This is a review, detailed measurements and comparison of Monoprice Liquid Spark, Schiit Magni 3 and JDS Labs O2 headphone amplifiers. The Liquid Spark and Magni 3 retail for $99 but only the Monoprice comes with free expedited shipping. The JDS Labs O2 retails for USD $139 on US Amazon with free Prime shipping. JDS sells it direct for $129 plus shipping. So roughly speaking, all three are in similar price range.The three headphone amplifiers look very different from each other:As you see, the liquid spark is quite chunky compared the other two. It also generates a bit of heat although nothing remotely of concern.Connectivity is funky on the JDS O2 with 3.5 mm headphone jack for input. The other two have proper RCA inputs in the back and 1/4 inch in the front.The Liquid spark comes with a large laptop style external switching supply. The other two have heavy linear wall-wart supplies with the Schiit Magni 3 being quite a bit larger than JDS Labs O2.Let's get into measurements and see how the Liquid Spark performs.As usual, I start with my dashboard measurements. The first experience here was quite disappointing but with fiddling with grounding performance came up substantially:Usually the performance is limited by harmonic distortion but here, we have an odd 30 Hz hump that is the limiting factor. It is odd that it is a subharmonic of mains frequency. Usually I see the typical 60 Hz hum which is also here but is dwarfed by the 30 Hz tone. Fortunately we are pretty deaf in that region of audio frequencies so not an audible concern but strange nevertheless.Measuring dynamic range we get middling numbers:To put that in context I have started to collect these numbers in one place. There are some issues with how this is measured which I don't quite like but here it is anyway:As we see, the other two amps are significantly better in this regard.Frequency response is ruler flat and no concern at all:Output impedance likewise is very low and fine at just 0.8 ohm:Here is the power measurements at 300 ohm with low and high gain:There is not much more power in high-gain so if you can, use it in low gain mode to get the benefit of lower noise and distortion.Here are the results at 33 ohm:Well behaved amplifiers usually perform excellently until they run out of current or voltage and have that sudden clipping rise in distortion. Here, we have that toward right of the graph but also an early onset of distortion due to some other factor at just 20 milliwatt.For grins, I left the performance of the exceptional Massdrop THX AAA 789 in there at the bottom just in case you have another $250 to spend on a headphone amp.The Massdrop unit is essentially distortionless until max power.I had previously reviewed both the Magni 3 and O2 but looking back, I see that I used different templates and settings for measurements which make comparison challenging. So I re-ran the tests using the same setup as here. First, let's compare the Schiit Magni 3 to Liquid Spark using 300 ohm load:As noted in signal to noise ratio, the Schiit Magni 3 is quieter and produces more power than Liquid Spark.The picture changes with 33 ohm load:Here, the Magni 3 went kind of wild, starting to distort at just 4 milliwatt. What's worse is that performance varied fair bit from run to run! And regardless, its is worse than Liquid Spark. Neither is to my liking here although if I had to pick one, it would be the Liquid Spark.Let's do the same comparison against O2:The O2 has much lower noise but falls short of Liquid Spark in power. I think the O2 is power supply limited. I might turbo charge it with a bigger supply one day and see what happens.Here is the 33 ohm comparison:This was weird as one channel in O2 became a lot more noisy. Not sure what is going here. Maybe the 3.5 mm jack is lose or something. Regardless, we see the same lower power output and potentially lower noise if we just look at the good channel.So not a clear cut picture.I started the testing by comparing the Magni 3 to Liquid Spark. I connected both using a split RCA cable to my Topping DX3 Pro . I played a tone and then level matched both using my Audio Precision analyzer. AB tests with either Sennheiser HD-650 and HiFiMan HE-400i did not show any audible difference at first. Soundstage, noise, resolution, etc. was all identical. Finally on a bass heavy track at leaves approaching hearing damage, I managed to find one instance where the bass got distorted in Liquid Spark but stayed clean in Magni 3. I could not repeat this with any other tracks at exceedingly high playback levels.I then organized the same comparison against the JDS O2. At first I could easily hear change in sound stage and even fidelity but then realized that the channels were swapped in O2. I fixed that and the difference went away. Without risking hearing damage, I could not push either amp further to cause any differentiation in delivery.So I would say this is essential a three-way tie with a tiny nod toward Magni 3 at exceedingly high output levels.While there are a few oddities here, this is the first Alex Cavalli design that I have tested with competent performance and at hugely bargain price of just $99 including shipping. It joins two other good products, the JDS Labs O2 and Schiit Magni 3. The O2 has more of a textbook performance but slightly less power. The other two have more of a boutique performance with their distortion rise at low load impedances.Listening tests show the three in dead heat with essentially nothing differentiating them.So I say base your purchase decision on company reputation, form factor, looks, availability, etc.For now, theAs always, all questions, comments and criticism is welcome.-----If you like this review,using Patreon ( https://www.patreon.com/audiosciencereview ), or upgrading your membership here though Paypal ( https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054 ).