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Reisong A10 EL34 Hi-Fi Audio Stereo Tube Amplifier Single-end Class - A Review

dumpingg

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Reisong test setup.JPG


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?):

Reisong A10 Frequency Response 4ohm load 50% volume warmed up.png

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.

Reisong A10 with toslink dac 1khz source 4ohm .51v 30% volume factory tubes.png


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):

Reisong A10 with toslink dac 1khz source 4ohm 1.77v 50% volume warmed up factory tubes.png


Below is the measurement of a 1khz source, 4ohm load, 70% volume control setting, 2.67vrms (approximately 1.78w):

Reisong A10 with toslink dac 1khz source 4ohm 2.67v 70% volume warmed up factory tubes.png


Below is the measurement of a two tone 19K and 20K source, 4ohm load, 70% volume control setting:

Reisong A10 70% volume 4 ohm 19 and 20k tones factory tubes.png


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.

P1110969_DXO.jpg


P1110963_DXO.jpg
 
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D

dumpingg

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There is one question I have about my setup. The Reisong A10 says that it's input sensitivity is 750mv. My DAC at max volume is spec'ed at a more normal 2Vrms. So it is possible that I am driving the input of the Reisong too hot and causing distortion in my test setup? How would I check for something like that?
 

TheGM

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View attachment 109683

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?):

View attachment 109685
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.

View attachment 109686

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):

View attachment 109687

Below is the measurement of a 1khz source, 4ohm load, 70% volume control setting, 2.67vrms (approximately 1.78w):

View attachment 109688

Below is the measurement of a two tone 19K and 20K source, 4ohm load, 70% volume control setting:

View attachment 109689

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.

View attachment 109695

View attachment 109696

Thanks for the specs, nicely presented! Kind of funny to find this post today. I ordered and received this 'little guy' about a month ago. I've been working my way through some of the MANY low-priced Chinese tube amps over the last couple of years. Having spent a small fortune in the past on some 'high end' tube audio, I wanted to see what could be done at this price point. And frankly, I was impressed by this one. I tried a Musical Paradise MP-301 last year, but sent it back due to high noise levels. Now, to be fair, being a 'tube guy', I never even tested this with stock tubes. I had my own burned in to choose from. I'm currently running Genelex EL-34's (new Russian version) and some NOS RCA12AX7's (using a slight circuit mod to replace the 6N2p). Very smooth and surprisingly quiet. I'm going to keep this one for a small office or den setup I think.
 

Vini darko

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Certainly puts the gushing on you tube into perspective. Thanks for doing and posting measurments.
Looking at the underside it's hardly surprising it has so much distortion. Don't see any feedback or much of anything :D
About as basic as an amplifier can be. I quite like that in truth. Though wouldn't spend my own money for it.
 
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dumpingg

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Thanks for the specs, nicely presented! Kind of funny to find this post today. I ordered and received this 'little guy' about a month ago. I've been working my way through some of the MANY low-priced Chinese tube amps over the last couple of years. Having spent a small fortune in the past on some 'high end' tube audio, I wanted to see what could be done at this price point. And frankly, I was impressed by this one. I tried a Musical Paradise MP-301 last year, but sent it back due to high noise levels. Now, to be fair, being a 'tube guy', I never even tested this with stock tubes. I had my own burned in to choose from. I'm currently running Genelex EL-34's (new Russian version) and some NOS RCA12AX7's (using a slight circuit mod to replace the 6N2p). Very smooth and surprisingly quiet. I'm going to keep this one for a small office or den setup I think.

thanks for the comments. I also have a selection of alternate tubes that I will trying and measuring. I will post those results when I have them ready.

For the 12AX7 pre-amp tubes, did you use an adapter or did you rewire the pin's directly on the A10? What adapter did you use?
 

JeffS7444

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Nice amp! Hum aside, I suspect it's designers accomplished exactly what they intended to do, which was to deliver plenty of tube "juice". I also see that Soviet 6N2P-EV tubes are available cheaply, where the "-EV" generally indicates extended-life. Did you have a chance to measure 1 kHz square waves? They can reveal misbehavior well beyond 20 kHz.
 

DSJR

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I still get torn between a 'sorted' kind of amp with loads of components in and especially around the signal path doing loads of 'house-keeping' for want of a better description and something as utterly simple as this with seemingly hardly anything at all in the signal path except the valves (two a side?) and the output transformer...
 

Helicopter

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Awesome review. Thanks so much for sharing. I would love to do similar work if I had the time, and I have been interested in this particular model as well. I have a Shuguang SG-845-7 that also has a 60Hz buzz, but I think that is one of the pairs of tubes I am running for the most part. These devices are so pretty and elegant.
 

steve-z

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Would also like to add that I don't get any hum either from the amp directly or from the speakers at any volume, I would also state that I noted that the A10s supplied power cable was of very low quality so I left it in the box, I use a cable constructed by myself from high quality Belden shielded mains cable and high quality plugs to give the amp it's best chance of performing optimally.
 

Helicopter

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I don't remember having hum when my SET amp was new, but i have it now. my guess is it is caused by the tubes in my case, and that tubes are a common source of hum in a tube amp.
 

steve-z

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There is one question I have about my setup. The Reisong A10 says that it's input sensitivity is 750mv. My DAC at max volume is spec'ed at a more normal 2Vrms. So it is possible that I am driving the input of the Reisong too hot and causing distortion in my test setup? How would I check for something like that?
Although your DAC and CD players too have a rated output of 2volts, you only get 2volts if the input digital signal is recorded right up to 0db, if the signal was recorded with a maximum level of -5db then the output from the DAC or CD player would be less than 750mv, a lot of my 70's and 80's albums are a lot lower than that, in fact within the itunes settings on my iMac you can boost the level by up to 100%, I've boosted most of my older recordings by 40-60% to get parity with newer recording.
 
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dumpingg

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I have spent some additional time measuring and tube rolling. The measurements below cannot be directly compared to my previous. I deleted the toslink DAC and just used my Focusrite USB Scarlett 2i2 for both input (measurement)/output (source). This change in measurement setup (deleting the TOSLINK DAC has changed the noise floor a bit between the original and these measurements).

Here are the tubes I have rolled:

Voskhod Rocket 6N2P-EV to replace stock factory Pre tubes.
Tung-Sol EL34B and Genalex KT77 Golden Lion to swap out for the factory PSVane EL34 power tubes.

Here is the frequency sweep for the different tube combinations, note the 1db increased response 20-6khz for the KT77 tubes vs the others.

Reisong A10 Tube Rolling Freq Sweep.png


Here is the remeasured factory tubes (pre and power), 4ohm, 50% volume :

Reisong A10 4ohm 50% volume 1khz source FACTORY TUBES RIGHT.png


Here is the measurement for Voskhod Rocket 6N2P-EV pre and factory PSVane EL34 power tubes:

Reisong A10 4ohm 50% volume 1khz source RIGHT Factory plus rocket 6N2P_EV pre tubes.png


Here is the measurement for the Voskhod 6N2P-EV (pre) and Tung-Sol EL34B (power) tubes, note that the 60Hz power spike is reduced:

Reisong A10 50% volume 4ohm 1khz Voskhod Rocket 6N2P-EV - TungSOL EL34 tubes.png



Here is the measurement for the Voskhod 6N2P-EV (pre) and Genalex KT77 Golden Lion (power) tubes, note the noise floor seems to have increased:

Reisong A10 50% volume 4ohm 1khz Voskhod Rocket 6N2P-EV Golden Lion KT77.png
 

DSJR

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Fascinating thread for me at least :D

Delving back into my ancient history, I remember being told that a little bit of wideband noise never did domestic listening - for pleasure - any harm if it wasn't excessive and FM radio at its best was a classic example back in the days when the BBC really cared about the sonic qualities of it's output and did some superb live broadasts. Can't remember the exact figures, but UK FM radio was more like 65 to 70dB S/N I seem to remember.
 

steve-z

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I assume as well as testing the different tube combinations you also have done some comparison listening tests, I wonder if you have a definitive favourite or is it too close to call .
 
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dumpingg

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I am still comparing and listening the tubes. I will say that the KT77 plays louder and has a stronger presence and body to it. But as you can see in the measurements it comes at the expense of furthering the fall off effect of the top frequencies on the A10.

If I had to pick a winner I would say the rocket pre tubes plus the tongsol EL34 tubes.
 

steve-z

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I am still comparing and listening the tubes. I will say that the KT77 plays louder and has a stronger presence and body to it. But as you can see in the measurements it comes at the expense of furthering the fall off effect of the top frequencies on the A10.

If I had to pick a winner I would say the rocket pre tubes plus the tongsol EL34 tubes.
I don't find the rolloff at high frequencies to be too much of a problem and when all's said and done it's only abut 2db down at 10khz and with a lot of current music having a boost at high frequencies I find it's a good thing that the A10 sweetens the top a little. Both my sources, itunes on my iMac and the 4Stream app controlling my Arylic S10 streamer both have adjustable EQ so a bit of subtle treble lift can be applied if needed.
 

steve-z

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Took the opportunity to do a little tube rolling on my A10, bought a pair of Voshkod Rocket pre tubes, they've been installed for 3 days now and I'm pleased with the improvements, the upper mid and treble have now become a little more brightly lit which has obviated the need for the small amount of EQ lift in the treble I've been using to offset the slight rolloff with the stock Chinese tubes, well worth the change for £20.
 
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