Quote:

Quote:

Here is how Peter Aczel states it: "It is impossible for two amplifiers to sound different at matched levels if each has high input impedance, low output impedance, flat frequency response, low distortion, low noise floor, and is not clipped." Amen.

Regards,



So Alan, are these characteristics normally found in low end receivers typically found sitting on the shelf at Wal-Mart?



I don't know, since, as an audio-video hi-fi magazine editor for many years, I never reviewed or bench-tested really "low-end" electronics. I'd have to get hold of one that we'd agree was "low end" (Chess is correct: How do you define that? By price alone? Not a good indicator. .), run power bandwidth, frequency response curves, a THD + Noise measurement at various impedances and power levels, and put a spectrum analyzer on it while measuring Intermodulation Distortion (IM).

If the low-end receiver passed all those tests--some of which are quite rigorous, in particular the IM test--with good results, then if you set it up opposite a different AV receiver (assume a more costly model if you like), equalized the SPL output to within a 1/4 dB or less, made sure you didn't drive either amplifier into clipping by monitoring the audio waveform with an oscilloscope, and put it on an AB comparator concealing the price, brand and size of each product, then yes, there would be no difference in sound quality provided both units meet the aforementioned criteria.

It would be an interesting test. Clearly there are all kinds of electronic compromises made in the design of some electronics to meet very low price requirements--cheap IC output sections for example--but such shortcomings would normally show up in the lab bench tests as high distortion of one type or the other. Based on previous studies of the audibility of distortion (and on my own experience), and the measured distortion levels, I might be able to predict whether they would be audible with music or soundtracks. If, for example, there were measured levels of THD or IM distortion that were 40 dB down--that's equivalent to 1% distortion--or higher, then those might well be audible in an A/B comparison.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)