This is a review and detailed measurements of the Emotiva BasX series A-500 five channel home theater amplifier. It is on kind loan from a member. The A-500 costs US $529 which seems reasonable given the functionality and ratings.I can't say that I find the A-500 attractive but is not ugly either:Here is the connectivity which sadly does not include balanced XLR connections:This is a Class AB amplifier with a rather larger toroidal transformer. It is not overly heavy though which my back appreciated.The heatsinks end well below the top of the case so it was hard to judge how warm it got by touching the case. A quick test with IR temperature sensor showed the heatsinks running around 50 degrees C.In use the A-500 never complained, shut down or go into thermal protection. This is nice benefit over the delicate amplifiers in AVRs which if you look at them wrong, they go into protection/shut down. Clearly this is much more robust solution.As usual, we start with our dashboard of 1 kHz tone into 4 ohm load at 5 watts output:I was surprised by two things: large channel disparity with respect to distortion (SINAD) and very high mains hum at 60 Hz. No amount of playing with grounding fixed the latter which tells me the 60 Hz is probably induced from the transformer into the amplifier section. The former, channel distortion parity varied with which channel you used. Channels 1, 2 and 4 were very close and good. Channels 3 and 5 lagged way behind.The "good channels" had their SINAD actually dominated by that mains hum and power supply noise, not distortion (red channel). The situation was reversed for the "bad channels."Averaging all the channels we get a middle of the road score:Signal to noise ratio reflected the above issue with a-weighting resulting in substantial improvement of SNR:Our threshold of heaving in low frequencies is quite high so this is not as big of a problem audibly as it is in measurements.Frequency response was very good, almost ruler flat in audible band and going beyond 100 kHz at -3 dB:Crosstalk between channels 1 and 4 were rather disappointing:It is closer to a $29 amplifier than our state of the art Benchmark AHB2.The meat of the review is power measurements versus distortion. So let's get into that at 8 ohms:Nice to see the massive improvement relative to a higher end AVR (NAD T758) but as soon as distortion takes over, that advantage is sadly lost. We do get a few more watts though than our AVR.Here is the same measurement with 4 ohm load:Let's sweep from 20 kHz to 20 Hz and see how much power we get with THD+N set to 0.1% (barely or not audible distortion):We see a small drop in power at the extremes which is good.Some of you have been demanding that I work harder and measure performance with more than two channels. So here you go:I could not get the amplifier to distort less than 0.1% with 4 channels regardless of output level. So I stepped that up to 0.2% to get the third graph. I could have been watching a movie instead of running these extra tests so I hope you are happy!The Emotiva BasX A-500 seems to be a decent shot at building a 5 channel amplifier for a very decent price. Yes, it is a bit of a gamble how good each channel is, and how audible that mains hum can become. Other than that, it is a definite step up very amplifiers in AVRs.Overall I can recommend the A-500 if you are on a budget and have a bad back stopping you from lifting something heavier.--------As always, questions, comments, corrections, etc. are welcome.Do you work on weekends? I didn't think so. As you see, I am working, having produced two reviews instead of enjoying the last bit of sunshine we are having. So please, reach deep in your pocket and empty every dollar you have in my coffers using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/