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Topping A50s Headphone Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Topping A50s. It was kindly sent to me by the company for testing. The A50s is already available in limited quantities and costs US $199.99.

Despite being small the A50 is rather heavy and sturdy which bodes well for staying on the desk:

Topping A50s Headphone Amplifier stereo review.jpg


There is a standard 1/4 headphone socket and a balanced 4.4 mm. Two gain settings are provided: 0 dB (pass through) and 6 dB. The power button cycles through the gain settings.

Even though there are "balanced" outputs, input is limited to RCA unbalanced input:

Topping A50s Headphone Amplifier back panel RCA Power Supply stereo review.jpg


Power is provided by an external 15 volt, 1 amp switching power supply as you see in the picture above.

Headphone Amplifier Measurements
As always we start with our dashboard feeding the unit 2 volts and asking for 2 volts out:

Topping A50s Headphone Amplifier Audio Measurements.png


Distortion is stunningly low at -145 dB, approaching the limit of the analog generator in my Audio Precision analyzer. SINAD which takes into account noise is limited by noise of the amplifier and analyzer and clocks at a wonderful 121 dB:
Best headphone amplifier review.png


We can examine signal to noise ratio by itself:

Topping A50s Headphone Amplifier Dynamic Range Audio Measurements.png


Even at highly reduced output level of 50 millivolt, noise is very well controlled, providing 16 bits of dynamic range:

Lowest Noise Headphone Amplifier Review Measured.png


Frequency response is flat of course to beyond 100 kHz:

Topping A50s Headphone Amplifier Frequency Response Audio Measurements.png


Power is most important in a headphone amp as if you run out of that, distortion sets it and in a very nasty way. So let's see how much juice the A50s can provide using a high 300 ohm load:

Topping A50s Headphone Amplifier Power into 300 ohm Audio Measurements.png


It was just yesterday that we were gushing about the Drop THX 789. See how the A50s leaves it in the dust as far as noise not only in low gain but also high gain! Output power is 52 milliwatts in high gain mode. This is due to modest 6 dB gain. If you have a balanced DAC, you can feed it higher voltage than the 2 volts I used to get more power. Alternatively, you can use the 4.4 mm headphone jack:

Topping A50s Headphone Amplifier Power into Balanced 300 ohm Audio Measurements.png


Now you well exceed my threshold of 100 milliwatts and keep noise and distortion absolutely in check.

Using the same balanced output, let's go down to 50 ohm which forces the amplifier to produce more current:

Topping A50s Headphone Amplifier Power into Balanced 50 ohm Audio Measurements.png


Nearly 3 watts of power out of this little amp! Note that the above sweep goes to 4 volts which would represent using a balanced DAC with XLR to RCA out (or if it produces that much output using its RCA Out).

Using unbalanced out and 2 volt max sweep give us:

Topping A50s Headphone Amplifier Power into 33 ohm Audio Measurements.png


Finally, channel balance is quite good:

Topping A50s Headphone Amplifier Channel Difference Audio Measurements.png


As noted though, there are sample variations in the potentiometer so your results may not be as good. Fortunately the 0 dB low gain should let the volume control operate in its more linear region.

Headphone Amplifier Listening Tests
As always I start with my inefficient and low impedance Ether CX headphone. The A50s had no trouble handling it with unbalanced 1/4 out. For grins though, I switched to balanced output from it and now we are talking! Incredible and tight bass followed which is evidence of high power with exceptionally low distortion.

I switched to Sennheiser HD-650 using 1/4 out (too lazy to dig up my balanced cable). Power here was just enough to slightly resonate my ear lobes. :) If you wanted to have more enjoyment at the cost of reducing your hearing lifetime, you may want to use a balanced capable with it. That will give you 4X the power which should be plenty to drive the headphones themselves to distortion.

Conclusions
What can I say? We have another instrument-grade audio product in the form of A50s. You may be getting tired of seeing such exceptional results but I won't. It puts a smile on my face every time an audio product pegs my analyzer to its limits. Whether it is objective testing or subjective, the A50s nails the target of producing state of the art performance.

Needless to say, it is my pleasure to highly recommend the Topping A50s.

------------
As always, questions, comments, recommendations, etc. are welcome.

So another day goes by and we are still canning pears. 15 quart jars done yet we still have not made a dent in the harvest. I was going to ask my wife to help me carry a large speaker for testing but once I saw how tired she was after skinning 100+ pears, I decided it would be unwise. This is when I thought I should ask you all to donate enough money so I can hire someone to help us with this massive harvest. That way I can test more audio gear. Assuming you agree, here is the link: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

xarkkon

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May 26, 2019
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#6
Results are pretty much expected given how Topping has performed around with their products. My only issue with them is a million and one iterations of headphone amps with line/pre outs, but so so few all-in-one desktop amps for headphones and passive bookshelves. My SMSL AD18 has been holding up pretty well, but am waiting for some improvements to these product types. Topping, please deliver! :D
 

YSC

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#13
un-complainable performance as always, but I just did a quick search and found the original A50 used a chip volume control, any reason why opt for potentiometer this time round?
 

Veri

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#15
Nearly 3 watts of power out of this little amp! Note that the above sweep goes to 4 volts which would represent using a balanced DAC with XLR to RCA out (or if it produces that much output using its RCA Out).
Note that XLR to RCA will never yield full 4V output unless you are using a 1:1 transformer or some kind of universal buffer that would carry over the full voltage to one pin. The XLR's hot and cold signal can't cross over to the one-pin RCA standard over a cable or an adapter.
 
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