Alan8947
Full Member level 4
It's not about power handling, it's about lowering distortion and maintain high bias current. The main distortion of power amp is crossover distortion where the drive change hands from one to the other transistor in the pair( class B). This distortion does NOT depend on the signal amplitude, it is constant amount. This means the lower the signal level, the more obvious the distortion. This crossover distortion affect the sound quality at lower listening level rather than at loud volume. In another words, at high volume, the crossover distortion becomes so small compare to the signal that it's not important.
The ways to lower crossover distortion is to have more pairs of output transistors. The distortion lower by almost half when you double the number of pairs of output transistors. Using more pairs IS the key of lowering crossover distortion.....that make the amp sounds good at lower volume.....which is the key of an audiophile amp.
The other way to avoid crossover distortion is to have higher bias to create a bigger class A region, so in small signal, the amp is operating in class A. I run 0.9A ( 100mA per output pair) to get about 8W of class A with 4ohm or 16W with 8ohm load. With home listening level, you literally have a class A amp. The rest of the power is for head room during fast transient. That's why if you look at the high end amps like Krell, Threshold, they use a lot of pairs of output transistors. It's not for show. I use the Nakamichi PA-7 Stasis amp designed by Nelson Pass for comparing with my amp. PA-7 is almost the same circuit as the Threshold S300. It is very obvious that at lower volume, my amp has more separation, clarity, sound stage than the PA-7. I believe it's because my amp has over double the bias current of the PA-7.
For DJ, you need none of these. Design is a lot easier, you don't need to have that many pairs of transistors. More importantly, you don't want to carry my amp around. It's over 50lbs!!!! You want something that is lighter. A lot of DJ uses class D amp as sound quality for DJ is not that important.
The ways to lower crossover distortion is to have more pairs of output transistors. The distortion lower by almost half when you double the number of pairs of output transistors. Using more pairs IS the key of lowering crossover distortion.....that make the amp sounds good at lower volume.....which is the key of an audiophile amp.
The other way to avoid crossover distortion is to have higher bias to create a bigger class A region, so in small signal, the amp is operating in class A. I run 0.9A ( 100mA per output pair) to get about 8W of class A with 4ohm or 16W with 8ohm load. With home listening level, you literally have a class A amp. The rest of the power is for head room during fast transient. That's why if you look at the high end amps like Krell, Threshold, they use a lot of pairs of output transistors. It's not for show. I use the Nakamichi PA-7 Stasis amp designed by Nelson Pass for comparing with my amp. PA-7 is almost the same circuit as the Threshold S300. It is very obvious that at lower volume, my amp has more separation, clarity, sound stage than the PA-7. I believe it's because my amp has over double the bias current of the PA-7.
For DJ, you need none of these. Design is a lot easier, you don't need to have that many pairs of transistors. More importantly, you don't want to carry my amp around. It's over 50lbs!!!! You want something that is lighter. A lot of DJ uses class D amp as sound quality for DJ is not that important.