Through a wrinkle in the China-US postal system, I recently ended up with two new amplifiers: a Nobsound TPA3116 dual-chip (100W/channel) and an FX Audio FX502SPRO TPA3250, both from ebay seller doukmall. I also have a Yuan-Jing TPA3116 single-chip board purchased two years ago from Parts Express and packaged in a cigar box. So, I thought I would do a little review and comparison.
For the most part, I am listening to these on a desktop system: lossless CDs on a Synology NAS -> MacBook Air USB -> Schiit Modi 2 Uber DAC -> amplifier -> Q Acoustics 3010 speakers (86dB, 6ohm). I have three laptop-style power adapters for the amplifiers: a 12V 5A, 19V 6.3A, and 24V 4A (which came with the FX Audio). The difference among the power supplies is subtle, but I think all the amplifiers sound slightly better with the 19V 6A supply. It may be confirmation bias, but I think the bass is slightly fuller and distortion becomes noticeable at a slightly higher volume.
Nobsound TPA3116 first impressions. Compared to my cigar-box YJ TPA3116, the Nobsound delivers much more bass. It also gets loud very quickly. A little sound comes out at 0 on the dial, 1/8 turn is where sound gets audible, and 1/4 turn is pretty loud. The amplifier sounds fine, but it produces a lot of hiss/hum that increases with higher volume. You can't really hear this when music is playing, but it's apparent when there's no signal past about 1/2 way on the dial.
Overall, the sound is very good. It sounds clear and detailed. The high treble range seems a little "hot" and can sound harsh at higher volumes. At normal listening levels this is not an issue. This is a very nice amplifier, but I think I see how it could be improved through the gain modification mentioned on this forum.
I also listened to the Nobsound on larger speakers: Synology NAS -> Airport Express -> Nobsound TPA3116 amplifier -> Wharfedale Diamond 10.7 speakers (floor standing, 90dB, 6ohm). This setup seemed to confirm my initial impressions. The amplifier sounds clean and has strong bass at lower listening levels. It gets loud very fast, and on these speakers I could not turn the knob much past 1/4 without it getting uncomfortable. The treble harshness is even more pronounced, and at higher volumes this is annoying. Compared to my 20 year old Harman Kardon AVR40, the Nobsound sounds cleaner and more precise with very little (if anything) lacking in the low end.
FX Audio TPA3250 first impressions. The FX Audio TPA3250 sounds quite good. I think it is the best amplifier of the pack. At 0 on the dial there is no sound output to the speakers. Sound becomes audible around 1/8th turn, a little loud around 1/4 turn, and very loud around 1/2 way. I don't detect noticeable distortion until at least 5/8 of the way around, and I would never listen to music that loud. The volume knob is stepped, but I don't think the potentiometer is--I think it's a regular potentiometer with a stepped dial. I can hear a slight hiss near maximum volume with no source playing, but it's a lot less than on the Nobsound TPA3116. This amplifier sounds clear and detailed. I don't detect any range of frequencies dominating or becoming harsh. The volume can go very loud and not sound distorted.
I was very impressed with this amplifier connected to the Wharfedale speakers. There is good bass, lots of detail, and the volume gets very loud with everything sounding very clear. I could not turn the volume up enough to hear noticeable distortion.
Comparing the Nobsound TPA3116 and the FX Audio TPA3250. Although these amplifiers have probably not had enough running time to "break in", my initial impressions are that the FX Audio is a good deal better than the Nobsound. Both sound better than the YJ TPA3116. However, the Nobsound sounds a little "hot"--the volume gets too high too quickly, the distortion kicks in fairly early, and the treble range sounds harsh at higher volumes. The FX Audio gets very loud as well, but can go much louder before distortion kicks in. The FX Audio appears to have better bass and overall is better balanced across all frequencies and more pleasurable to listen to.
Driving large floor standing speakers, again the FX Audio is preferred over the Nobsound. Both amplifiers sound good at normal listening levels, but the FX Audio is better balanced and sounds very good at higher volumes. In fact, I have left the FX Audio connected to my main system, displacing the 20 year old Harman Kardon, at least for now. This leaves me with the Nobsound on my desktop setup, and it sounds fine, just not quite as good as the FX Audio.