Chip amps are interesting. Much of their sound quality depends on the power supply, and the filtering system that comes after the output devices. There is a filter system that needs to deal with the switching distortion created by the output devices. How intrusive that is, effects the final sound of the amplifier.
A majority of the cost of a good amplifier is located in the power supply. The inexpensive chip amps will use a basic switching power supply that is typically known to be noisy. The higher quality Class D amps will use a conventional power supply like the one shown in the Audio Research chip amplifier above, and a power supply like that costs real money. Also the chassis of that amplifier is expensive, and adds to the price tag. But a conventional power supply needs room to be laid out, and so larger chassis are needed. There are companies building higher quality switching power supplies, but they are not dirt cheap.
Some folks here think that the commercial or pro audio Class D amps are the proper implementation of the design, and have a price structure that is reasonable. Crown makes amps that meet this criteria for instance, and are probably a better example of the technology than the Lepai. In the realm of boutique hif fi, an amplifier like the D Sonic or Wyred4Sound are examples of what is possible if you spend more money.
The one thing about inexpensive Class D amplifiers is that the chips are current limiting. They put out their max power at a 4 ohm rating, and less power into 8 ohms, so for many home speakers they are not as much power as you expect them to be, as many home speakers are an 8 ohm load. But when you drop below 4 ohms you are hard on the circuit because the output chips and power supply are not spec'd to pass that much current or the chips are not heat sinked well enough to dissipate additional heat, at least in the cheaper amps like the Lepai. The better ones can do it within reason, but they still won't drive the wicked low impedance loads of some speakers. However, in todays audio world speakers do not have the nasty low impedance dips or phase shifts in their crossover that taxed the affordable "high power" amps of the 80's ans 90's.
Class D can only improve in sound, and it has from its inception. There are excellent Class D amps on the market now. But they aren't the ones that cost $50. Although there is a group of hobbyists out there that have reportedly gotten great sound with a little DIY project based on the TPA3116 board and high efficiency speakers. So there are no absolutes about how much money has to be spent, or what the cut off point is for good Class D amplification. It is like anything in audio, do your homework, understand what your preferences and priorities are, find a candidate and spend your money and takes your chances. Audio is a journey!
Regards
Mister Pig
