Review: Music Angels Mengyue Mini Tube Integrated Amp

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Adventures in Chi-Fi, Part 贰

The front side of the Mengyue Mini tube integrated amplifier
The Mengyue Mini uses EL-84 tubes, found mostly in output stages of small amps. Brent Butterworth

One of the products that caught our attention while browsing for some cool stuff (you can see the rest in our list of 8 Remarkably Quirky Yet Awesome Chi-Fi Audio Products) was the Music Angels Mengyue Mini. This little EL84-based integrated amp has a wild design; the EL-84 is a tube used mostly for the output stages of small amps. And for the price, the Mini seems like an amazing deal, especially if you feel that the Chi-Fi trend deserves some deeper exploration.

With its real wood trim panels, arcing handles, and textured black paint job, the Music Angels Mengyue Mini's styling rises far above the cheezy cosmetics of most cheap Chinese amps – and for that matter, far above a lot of American-made tube amps.

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Mengyue Mini: Out of the Box

A close up of the Mengyue Mini tube integrated amplifier
The Mengyue Mini features real wood trim panels, arcing handles, and textured black paint job. Brent Butterworth

After weeks' worth of waiting, the Mengyue Mini arrived in excellent condition, packed in a padded box with labels for the proper sockets. Don't be alarmed if the packaging smells strangely like a Harbor Freight store – if you've ever been in a Harbor Freight, then you know the smell we're talking about.

After following the directions, we connected the amp to a pair of Dayton Audio B652 speakers, plugged the amp in, and flipped the power switch. That Harbor Freight smell intensified as the paint heated up, but at least nothing smoked. We connected an iPod Touch, set it to play every song loaded on it, and let the Mengyue Mini amp run for about 10 total hours. With nothing strange or out of the ordinary having happened, we connected the Mini to a pair of Revel Performa3 F206 speakers.

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Mengyue Mini: Features

The rear panel of the Mengyue Mini tube integrated amplifier
The Mengyue Mini's connections are as simple as they could be, despite flipped RCA jacks. Brent Butterworth

• 15 W/channel (rated) into 8 ohms
• 2 line-level audio inputs
• 4 EL84 power tubes, 2 6N3 low-level tubes
• Dimensions: 5.5 x 10.2 x 8.3 in (140 x 260 x 210 mm)
• Weight: 16.5 lb (7.5 kg)

The Mengyue Mini barely has any features to speak of. There's just two line inputs and a pair of five-way binding posts for speaker connections. It works for us, since we need only two inputs: one for the phono preamp from a record player and the other for whatever USB DAC happens to be in use for the week.

The only downside to the whole package was that the bottom plate covering the circuitry was scuffed up, like it was scavenged off a unit that came in for repair. We pulled the bottom plate to find a conventional printed circuit board. We noticed the four trimmer pots for biasing the output tubes, but there are no labeled contacts for measuring the bias. And, of course, the manual isn't particularly illuminating.

From the testing that we were able to perform, we found that the output tubes were overbiased to 15 W instead of the EL-84's max-rated 12 W. This can be an important factor for those who want correctly-biased tubes that will last longer and perform better over time. Just keep in mind that doing so is a very technical procedure and can put fingers within dangerous proximity to a few hundred volts of electricity. So be careful.

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Mengyue Mini: Setup and Ergonomics

The manual for the Mengyue Mini tube integrated amplifier
Don't expect too much info from the included manual for the Mengyue Mini. Brent Butterworth

The Mengyue Mini's connections are as simple as they could be. The only thing unusual is that the input jacks (RCA) are flipped, so the right (red) channel is on top and the left (white) channel is on bottom. They're also tilted a little, but at least  they're correctly color-coded.

As for the manual, it's mostly in Chinese and devotes just one page to the Mengyue Mini. The good news is that you don't have to feel bad about not knowing Chinese, since there isn't a whole lot of information provided about the product as it is.

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Mengyue Mini: Performance

The inside circuit board of the of the Mengyue Mini tube integrated amplifier
Nothing fancy inside the Mengyue Mini, just a conventional printed circuit board. Brent Butterworth

We compared the Mengyue Mini to a Krell S-300i integrated amp, which is rated conservatively at 150 W per channel into 8 ohms. Levels were matched, the Revel speakers were connected, and a Firestone ILTW USB DAC sourced signals to both amps. We selected a moderate listening level loud enough for to judge the sound quality, but not so loud that it would frequently tax the Mengyue Mini's comparatively low output.

One of our all-time-fave testing tracks, Holly Cole's version of "Train Song," told us a lot about the Mengyue Mini. There are no obvious sonic colorations or flaws, and the Mini is able to handle the strong, super-deep bass notes without audibly distorting. Cole's voice sounds exceptionally smooth and charming. The hand percussion that punctuates the song comes across as detailed enough, and the bass has a just-slightly fat, pleasing quality to it.

When we switched to the Krell amplifier, the bass tightened up a lot, sounding punchier and more precise. The percussion sounds a lot more vivid and detailed, the soundstage is deeper and broader, and the imaging is far more precise than what we hear from the Mengyue Mini. However, Cole's voice sounds a little cold and almost mechanical in comparison; the same applies with Donald Fagen's voice on Steely Dan's "Aja."

The results weren't surprising; they conform to audiophiles' general perceptions of what tube amps sound like. But the results didn't conform to our preconceptions when we played Dwight Yoakam's duet with Maria McKee, "Bury Me Along the Big Sandy." The recording sounds bright to begin with – mid-1980s digital at work. But through the Mengyue Mini it actually sounds brighter, as if someone had turned up the treble one notch. And although it doesn't obviously distort, it also doesn't have enough oomph to get the tune's tight bass line right. So, subjectively, the tonal balance ends up a little fatiguing.

When we switched back to the Krell amplifier, the bass line got tighter, punchier, and provided a better counterbalance to the too-bright vocals and guitar.

David Chesky's musically and technically fantastic album, The Body Acoustic, also readily reveals the differences between the two amps. Through the Krell amp and Revel speakers, the sound of the opening cut, "52nd Street," is everything an audiophile could want: deep. dynamic, ultra-spacious, haunting, and precise. Through the Mengyue Mini, that track still sounds nice, but the piano and bass clarinet sound softer, less detailed, and less spacious. Only the bass shows improvement with the Mengyue Mini, seeming to exhibit more character and subtlety. Or it could be clarity or sonic coloration –  only Chesky and bassist Andy Gonzalez could opine on that topic with any authority.

We also spent dozens of hours casually listening to the Mengyue Mini with the Revel speakers, fed by a Pro-Ject RM-1.3 turntable and NAD PP-3 phono preamp. The sound output is consistently enjoyable! While the Mini may be a long ways from perfect, it can definitely satisfy, especially if you want something to play old jazz records on. It plays louder than expected, too, easily hitting peaks around 95 dB.

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Mengyue Mini: Measurements, Part 1

Frequency response chart for the Mengyue Mini tube integrated amplifier
Mengyue Mini's frequency response, with the left channel (blue trace) and right channel (red trace) referenced to 1 W at 1 kHz. Brent Butterworth

After a couple of weeks of listening, we moved the Mengyue Mini to a test bench to observe its technical performance. With the Mini connected to a Clio 10 FW audio analyzer and some load resistors, we booted up the Clio and prayed nothing would catch fire and scorch the test bench (it didn't).

Frequency response
-0.55/+0.31 db, 20 Hz to 20 kHz
-3.71/+1.25 dB, 10 Hz to 50 kHz

Signal to noise ratio (1 W/1 kHz)
-60.1 dB unweighted
-79.2 dB A-weighted

Total harmonic distortion (1 W/1 kHz)

Crosstalk (1 W/1 kHz)
-62.4 dB left to right
-62.2 dB right to left

Channel imbalance (1 kHz)
+0.27 dB high in right channel

You can see the frequency response in the chart above, with the left channel (blue trace) and right channel (red trace) referenced to 1 W at 1 kHz. None of these numbers are great, but for a cheap, primitive tube amp, they're not disappointing either. Except for the distortion, which runs rather high even for a tube amp.

The rising high-frequency response, which can result in stability problems (i.e. oscillation, otherwise known as the amp self-destructing), was a concern at first, but the Mini survived many hours of listening with somewhat-abusive test bench sessions without any issues.

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Mengyue Mini: Measurements, Part 2

Watts versus distortion chart for the Mengyue Mini tube integrated amplifier
The Mengyue Mini's power output in watts versus distortion, measured with a 1 kHz signal. Brent Butterworth

Here's what can put the minds of American and European boutique hi-fi manufacturers at ease. The chart above is the Mengyue Mini's power output in watts versus distortion, measured with a 1 kHz signal with both channels driven (orange trace) and one channel driven (purple trace) into 8 ohms. One can only get so much out of EL-84s, but even so, the Mini's measurements here are pretty weak.

Power output (1 kHz/8 ohms/2 channels)
3.2 watts RMS at 1% THD
10.6 watts RMS at 4.6% THD

By my normal standards (1% THD), we'd rate the output at just 3.2 W. Strangely, we couldn't push the Mini above 10.6 W even by raising the output level and the maximum distortion threshold of the Clio analyzer.

Also, the amplifier can barely drive a 4-ohm load resistor at all; we can't even push it to 1 W of output for the measurements, and the Clio analyzer isn't able to get enough signal out of it to do a power output versus distortion measurement. We're no tube amp scientists, but something seems amiss with the Mengyue Mini's engineering and/or the components here.

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Mengyue Mini: Final Take

A closeup of the Mengyue Mini tube integrated amplifier's glowing tubes
Despite its flaws, the Mengyue Mini does draw visual attention. Brent Butterworth

Does the Mengyue Mini give traditional high-end audio manufacturers anything to worry about? Our answer is probably not. Although this amplifier looks great and sounds fine, it's technically pretty dicey. It's questionable whether or not the Mengyue Mini would meet any recognized safety standards (although many high-end audio products don't). The company website says the product is guaranteed for one year, but what legal recourse do you have against the manufacturer if they refuse? Besides, it's not particularly cheap to ship products overseas for repairs or service.

Still, the Mengyue Mini can be considered an amazing deal if you just want a cheap little tube amp to play with. People who see it frequently exclaim, "Ooh, how cool!!" when we show them how it works – our Krell amp never gets that kind of attention.

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