This is a review and detailed measurements of the xDuoo TA-20 hybrid transistor and tube balanced headphone amplifier. It was kindly sent by member @xtenik who is a distributor for xDuoo products. The TA-20 costs US $399.
I previously reviewed the xDuoo TA-10 and was impressed by the quality of the DAC implementation. The tube amplifier stage had a lot of distortion of course but subjectively it sounded good. That, and solid build led me to recommend the TA-10. Some people however asked for the balanced version of that unit. Turns out that doesn't exist. The TA-20 for some reason eliminates the DAC which was the bell in that ball.
The TA-20 has the same nice build quality of the TA-10:
The two tube guards are magnetic and snap nicely into their sockets. They make you want to keep taking them out and reattaching them. The volume control feels good. It is a rotary encoder and linearity changes values as you turn the volume.
Naturally you have both 1/4 headphone jack and XLR for "balanced" headphones.
The back panel shows three inputs which is nice:
For my testing, I only used the XLR inputs.
Inclusion of mains power supply is a great touch to reduce clutter on or around your desk.
In use the tubes barely get warm. The real work is performed with solid state transistors in the output stage. This has the advantage of lower output impedance than a tube transformer-less design would deliver.
The unit came with stock Chinese 12AU7 tubes:
Headphone Amplifier Measurements
I connected my analyzer output to XLR inputs set to 4 volts and volume adjusted for the same 4 volt output (unity gain) and this is what I got:
We see some channel imbalance as indicated by the sine wave graphs and RMS levels.
Distortion is sky high but it is mostly in the form of second harmonic as is often promised, but not always delivered with tube amplifiers.
SINAD is the combination of noise and distortion relative to our 1 kHz signal and suffers greatly due to high distortion:
Signal to noise ratio is actually good, clearing the 16 bit mark that is 99% of the music you listen to:
Measured at much lower level of 50 millivolts though (right), performance drops severely:
That is probably due to the mains hum that is indicated in the FFT spectrum. So I would avoid the TA-20 with sensitive IEMs/headphones.
Frequency response was very wide and flat but not without problems:
The channel in red is clearly having some stability issues in addition to being at a different level than the other. The latter may cause a subtle shift in soundstage which some may take for an improvement. It is not.
Intermodulation and noise versus input level shows copious amount of non-linearities:
Running the same test but examining the THD+N gives us:
So the optimal input is about 0.1 volt. And the unit starts to clip at a little above 3 volts. So our dashboard at 4 volts input is showing more of a worst case situation than other input levels would indicate. But not much.
THD+N versus power at 300 ohms gives us what we can predict:
Lots and lots of distortion but also tons of power. My criteria here is 100 millwatts and the TA-20 busts pass that with 326 milliwatts. As result the TA-20 should have no trouble driving high impedance headphones to deafening levels.
Going to the other extreme of 33 ohm, we get a similar picture:
Testing for balanced power, I tested the TA-20 both with its 1/4 Headphone jack and XLR:
The XLR output (don't confuse with input) produces much lower noise which was nice. It also has less distortion at the limit. As such, if you have a choice, definitely use the XLR "balanced" output. You get more power, less noise and distortion.
Output impedance was 4.5 ohms which can cause frequency response of low impedance headphones to change (for better or worse):
For kicks, I also measured that versus frequency:
The impedance is more or less frequency independent which is good.
There must be some kind of digitally controlled gain stage for the volume control as it had perfect channel matching:
Headphone Listening Tests
I did not have time for controlled testing so these are subjective listening tests of moderate value.
I started with my Drop Ether CX 25 ohm impedance using XLR output of the TA-20. These are very inefficient headphones and require good bit of current to produce high SPL (loudness). The TA-20 had no trouble driving them as hard as I would dare. Overall dynamics was very good but I thought the highest were a bit exaggerated and vocals a bit lispy.
I then switched to my Sennheiser HD-650 using 1/4 headphone out. I had no trouble waking up the neighbors with the TA-20! There seemed to be infinite amount of power here and produced very satisfying sound which I could not fault. Even at maximum volume, the combination was dead quiet.
I detected no "tube magic" though. Soundstage didn't' change. Digital did not become analog. Angels did not lift me and take me to a sunny beach either. I just heard good sounding music as I do with other headphone amps of similar power.
All of this may change in a controlled AB test but being lazy and out of time, that is all I have for you.
Conclusions
The measured performance of the xDuoo TA-20 gets a failing grade as one could predict. The build quality, digital volume control and powerful amplifier stage substantially change the final calculus. The cost is high though at $399 especially since you have to add a DAC to it as well.
Overall, I can't recommend the TA-20 but you have all the data to judge for yourself.
--------
As always, questions, comments, corrections, etc. are welcome.
One of the panthers is complaining that he is getting too old to see in the dark and wants night vision scope for night time hunting! I checked and these things are expensive. So I appreciate some donations to get him one for Christmas using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
I previously reviewed the xDuoo TA-10 and was impressed by the quality of the DAC implementation. The tube amplifier stage had a lot of distortion of course but subjectively it sounded good. That, and solid build led me to recommend the TA-10. Some people however asked for the balanced version of that unit. Turns out that doesn't exist. The TA-20 for some reason eliminates the DAC which was the bell in that ball.
The TA-20 has the same nice build quality of the TA-10:
The two tube guards are magnetic and snap nicely into their sockets. They make you want to keep taking them out and reattaching them. The volume control feels good. It is a rotary encoder and linearity changes values as you turn the volume.
Naturally you have both 1/4 headphone jack and XLR for "balanced" headphones.
The back panel shows three inputs which is nice:
For my testing, I only used the XLR inputs.
Inclusion of mains power supply is a great touch to reduce clutter on or around your desk.
In use the tubes barely get warm. The real work is performed with solid state transistors in the output stage. This has the advantage of lower output impedance than a tube transformer-less design would deliver.
The unit came with stock Chinese 12AU7 tubes:
Headphone Amplifier Measurements
I connected my analyzer output to XLR inputs set to 4 volts and volume adjusted for the same 4 volt output (unity gain) and this is what I got:
We see some channel imbalance as indicated by the sine wave graphs and RMS levels.
Distortion is sky high but it is mostly in the form of second harmonic as is often promised, but not always delivered with tube amplifiers.
SINAD is the combination of noise and distortion relative to our 1 kHz signal and suffers greatly due to high distortion:
Signal to noise ratio is actually good, clearing the 16 bit mark that is 99% of the music you listen to:
Measured at much lower level of 50 millivolts though (right), performance drops severely:
That is probably due to the mains hum that is indicated in the FFT spectrum. So I would avoid the TA-20 with sensitive IEMs/headphones.
Frequency response was very wide and flat but not without problems:
The channel in red is clearly having some stability issues in addition to being at a different level than the other. The latter may cause a subtle shift in soundstage which some may take for an improvement. It is not.
Intermodulation and noise versus input level shows copious amount of non-linearities:
Running the same test but examining the THD+N gives us:
So the optimal input is about 0.1 volt. And the unit starts to clip at a little above 3 volts. So our dashboard at 4 volts input is showing more of a worst case situation than other input levels would indicate. But not much.
THD+N versus power at 300 ohms gives us what we can predict:
Lots and lots of distortion but also tons of power. My criteria here is 100 millwatts and the TA-20 busts pass that with 326 milliwatts. As result the TA-20 should have no trouble driving high impedance headphones to deafening levels.
Going to the other extreme of 33 ohm, we get a similar picture:
Testing for balanced power, I tested the TA-20 both with its 1/4 Headphone jack and XLR:
The XLR output (don't confuse with input) produces much lower noise which was nice. It also has less distortion at the limit. As such, if you have a choice, definitely use the XLR "balanced" output. You get more power, less noise and distortion.
Output impedance was 4.5 ohms which can cause frequency response of low impedance headphones to change (for better or worse):
For kicks, I also measured that versus frequency:
The impedance is more or less frequency independent which is good.
There must be some kind of digitally controlled gain stage for the volume control as it had perfect channel matching:
Headphone Listening Tests
I did not have time for controlled testing so these are subjective listening tests of moderate value.
I started with my Drop Ether CX 25 ohm impedance using XLR output of the TA-20. These are very inefficient headphones and require good bit of current to produce high SPL (loudness). The TA-20 had no trouble driving them as hard as I would dare. Overall dynamics was very good but I thought the highest were a bit exaggerated and vocals a bit lispy.
I then switched to my Sennheiser HD-650 using 1/4 headphone out. I had no trouble waking up the neighbors with the TA-20! There seemed to be infinite amount of power here and produced very satisfying sound which I could not fault. Even at maximum volume, the combination was dead quiet.
I detected no "tube magic" though. Soundstage didn't' change. Digital did not become analog. Angels did not lift me and take me to a sunny beach either. I just heard good sounding music as I do with other headphone amps of similar power.
All of this may change in a controlled AB test but being lazy and out of time, that is all I have for you.
Conclusions
The measured performance of the xDuoo TA-20 gets a failing grade as one could predict. The build quality, digital volume control and powerful amplifier stage substantially change the final calculus. The cost is high though at $399 especially since you have to add a DAC to it as well.
Overall, I can't recommend the TA-20 but you have all the data to judge for yourself.
--------
As always, questions, comments, corrections, etc. are welcome.
One of the panthers is complaining that he is getting too old to see in the dark and wants night vision scope for night time hunting! I checked and these things are expensive. So I appreciate some donations to get him one for Christmas using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/