Nobsound NS-01G / NS-10G Amplifiers

These are tiny Bluetooth/USB/line amplifiers sold on Amazon. I supposed technically these are receivers since they have three possible inputs?

NS-01G, NS-10G, NS-10G with power supply

The specs on these are somewhat conflicting, either NS-01G uses the TPA3110 chip and the NS-10G uses the TPA3116 chip, or they both use the TPA3116. The TPA3116 was tested by Audio Science Review and they weren't too impressed by the noise floor in particular.

The amplifiers can be purchased with or without a power supply. The power supply that is provided by the manufacturer outputs 12 V which is only half of the working voltage of the amplifier chip (24 V). What this means is that, given a sufficiently strong input signal, these amplifiers hard clip at around half volume - the circuitry in them is expecting a 24 V supply, once the output signal reaches 12 V it just flatlines there. This is a great example of how a low power amplifier can destroy speaker drivers due to clipping - these amplifiers hard clip at very tolerable SPL levels.

An easy upgrade for these amplifiers is to power them with a laptop power supply, which normally output about 19.5 VDC. This voltage probably derives from Lithium battery chemistry and is the same for all major laptop manufacturers (Dell, HP, Lenovo) for many years of laptop models. The "tiny" form factor desktop PCs from these manufacturers use identical power supplies too. In my case I decided to recycle a buzzing Lenovo power supply for an old Thinkpad that, due to the buzzing, I find unusable for its primary application of powering a laptop.

You can cut and replace the plug on these - the amplifiers take a "standard" power brick plug (i.e. the one found in vast majority of electronics that takes at least 12 VDC as input). I removed the female power socket from a dead Thinkpad and wired it to a small board with a LED indicating power. I also installed audio clipping indicators on this same board - LEDs that light up when there is approximately 35 V peak-to-peak on the AC output of the amplifier.

With the 20 V power supply, the amplifier is capable of respectable SPLs without hard clipping. I wouldn't say without distortion because, based on the ASR review, they do distort quite a bit.

This performance though is only possible over short cables. I tried running 50' of 18 gauge copper cable between the amplifier (NS-01G) and each speaker, and the result was 1) lots of TV static-like noise when the amplifier was turned on and nothing was playing, 2) audio signal cutting in and out at low volume, 3) audio signal being obviously distorted at higher volumes. The combination was unusable. This was on the 20 V power supply.

I replaced the NS-01G with Niles TVA50 and the static noise was immediatly gone and reasonable sound quality returned. I wasn't quite getting the fidelity of my reference systems, but given the 50' of 18 gauge wire this probably should be expected.

The power ratings of these "no-name" Chinese amps are, essentially, fraudulent. They take the chip power ratings which are given at 10% THD into a 4 ohm load at maximum permitted supply voltage and advertise this as the power rating for the amplifier even if they include a power supply that outputs half of the maximum voltage accepted by the chip.