I've covered a number of high-end headphones this year, but it's been a while since I've reviewed a desktop headphone amplifier designed to bring out the best in those headphones. So when Monoprice's $770 Monolith Liquid Platinum amp showed up on my doorstep, I had high hopes it would shine. The amp was accompanied by its pint-size little brother, the $100 Monolith Liquid Spark.

Before we go any further I have to talk about the amps' designer, Alex Cavalli. I've long admired the high-end headphone amps he designed for his company, Cavalli Audio. Sadly, that company closed shop, but the good news is Cavalli is now designing much more affordable headphone amps for Monoprice. 

Meet the Monolith Liquid Platinum

The amp's front panel is straightforward, from left to right there's a power button, 6.3mm headphone jack, a second four-pin stereo XLR balanced headphone jack, volume control knob and a tiny button that switches between the balanced XLR and single-ended RCA inputs. There's also stereo RCA outputs. That's it, the Liquid Platinum is an analog-only device, there are no digital inputs. What we get instead are two tubes poking through the top panel, they're Electro Harmonix 6DJ8 tubes. The Liquid Platinum's all-metal chassis feels solidly put together.

Some high-end headphones are insensitive beasts and need a lot of power to sound their best. That's why the Liquid Platinum can deliver up to 6.2 watts per channel, right up there with some of the most potent headphone amps I've tried. Even so, the Liquid Platinum is a desktop friendly size, a tidy 8.8 by 8.5 by 2 inches.

Meet the Monolith Liquid Spark

Don't for a second underestimate this little guy, the Liquid Spark isn't just powerful, it's one suave performer. It runs on an 18-volt filtered power supply that enables the Liquid Spark to produce up to 1.3 watts per channel with low distortion. The all solid-state amp has switchable gain for use with all types of headphones.

Looking at the front panel from left to right there's a power button, 6.3mm headphone jack, gain control button and the volume control knob. This little fella has stereo analog RCA inputs with preamp stereo RCA outputs, and it measures a scant 4.6 by 3.7 by 1.5 inches.

Liquid Platinum listening tests

The "big" Liquid Platinum just sounds right, sweet, yet detailed, bass is full, but not overly ripe. It drove every full size headphone in my collection with ease.

In a face off between the Liquid Platinum and Mytek Brooklyn headphone amps with the outrageously great Abyss Diana Phi headphones (review to come) it was easy to hear the two amps were quite different. The Liquid Platinum is more refined and pure sounding, the Brooklyn shrinks the soundstage and it sounds too lean and cool for my taste. The Liquid Platinum is in a different league with this very revealing headphone.

I next compared the two amps again with a much more modest Beyerdynamic T51p headphone, and again the Liquid Platinum's dynamic dexterity left the Brooklyn in the dust.

Moving to Sony's flagship MDR Z1R headphones, I compared the Liquid Platinum with a Schiit Lyr 2 tube headphone amp. The Z1R is an astonishing closed-back headphone, and the Liquid Platinum was a terrific partner, serving oodles of detail, excellent dynamic contrasts and airy treble. They were a total pleasure to listen to. 

The Lyr 2 was awfully good, the sound was palpable with terrific dimensionality, but it was no match for the Liquid Platinum's transparency. The Lyr 2 darkened treble detail, and dynamics were reduced, but the overall sound was still delicious with the Z1R. I'd call it a tie between these two amps.

The Liquid Platinum's other major design feature is its fully balanced circuitry. To determine if I could hear a difference I listened to the Diana Phi with the standard cable terminated with a 6.3mm plug, and then listened to the same headphone with an identical cable terminated with an XLR balanced plug. What can I say, the balanced connection might be a tad smoother, but if I have to struggle to hear a difference, then the difference isn't that big a deal.

So with either connection the Liquid Platinum is superb, a truly remarkable sounding amp for $770.

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Listening to the Liquid Spark

If the 'Platinum is out of reach, no worries, Alex Cavilli has something for you with the $100 Liquid Spark headphone amp. The sound with my Sennheiser HD 700s high impedance (150 ohms) headphones made it clear this is a very serious headphone amp. The sound is pure and dare I say it, beautiful. That's the best single word description of the sound, bass, midrange and treble ranges were smooth, yet at no loss for detail. Soundstage over the HD 700 was big and wide open, I could hardly ask for more.

I know my Audio Technica ATH M50x headphones well enough to notice the Liquid Spark smoothed out some of their treble hardness. Bass was round, with good impact and punch, making the M50x sound better than ever.

The Master & Dynamic MH40 on-ear headphones transparency excelled with the Liquid Spark. The MH40 unforced clarity brought them closer to what I've come to expect from high-end planar magnetic or electrostatic headphones. The Liquid Spark transformed the MH40.

With the Liquid Platinum and Liquid Spark, Monoprice and Alex Cavilli have two winners on their hands. Bravo.

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