This is a review and detailed measurements of the Crown XLS2502 DriveCore (switching) 2-channel amplifier. It is on kind loan from a member. The XLS 2502 cost US $645 including free shipping from Amazon. It has DSP functionality which I did not test. And is specified to drive 2 ohm load.From the outside, the XLS2502 is built like a tank:It is very light of course due to switching topology for the amplifier and power supply. But also very sturdy with plenty of steel to keep its shape.The two gain controls are notched which gives them a nice feeling but the gain is not matched and is hard to get there using those notches.Here is the back connectivity:There is a fan as you see but in normal testing it never came up. During stress testing, it did come on but was pretty quiet compared to what I expected. Mind you, I don't think you want it close to you if it is going to be running.Alas, the fan was insufficient to keep the unit cool under full power. The red thermal indicators came up even though the fan was running. The amp seemed to be functioning still but to be on the safe side, I terminated my testing there. In typical home use, even for subwoofer duty, I doubt that this is a concern as you will see later as far as what wattage we are talking about.Overall, the impression of the amplifier is positive, making you think you have something made to be run over by a car and still function reliably.As usual we start with our dashboard of 1 kHz tone into 4 ohm load at 5 watts:I set the gain to 29 dB for consistency. I also tested it at 19 dB gain and it only made 1 to 2 dB improvement. The reason is that SINAD (signal relative to noise+distortion) is dominated by harmonic distortion. Here, those harmonics are very high order which perceptually is not very good as they are not masked as easily. Anyway, with a SINAD of 71 dB, we have below average performance:The XLS1502 did a bit better in this regard, garnering a SINAD of 77 dB.Frequency response shows the same sharp cut off:I don't know if this can be changed using DSP programming or not.Above is with resistive load. Switching to a simulation of a 2-way speaker gets us little difference:So there is some speaker dependency but I would not lose sleep over it.Crosstalk is OK but could be better:The red line is a $30 amplifier by the way.32-tone test signal simulating "music" gives a more hopeful picture of distortion:The spray of harmonics is high in frequency where our hearing threshold is higher.Signal to noise ratio is poor at 5 watts but gets better at full power:Lower gain settings may improve this a few dBs.You don't buy this amplifier to listen at 5 watts so let's see what it can do when its wings are given enough room to fly:Wow! Nearly 500 watts of power is delivered into both channels simultaneously. The good news doesn't end there. Check out these ratings when distortion is relaxed to 1%:1600 watts of peak power is delivered out of standard 120 volt outlet! These thing is a powerful beast.Noise level is decent but I wanted to make sure the high gain was not impacting it. So I reduced gain to 19 dB which required some 6 volts of input to drive to clipping:There is no difference at all.For the rest of these tests I stayed at 19 dB gain. Here is the power output with 8 ohm:Over 300 watts at what should be inaudible distortion for most people.Finally we get to my stress test. I played with the settings because the high frequency noise shaping would not let me perform the sweep. So I decided to change this test and set the limit to 22.4 kHz (instead of usual 90 kHz) and limit the sweep to 6 kHz. That way, the third harmonic of 6 kHz (18 kHz) is still included in the computation. No music has full power at high frequencies anyway so I don't think we need to keep measuring to 20 kHz with respect to power. Here is the output:As noted, the red warning lights came on as the sweep was going from right to left so I terminated the test. Delivered output was about 520 watts which is still plenty but is naturally lower than 1 kHz which was in high 600s.These pro amps have mastered the technique of delivering tons of power with distortion and noise kept under control. Lack of power is the #1 reason an amplifier can sound bad. Don't care how good the SINAD is at 5 watt. If you run out of power, you will hear distortion, lack of dynamics, etc. So if you need the power, it is best to get it than to have less of it. And on that front, the Crown XLS 2502 delivers tons of it, breaking all previous records for any amplifier I have tested. The price is ridiculously low for the amount of power you get as well.Ideally, you would use more finessed amplifiers above bass frequencies and use the XLS 2502 to drive the subs. But if not, the XLS2502 can deliver good performance.Overall,------------As always, questions, comments, recommendations, etc. are welcome.It is two minutes to midnight. Getting my panthers to model this late at night is costing me overtime pay at 2X their normal hourly rate. So while my time is free, theirs is not. So please