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Monolith by Monoprice Liquid Spark headphone amplifier by Alex Cavalli

Monolith by Monoprice Liquid Spark headphone amplifier by Alex Cavalli

After a distinguished 18-year career in audio circuit design, Dr Alex Cavalli shut down Cavalli Audio and retired as an industry heavyweight. Cavalli made it known he would rather stop short his famed run rather than sacrifice his reputation for quality, performance, and sensible prices. Recently, however, Cavalli has found the right partner in California-based Monoprice to restoke his fires and give headphone amplifier design another go, starting with the introduction of the Monolith by Monoprice Liquid Spark headphone amplifier. Cavalli Audio once planned a portable amplifier to be named the Liquid Spark, so this amp pays homage to a product that might have been. This is great news to those of us who lamented Cavall’s retirement, but even better news is that Monolith’s Spark will retail for the rock bottom price of £76. While some of you may have rolled your eyes on hearing this price (thinking good things must cost more), don’t sleep on this extremely small headphone amp as it really packs a punch and lives up to the reputation Cavalli so carefully crafted over the previous two decades. 

The Liquid Spark uses a DC-coupled topology from the input to the output stage and is a fully discrete design. This approach eliminates the need for capacitors and op-amps in the signal path that might colour the overall sound. At the differential input stage the Liquid Spark uses laser-matched, low-noise audio JFETs instead of traditional bipolar transistors. JFETs are known to perform well in low-level applications, producing little noise while at the same time providing high input impedance. The output power stage employs high performance MOSFETs, which are ideal for designers looking to provide high power and very clean amplification within tight space constraints. The net result is a compact headphone amplifier that employs dual 18V filtered power supply rails that produces a convincing 1300mW RMS per channel into 50 ohms with very low distortion. With adjustable gain on the front panel, the Liquid Sparks exhibits a remarkable ability to produce a full sound that is crisp, quick, and sits quite comfortably in comparison with headphone amplifiers double or even triple its cost, as we will discuss shortly. 


The affordable Liquid Spark isn’t going to wow you with an array of flashy dials or features, as this rather bare bones amplifier banks its value on what really counts: the sound. However, one exciting feature that deserves mention is found on the back panel where a user will see two sets of RCA jacks, one of which is a preamp output. The preamp outputs are controlled by the volume knob on the front of the amplifier and can be tailored to control entry-level powered speaker systems, or other power amplifiers.

I auditioned the Liquid Spark with multiple pieces of music, but for this review I selected Furry Lewis’ ‘St. Louis Blues’ [Fantasy] as a baseline. The hauntingly sparse blues guitar and vocal combination inherently would allow plenty of space to help detect just what this little pitbull of a headphone amp could sink its teeth into. The Liquid Spark picked up and polished all the micro details of Furry’s uncanny buzzing slide guitar sound that I previously thought only were audible with my reference Oppo HA-1 (10x more expensive than Liquid Spark). The Liquid Spark produced an impressively wide soundstage and a three-dimensional presentation that made the listening experience sublime. Impressed start to finish I have to truthfully say that the Liquid Spark gave me over 90% of what I was accustomed to hearing from the HA-1 in every discernable metric. 

For those of us (and I think there are many) who appreciate that last sonic 10% but don’t feel driven to pay through the nose for it, let me firmly encourage you to go pick up the Monolith Liquid Spark. The Liquid Spark offers outrageously good value for money and is exactly the headphone amp you need (or some fledgling audiophile close to you needs), whether building a first headphone system, or adding headphone capabilities to an existing system.


Type: Solid-state DC coupled headphone amplifier 

Inputs: One unbalanced analogue input (via RCA jacks)

Outputs: One 6.35mm headphone jack, on variable-level preamp output (via RCA jacks)

Frequency Response: 10Hz – 50kHz, +/- .05 dB

Power output: >7.6v/ 90mW (@600 ohms) Balanced, >3.8v/ 45mW (@300 ohms) S-Balanced 

SNR: 108dB (ref. 1 Vrms input / 2 Vrms output @ 1kHz)

THD + N: <0.006% Balanced, <0.005% S-Balanced

Crosstalk: -83dB

Gain: +3dB or +6dB

THD + N: 1VRMS (20mW) – 0.007% THD at 1kHz both channels. 

5VRMS (530mW) – 0.035% THD at 1kHz both channels

Dimensions (HxWxD): 1.5″ × 4.5’’ × 3.75’’

Weight: 252 g

Price: $99 US, £76


Monoprice, Inc. 

11701 6th Street, Rancho Cucamonga, CA 91730 USA

+1 (877) 271-2592



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