|"BAS" on screen indicates I'm using the bass-boost EQ here.|
As mentioned previously, I found myself in the position of needing to update my computer workstation desktop speaker system. I figured, instead of staying with powered/active speakers, since I do have a few bookshelf speakers around the home, why not try some passives on the desktop as well?
While active speakers are great in that the built-in amplifiers and transducers can be well-matched and optimized, the ability to "mix-n-match" passive speakers while opening up the potential to upgrade amplifiers I think is fun for the hobbyist. As such, I found myself drawn to getting a small low-power Class D amplifier like this.
Since the amplifier will likely be left on 24/7, I wanted something that's highly efficient but provides adequate power. This SMSL device internally is powered by the Infineon Technologies MERUS MA12070 Class D amplifier which uses their "multi-level" modulation such that the switching output can have half-voltage levels which adds an extra level of control and power savings. The device is rated to provide up to 2x30W continuous into 8Ω or 2x80W into 4Ω but realize this is with 10% THD+N. What will be more interesting to me is how much power is available into something like 4Ω with ≤0.1% THD+N, and the noise this switching device produces. Let's see if this amp lives up to hopes of "high-fidelity" playback...
I. The amplifier itself...
To start, let's have a look at the SMSL device and a few of the physical features:
As you can see, it comes in a typical box. They have different color devices to suite your taste. The blue one I got looks nice and adds a little highlight to my tabletop without drawing too much attention to itself. Almost everything these days can have that Japan Audio Society "Hi-Res Audio" logo which originated back in 2014. Have a look at this quick slide set to see the meaning of that logo. Depending on the device, the "rules for approval" are variable and we have little assurance that a company conforms to a strict standard. For example, as an amplifier, the device has to have "amplification performance of 40kHz or above" - not exactly a difficult hoop to jump through ;-). For those interested, have a look at Mark Waldrep's discussions and critique.
Comparing the amp with the size of its power supply and cables, this is a small box! About 7cm/2.8" wide x 7cm/2.8" tall x 15.5cm/6.1" deep box (excluding protrusion of antenna and volume knob). The power supply is rated as 24V 6.75A. Workmanship on that CNC metal shell is nice with clean edges, solid little metal buttons for power ON/OFF, and source select (line in, Bluetooth 5.0 with aptX, and USB input). There's a larger turn/button press knob for menu settings which allows selection of EQ options, treble/bass tone +/-10dB, and color of the screen text. The LCD screen is always on; it's not bright or distracting on a computer desktop in use. I would have liked an option to dim the screen nonetheless.
The plastic remote is the typical light, inexpensive variety, 2xAAA batteries needed. It's convenient and replicates the front panel controls with an added mute button.
Here's a look at the rear:
II. Basic Characteristics
III. Single-Tone Harmonic Distortion and Noise
|Apologies that I had changed the display range for the 12V (36W) reading.|
As you can see, we're looking at results from 16mW to 36W to a 4Ω load. Overall, this looks pretty good. For the most part, distortion tends to be second order and starts to transition around 6V and by 12V, the third order predominates. We'll graph the THD(+N) vs. power a little later.
IV. Multitone Testing - Intermodulation Distortion and Triple-Tone TD+N
V. Subjective Listening
VI. In Summary...
|A look at the setup menu with Input (USB/Line In/Bluetooth), EQ selections (like "Super Bass", "Rock", etc...), Treble/Bass control, screen color (blue/yellow/cyan/orange/purple), and "BT Clear" to unpair from devices if you scroll down. |
"In our tests, however, it sounded slightly thin, and both our ears and our measurements indicated that it was noisier and had higher distortion at low levels than our picks."