Just a short pick up for the balance headphone amps.
1, Less distortion : The balance amp built with two amps for the hot and cold signal in each channel, the cold and hot signal will meeting at the headphone, so can counteract most distortion .
2, Higher S/N : The philosophy as the point 1, the balance amp not only counteract distortion but also counteract the noise from transmit between source and amp and the amps inborn noise . So balance amp not only have advantage in long distance transmit but short distance transmit for less noise .
3, Higher Slew rate Etc : If a single ended amp have 100V/us slew rate, a balance amp based on this single end amp can arrive 200V/us . The faster Slew rate can keep the signal output more follow the input signal , thus have more neutral and monitor sound, easy arrive "the wire with gain" .
4, Less request from power supply : Even the power supply undulate but the balance amps based on the difference can avoid the effect .
5, Higher power output : In theory is 4 times .
6, Less effect by the parts model : Keep the balance amps have same parameter parts can easy arrive the design target .
1, Higher cost : Four amps for the stereo headphone amp, compare to two amps in the single ended amp , usually have near double cost . And request the parts parameter exact match in the hot and cold amp cause the building cost higher.
2, Larger size : Usually have near double size .
3, Higher output impedance : Usually have double output impedance . For a Monstor power amp, lower the output impedance to 50% is much difficult but for a headphone amp, lower the output impedance to 50% just easy, maybe without any cost increase .
Thanks Kingwa for the technical explanation. Looks like I have to buy Norse Balance cable for my LCD-2
As for the weakness #2. I heard that the 'exact match'nes will drift over time? that will cause unevenness on the sound?