This is a review and detailed measurements of the Violectric HPA V281 headphone amplifier and preamplifier. It is on kind loan from a member who has been waiting a while for its review.The V281 comes in different versions with the bass unit costing US $1,999. The version I have has remote control with stepped attenuator, raising the cost to US $2,500.The V281 has a look which would be at home in a recording studio:I like the massive volume control but it is a bit loose. The rest of the controls all feel good and bring you think you bought a quality product.The back panel shows fair bit of control and connectivity:For my testing, I used the XLR connections. I am not a fan of dip switches for gain control. You have to keep messing with them if you use different headphones that require different gain. That said, once you read the measurements you will see that the standard gain (all switches down) provides almost full power and lowering the gain beyond that, does not help with noise level anyway.There is a DAC option which the test unit does not have.As is typical of these stepped attenuators using relays, you can often hear glitches as you turn the volume control fast.Since there is a provision for analog in and out, I figured I test the unit that way first. Here is our dashboard:This is very good but not excellent. What was strange and not matching the specifications was the low frequency roll off:Signal to noise ratio is very good but again, shy of excellence:Intermodulation distortion versus level shows what we already know:Here is our usual dashboard:Wow, that is quite a bit better than the pre-amp pipeline. Distortion is solidly in inaudible range placing the V281 in our upper tier of all headphone amplifiers tested:Noise performance is the same as preamplifier measurements and gets much worse as we lower the output to just 50 millivolts:So likely not a good fit for sensitive IEM listening. Searching online, I saw comments about hiss with such devices confirming our measurements here.Intermodulation distortion versus output power level shows ample amount of latter with higher noise level as we would predict:Let's look at the THD+N versus output power starting with 300 ohm:We an incredible 1.5 watts of power into such a high output impedance. Violectric brags that the internal voltages are as high as 60 volts (likely +- 30 volts) and it shows.Note that even the baseline gain gets you 366 milliwatts of power so you should really not need other gain settings unless your input signal is very weak.Switching to the other extreme at 33 ohm we get:Since it clipped already, I did not bother to test with higher gains. Once again we have plenty of power at 2 watts and elevated noise levels.Switching to 50 ohm load and comparing both XLR and 1/4 outputs we get:XLR output did not give us more power so I am assuming it is a convenience feature and not differential output. That is fine anyway as there is no benefit other than power there and we already have plenty of power. Some reviewer said the XLR was louder though. I looked but could not decipher the specifications for V281 in this regard. So I am sticking with my measurements.: Looks like it was current limiting that stopped it from producing more power at 50 ohm. At higher impedances the power should double as shown by the designer later in the thread.Channel matching was perfect due to stepped attenuator:Output impedance was very low (and therefore good):I started with my very low impedance (25 ohm) closed back Drop Mrspeakers Ether CX . To say there was ample power to drive these in baseline gain setting would be an understatement. Bass performance as a result was fantastic as was dynamic range.Switching to Sennheiser HD650 headphones proved the same with powerful presentation with no hint of distortion whatsoever.No, there is no magic in its sound with respect to soundstage, etc. There has not been such magic in any headphone amplifier I have tested.The Violectric HPA V281 sports a serious, professional looking feel and design to headphone amplifiers. Other than higher noise floor than state-of-the-art headphone amplifiers, and rolled off low frequencies, its design is without fault. Clearly great attention has gone into it from start to finish.The price is of course sky high. With it, you get a unique looking headphone amplifier and preamp with balanced XLRs in and out. You would have to be a judge of these set of trade offs. My job is to look under the hood and tell you if it is sound and the answer is definitely YES. As such,------------As always, questions, comments, recommendations, etc. are welcome.I am getting worried about sitting at my desk so much doing these reviews and not getting enough exercise. Fortunately I saw on TV they have a set of wheels you can peddle while sitting at your desk that lets you lose 30 pounds in 30 days. Yippee! Need some money to buy it so pleaseusing : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/