Reisong A10 Amazon Link
China HIFI Audio Link
I recently purchased a Reisong A10 amp from Amazon. This is a low powered Single Ended Triode (SET) Tube Amplifier. I wanted to give tubes a try and this seemed like a good starting point. As you will see by the measurements below, this amplifier does NOT measure well at all, even for a Single Ended Tube amplifier, the distortion measurements are high.
However, while I know that this site focus is measurements, I will have to say that the amplifier sounds significantly different then the Class D, Class A and Class AB solid state amps I have here. It sounds closest to the Pass clone Aelph 3 amplifier I also have and previously measured. The tube amplifier is low powered so sensitive speakers 89db or better is advised. Turning the volume up 75% on the knob makes my 89db sensitive speakers very loud in my medium sized room. The tube amplifier adds a certain richness to vocal and acoustical music that gives a "you are there" feeling making music sound live.
Clone Aelph 3 measurements
With the descriptive prelimiary comments out of the way, lets move on to the real reason we are here, the measurements. Interested readers can review my DIY test setup and equipment here:
DIY test setup (Panasonic XR57 example)
One additional test setup note, I am mostly measuring only one channel. However tube amps don't like to be turned on with out a speaker load on the output taps. So I have a dummy 4 ohm load on both the channel I am measuring as well as a separate one on the channel unused.
Below is the REW EQ measured frequency response with the volume set to 50% (approximately .78watts into 4 ohm). Note the high frequency drop off (that is characteristic of all EL34 SET amps or just this one?):
Below is the measurement of a 1khz source, 4ohm load, 30% volume control setting, .51vrms (approximately .04w). Note that we are at 1% distortion already at this volume level. You will note a significatant 60Hz power spike. I did try to make some measurements with my REW EQ laptop on battery power and the 1khz source DAC connected via TOSLINK optical. That setup did not reduce the 60hz spike. The DAC was 3 prong (grounded outlet) electrically powered on the same power strip as the 3 prong Reisong A10 amplifier.
Below is the measurement of a 1khz source, 4ohm load, 50% volume control setting, 1.77vrms (approximately .78w). This is the max level I typically listen at in my room with my bookshelf speakers (89db sensitivity):
Below is the measurement of a 1khz source, 4ohm load, 70% volume control setting, 2.67vrms (approximately 1.78w):
Below is the measurement of a two tone 19K and 20K source, 4ohm load, 70% volume control setting:
Again, the measurements here have a disappointingly high amount of distoration even at low 1-2 watt outputs. SET amps are famous for mostly 2nd harmonic distortion that is said to give the amp a "warm" sound. But this amp (although progressively less at higher harmonics) has high levels of distortion. The amp measures poorly but qualitatively has a very pleasing sound to listen too. All measurements taken with the factory default tubes.
Comments welcomed on my findings and test setup. I am open to trying other measurements to better characterize my new tube amplifier.