As you can see, the reviewer linked above gave the product some positive comments on the sound. I was curious to listen and since we know that Class D amps like these are very efficient, how about we run the playback system - music streamer to amp to speakers - completely wirelessly and battery powered for a listen also?
In order to run this without being plugged in, I got one of these battery packs:
That's a Talentcell 12V/8300mAh, 9V/11000mAh, 5V/20000mAh rechargeable Li battery pack (<US$50). The 12V/max 6A output is enough to power the little Yeeco amp at least as well as that little switching power supply that came with it. Notice this battery also features a USB 5V output. 9V output can be obtained using an included cable.
A couple more pictures of the little amp:
I initially got the blue one but noticed within a few days that the USB input was not working reliably so returned it and got the gold unit instead which you'll see in the images below. As one might expect with inexpensive devices like this, quality control might not be the best, but Amazon's return / replacement policy is generous.
Physically it looks good with the robust gold-plated speaker terminals that accept standard banana plugs. As usual, you can loosen the screws and there are holes for bare wires. The body is metal. The only potentially worrisome piece is the little plastic On/Off switch up front.
When turned on, the amp plays a little jingle and a female voice (of Asian accent) tells you which input is selected. There is no indicator otherwise except for a power LED and the input selection is automatic such as when you plug in a USB cable or pair it over Bluetooth. I have not used the Bluetooth much and the couple times I tried, I did not have any problems pairing the "F900S" to my Samsung Note 5 phone - while lossy of course, it sounded reasonable with decent bass and treble extension.
The little amp is based on the TI TPA3116 Class D chip amplifier, released in 2012 and probably a product of TI's acquisition of Toccata in 2000. As you can see in the datasheet, the device is rated as 2-channel 50Wpc into 4-ohms using a 21V power source. The power specs are rated at 10% THD+N which is high (important to keep this in mind!). Given that I am using a 12V battery source instead of 21V, the power rating will be more like 20W into 4-ohms depending on how generously you accept the distortion value. So we're looking at about 10W into 8Ω. This still should be powerful enough for reasonably sensitive speakers. Remember the previous blog post about testing for oneself "How many watts do you really need?" We don't all need hundreds of watts for room-filling sound, in fact it looks like 70% of us can get by with a maximum of 25W into 8Ω or less. As expected, as a Class D amp, this thing barely gets warm after a couple of hours of playback at a good listening level.
Normally, my system looks like this with the two Emotiva XPA-1L 250W (rated into 8Ω 0.1% THD) monoblocks in front sitting on the floor. Notice the left amp has the top opened - I needed to replace the XLR connector as my cable was getting stuck and the locking mechanism wasn't letting go around the time I took this picture.
|RCA output from HiFiBerry DAC+ Pro feeding the Yeeco amp on the other side.|
|Little Yeeco amp, powered by TalentCell 12V battery, analogue input through front AUX cable, output to speakers.|
Another noticeable limitation was that one has to be careful to keep audio input level low. The HiFiBerry DAC+ Pro's analogue outputs can go slightly over 2Vrms. At this level, the Yeeco amp sounds like it's clipping at the peaks, resulting in a rather harsh sound. I'll need to check this out with measurements. Make sure to pull down the volume fed into the amp. I suspect it's best to drop it to about 1V peak. The TPA3116 can be set at various gain levels depending on resistors on the board, I assume it's one of the higher values being used here. I've heard that setting it to the lowest 20dB gain improves noise level significantly. Might be fun to open this up for a mod.
I agree with the other reviewer on TNT-Audio that bass is a bit leaner. But it's far from absent and at times I was a little surprised how full it still sounded. The treble was also quite nice, though missing a small amount of extra clarity up top while doing a quick A/B switch of amps. There is an "airiness" to the sound which suggests loss of resolution and for me can sound a bit thin at times, but works well for some music and adds to the atmosphere when appropriate. Remember that I'm just using a 12V battery here, so as suggested by the other review, perhaps bass power and clarity could be reinforced with more juice to the amp.
While it cannot reproduce the same level of bass "ooomph" with electronic music like Depeche Mode's Remixes 2: 81-11, the power output is enough to drive my speakers to appropriate listening levels in my room with the volume knob at 25-30% (the Paradigms are rated at 89dB/W/m anechoic, 92dB/W/m in-room sensitivity).
Female vocals sounded good. For example, Morgan James' Hunter was nice and punchy with good front-and-center vocal placement (mix of R&B, pop tracks). Even an inexpensive streamer/DAC/amp combination like this can create the nice illusion of "disappearing speakers".
I mentioned above the sense of "airiness". Well, some New Age albums like Enya's 2015 release Dark Sky Island sounded great through this little amp with lots of atmosphere. Likewise, small classical ensembles like Yo-Yo Ma, Chris Thile & Edgar Meyer's Bach: Trios (excellent 24/96 hi-res version available, released 2017) played back with credible handling of nuances, presenting the joyful interplay of cello, bass and mandolin with good instrument placement in the sound stage.
For poor masterings like the just-released Corey Hart Dreaming Time Again (DR5), while I can still enjoy the pop/rock mix and reminisce of the 80's, the recording quality leaves much to be desired. Lame, whimpy, altogether unsatisfying sound throughout the EP from all that terrible dynamic range compression. If only this was recorded to the dynamic range standards used in the 80's and early 90's, the music would have been so much more interesting and exciting (there are some enjoyable tracks here)!
It's rather sad and maddening that in 2019, the record companies don't seem to understand that the poor sound quality of these recordings are likely hurting sales and driving music fans away from artists and their music in general. Despite hi-fi technology improving over the years, the technical qualities of mainstream music have as a whole diminished...
Finally, for even more fun, let's try running this all with one battery source!
As discussed, I received the Topping D10 DAC a few weeks back which can be powered off the Raspberry Pi 3 (B+) streamer through USB, and since the TalentCell battery can output both 12V and 5V simultaneously, the whole thing can be wired up like this...
Raspberry Pi 3 streamer --> USB --> Topping D10 DAC --> RCA-to-phono --> Yeeco amp --> Speaker cables --> Paradigm Signature S8 speakersTalentCell battery feeding Raspberry Pi 3 (5V) and Yeeco amp (12V).
How does this sound? Not as good as with the separate batteries. Clearly the noise floor is elevated and I can hear a bit of buzzing interference which was not an issue using 2 separate batteries. Sounds like interference from the Raspberry Pi 3 + USB DAC creeping into the amp.
Anyhow, while the little Yeeco amp sounds decent even with these large speakers at 12V off a battery, this is the kind of amp meant for small passive systems you might have such as for computer speakers as long as you have no need for headphone out. They would be good for a little kitchen or maybe casual bedroom systems where you might want to send some Bluetooth audio to once awhile. In my opinion, despite good reviews and general sound quality, this is not "high fidelity". Definitely try running them with an old 19V laptop power supply for a bit more juice and presumably lower distortion at given power output. I'll report on the performance once I get the amplifier test bench up and running for measurements.
Remember that these days, there are many options with amps using little Class D chips like this. For example, I was tempted to try out this Douk Audio G3 Pro which features 2 of these TI TPA3116 chips (bridged mode for higher power, lower distortion), can do Bluetooth AptX plus headphone out but no USB DAC function.
You might be wondering why I'm showing you this... In part it's because every once awhile it's good to take the pulse of what's achievable with very few dollars! Down the road, I'll measure this little Yeeco amplifier to examine how well a little device like this performs objectively. Clearly, at <US$35 there is essentially little else "lower end" than something like this. Having an awareness of the objective performance of something in this price bracket can shed some perspective on "value" and expectations of level of performance for audiophiles.
Okay guys, I'm preparing to head off to Europe with the family for some vacation time. :-)
I see that the Raspberry Pi 4 has been released. Nice. With a true gigabit independent from the USB system, I suspect this will resolve the need to drop the ethernet down to 100Mbps I discussed with the Pi 3 B+ previously when upsampling to USB. Maybe I'll check this out after the vacation.
Hope you're all enjoying the music!