This is a review and detailed measurements of the Fiio K5 Pro DAC and headphone amplifier. It was kindly sent to me by the company. The K5 Pro is a budget product, costing US $150 on Amazon with free shipping.The Fiio K5 looks decent and sports a nice, large volume knob which I appreciated:As you can see, there is the usual input selector and triple gain setting. An informative LED light around the volume control changes color depending on whether the device is in use.The back panel is as you expect:The power supply is rather unique, outputting 15 volts which typically indicates good power delivery when it comes to headphone output. Note that on AC side of it, the removable cable has the three-pin, round holes like laptop power supplies do.The rear Line Out changes with volume on the front but not the gain switch. The headphone output and rear Line Out are active at the same time so you have to remember to disconnect one or the other if that is what you intent.As usual, we start with our dashboard, measuring what comes out of the line out:Well, this is disappointing. I almost put aside the unit thinking it is not worth testing more. The SINAD puts it in the fourth quadrant of all DACs tested:Oops, forgot to mark which one it is in that graph. Sorry about that.Click on it and you should be able to find it.Note that SINAD improves good bit to 90s when the output is lowered to 1 volt or so.Before giving up, I ran a power test on its headphone out and found that quite good. So I continued with testing that port, rather than line out.Here is our jitter test:That's quite good as indicated on the graph. Worst case jitter components are at -135 dB which is way, way lower than threshold of hearing.Linearity really impressed me:Intermodulation+noise test shows some weakness but nothing badly broken:Here is our dynamic range:Good enough on 2 volt dynamic range but middle of the road on 50 millivolts of output:Most important test is power versus noise and distortion:We see that the Fiio K5 Pro has a lot of power, running neck and neck with Topping DX3 Pro. Yes, distortion rises at the limit but there is no clipping.Here it is at 33 ohm:We have nearly 1 watt of power into 33 ohm load!Output impedance is comfortably low:And channel balance as expected is perfect due to digital attenuation in the DAC:I started testing with my new DROP + MRSPEAKERS ETHER CX headphones which have a very low, 25 ohm impedance. The Fiio K5 Pro was comfortable to drive them hard and very well. Maybe at the last 5 to 10% of the volume it got a bit distorted but in any reasonable listening scenario, it was very comfortable and satisfying.The experience with Sennheiser HD650 improved yet again. There was enough power to even vibrate my earlobes!Excellent dynamics were there as a result with great bass and overall joy.The typical approach in a product like this is to build a DAC that performs very well. And then throw in a headphone amplifier that is just adequately. Here, the DAC is just good enough to drive the amp. The amp is designed to produce a lot of power and at low enough distortion to not be an audible issue. For a budget product and its intended use which is with headphones, it is a fine compromise.In that regard, and in the context of a budget product that is designed reasonably well,------------As always, questions, comments, recommendations, etc. are welcome.As you can tell I am working overtime in the night shift to produce the second review of the day. There is just so much gear to review. You don't have to pay me overtime but the panthers are saying the law requires them to be paid time and a half. So pleaseusing: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/