot.
Yes, I am not surprised. You can design amp with high power by low bias to keep it cool. That's what most of the cheaper power amps do. Crossover distortion is the major issue on the quality of sound. Whenever the amp crossover from the up half of the push pull output transistor to the lower half ( same as from lower to upper half), you get crossover distortion. The amount of distortion is the same amplitude. This means the effect is most dominant when the signal is small.
That's where class A amplifier comes in. Class A amp never switch from top to bottom ( bottom to top) half, both halves are always working, there is no crossover distortion. But you waste a lot of power running in class A.
That's where a kind of amp called HIGH BIAS class AB that run higher bias current. The higher the current, the more you push the crossover until the signal gets bigger. As said, crossover distortion is the same amount, so if the crossover distortion happens when the signal is larger, the less the effect on the sound. So the higher the bias, the less the effect of the crossover distortion.
Higher bias current means it still burn a lot of power and produce a lot of heat, that's when you need big heatsink. It has NOTHING to do with the max output power. You can have a 200W power amp that run very cold, and you can have a 50W amp that is high bias and run very hot. It's NOT the number of Watts that matter, it's the QUALITY of the watts that matter.
You can buy a 200W amp cheap and there are 50W amps that are very expensive, it all depends on what you are looking for. If you always blast the music, you actually don't need as good an amp as you always run signal much higher than the crossover distortion. You can get away with cheaper amps. But if you listen to the system soft, that's when you need good quality amplifier.
It is my experience that a lot of amps sound good play loud, ONLY the really good amps sound good playing at low volume.
Like the amps I design, they are only about [email protected]
, but [email protected]
and [email protected]
Even with huge heat sink, because I run at 1A bias current, it gets really hot even at this low power. Because of the limit of the heatsink size of the chassis, I can only get [email protected]
My bigger amp is [email protected]
, it's 8" tall, that's very big for only 100W. It still running very hot.
You can buy a cheap Yamaha AVR with say 5 channel, 200W each, all in one chassis, weight less than 30lbs and run cool. Do I need to comment on the sound?