- Bigger is better. While small low wattage amps have some appeal to a small group of Audiophiles, the majority of music lovers will benefit from having a high wattage power amp to make sure there's plenty of headroom so the music is never compressed sounding and always effortless. It is this lack of tension and compression that helps us listen to music as if it were live.
- The gain of the amp shouldn't be related to its power. A common misconception is that when an amplifier gets bigger or smaller in its power rating that the amp's sensitivity or gain is affected. Generally this is not true and a high power amplifier will output the same volume level for a given input as will a smaller power amp.
- Bi Amping requires identical gains. If your loudspeaker can be biamplified, meaning there are two sets of input binding posts - one set driving the upper midrange and treble, the other driving the woofer - you have to make sure the two amplifier you use have exactly the same gain.
- Output transformers affect the sound. Most tube power amplifiers, certainly most SET's, have an output transformer to match impedances. This transformer cannot handle the varying load impedances most loudspeakers present and thus the tonal balance of the presentation will be changed in a manner that is not true to the original recording.
- The input stage of a power amplifier has a great impact on the sound. Amps are divided into two areas: the input voltage gain stage (or the comparator in a Class D) and the output power stage. By far the greatest impact on the sound quality of an amplifier can be found in the first input voltage gain stage or comparator stage.
- Class D amplifiers are closely related to DSD. DSD uses PDM and Class D amplifiers use PWM but share something in common: their direct coded output is analog-like enough that you can play them directly into a speaker or preamplifier and get music. This is not true in a PCM based digital audio approach.
- XLR balanced connectors are the way to go. If you can always use the balanced XLR connectors to connect together your preamplifier/DAC to your power amplifier. Properly designed, this type of input can provide up to 70dB of noise and distortion rejection.
Putting it all together
I think we've probably spent enough time on amps for a little while - we can always return - so I'd like to sum up some of our findings and then move on to our next topic tomorrow. Here's a list of some of the topics we covered:
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