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Review and Measurements of Monoprice Liquid Spark Headphone Amp

amirm

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#1
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:

Monoprice Liquid Spark Headphone Amplifier review.jpg

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.

Measurements
As usual, I start with my dashboard measurements. The first experience here was quite disappointing but with fiddling with grounding performance came up substantially:
Monoprice Liquid Spark Headphone Amplifier Measurements.png


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:
Monoprice Liquid Spark Headphone Amplifier Signal to Noise Ratio Measurements.png


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:

Monoprice Liquid Spark Headphone Amplifier DNR Table Measurements.png


As we see, the other two amps are significantly better in this regard.

Frequency response is ruler flat and no concern at all:

Monoprice Liquid Spark Headphone Amplifier Frequency Response Measurements.png


Output impedance likewise is very low and fine at just 0.8 ohm:
Monoprice Liquid Spark Headphone Amplifier Output Impedance Measurements.png


Here is the power measurements at 300 ohm with low and high gain:
Monoprice Liquid Spark Headphone Amplifier power at 300 ohm Measurements.png


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:
Monoprice Liquid Spark Headphone Amplifier power at 33 ohm Measurements.png


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.

Comparisons
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:

Monoprice Liquid Spark Headphone Amplifier Compare to Schiit Magni 3 Measurements.png


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:
Monoprice Liquid Spark Headphone Amplifier power at 33 ohm versus Schiit Magni 3 Measurements.png


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:
Monoprice Liquid Spark Headphone Amplifier Compare to JDS Labs O2 Measurements.png


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:
Monoprice Liquid Spark Headphone Amplifier power at 33 ohm versus JDS Labs O2 Measurements.png


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.

Listening Tests
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.

Conclusions
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, the Monoprice Liquid Spark gets my recommendation.


As always, all questions, comments and criticism is welcome.

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Ron Texas

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#3
Another highly relevant review of available, budget priced gear in a popular category. How was the Liquid Spark at driving HD650's to loud volumes?
 

amirm

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#4
Another highly relevant review of available, budget priced gear in a popular category. How was the Liquid Spark at driving HD650's to loud volumes?
Excellent. Plenty of power is available.
 

mi-fu

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#6
Thanks for the review, Amir! Glad to see that the measurement is decent.

Will you have a chance to test the RCA preamp output of the Liquid Spark?
 

Jorj

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#8
@amirm, I noticed that your dashboard is showing around 1Vrms, instead of the 2Vrms that you normally use. Is this intentional (or consequential)?
 

amirm

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#10
@amirm, I noticed that your dashboard is showing around 1Vrms, instead of the 2Vrms that you normally use. Is this intentional (or consequential)?
For DACs I always use 2 volts. For amps using unbalanced, I had been using 1 volt for O2 and Magni 3 review so went with the same.
 

restorer-john

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#11
@amirm, I noticed that your dashboard is showing around 1Vrms, instead of the 2Vrms that you normally use. Is this intentional (or consequential)?
Amir did it on purpose to make sure people were checking his numbers. :)
 

flipflop

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#12
Since you recommend this product, wouldn't it be a good idea to be a bit more thorough and include a channel matching vs gain measurement?
 

amirm

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#14
Since you recommend this product, wouldn't it be a good idea to be a bit more thorough and include a channel matching vs gain measurement?
Ooops. I forgot to post that:
Monoprice Liquid Spark Headphone Amplifier Channel Deviation Measurements.png
 
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#15
Hi Amir, any chance to see how these do with a real headphone load vs. a dummy load. Maybe the same headphones you used on the TXH AAA 789.

Would be great to make that a standard measurement for headphone outputs given that is what this gear is for :)
 
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#17
Great matchup! I was hoping to see O2 measurements on the new equipment. Great! If I read the graph correctly, O2 distortion of about 0.0007 at around 50mW is a good number for 16DB of gain. Could you run the power sweep at low gain also? I am assuming that your O2 has the stock 2.5x, 6.5x gains.

In previous review of O2, we also didn't see THD vs freq.
The same goes for Topping A30. We never got to see dist v power at either medium or low gain.

Regarding putting a bigger transformer on O2, aren't you limited by the internal regulator, 12V?
 

garbulky

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#18
I am impressed. The market for affordable amps that perform really well is really something now. I don't think these kind of measurements were the case 5 to 10 years ago. I am dissapointed at the overall actual power outputs on most of the headphone amp offerings. What's stopping amps from much heftier power outputs at clean levels? But I guess if they get loud enough for your purpose and still sound excellent that's what matters. Thanks for reviewing these.
 
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#20
Hi Thomas. Headphone tests are rough on the headphones and our dogs. :) So I tend to only do them on request. I will take a shot on this and report back.
Thank you so much. I see the problem with the dogs...

It might be worthwhile to think about the test parameters. Maybe calibrate the volume to 90db at 1KHz on your test head for a given headamp / headphone combo and then do the frequency scan.

That would provide the real world performance of a given amp with a couple of headphones.

Cheers

Thomas
 
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