This is a review and detailed measurements of the Topping A70 Pro balanced headphone amplifier and preamplifier. It was sent to me by the company and costs US $499.
Like its companion DAC, the D70 Pro Sabre, the A70 Pro sports the gorgeous and highly responsive display (which can be set to above or graphic VU and spectrum analyzer). While it was nice to have in the DAC, it is essential here given the extensive functionality of this amplifier. Every input and output is selectable independently and in combination. If you need more inputs, you can get the optional Ext90 extension using the compatible connector:
Nice to see trigger in/out fully standard on Topping products.
Volume control is implemented using stepped relay to provide perfect channel matching. Normally this functionality comes at a cost of slow volume control response and noise induced into the audio path. Not here. Volume control could not be more responsive with very wide range of 100 dB. While you hear the mechanical relays if you get close to the unit, I could not detect any interruption or noise in the audio path. This is a superb implementation!
Microprocessor controlled protection circuit watches over the conditions of the device and shuts it down in extreme condition. What I like about it is that it auto recovers quickly and without user intervention. Firmware input support is provided for future refinement of this functional if needed.
Note that the extensive functionality makes the device a bit harder to use. You can easily get yourself in modes where you are not getting sound and wondering why. In this case, the level display is super helpful. As is the remote which automates some settings such as gain and RCA vs XLR input. You can also create two provides and recall them using C1 and C2 switches.
There is a ton of functionality here that would take me days to test. So I made a choice to make abbreviated preamp tests and then balanced headphone output.
Topping A70 Pro Preamplifier Measurements
Let's start with balanced input and output with variable volume control:
FFT display shows no recognizable distortion spikes other than the signal generator out of my audio analyzer! We are basically bound by signal to noise ratio which sets the overall SINAD to 121 dB (6 dB better than transparency under all conditions). Switching to RCA in/out surprisingly upped the performance a bit:
Balanced mode does provide more output though:
Finally here is our SNR:
Headphone performance should be highly indicative of preamp so let's get into that.
Topping A70 Pro Headphone Amplifier Measurements
As noted, I limited my tests to XLR balanced headphone output. Let's pump 4 volts into it and adjust volume to get 4 volts out:
We get the same great performance as we did in pre-amp mode. RCA input this time did cost us a bit as it normally does:
These are superb measurements, albeit just a hair off from best there is due to lack of an ultra low gain mode that some other Topping products have:
Noise performance shows why XLR input is a bit better:
50 mv output mode delivers near top of the class performance:
Frequency response is exceptionally flat:
Multitone performance is superb:
Power is just about everything in headphone amplifiers so let's see how we do there:
Wow, we have over 8 watts driving dual channels simultaneously at 32 ohm! Even low gain with its superbly low noise delivers 2 watts.
Changing the load from 600 ohm down to punishing 12 ohm shows superb ability to hold up the output voltage and hence keep delivering more and more power:
This is in entirely different class than any headphone amplifier I have tested!
I usually don't run the channel matching test with R2R relay volume controls but ran it here to show the superb implementation:
The dashed blue line shows deviation between the two channels. As you see, all the way down to the limit of -100 dB it remains at 0. Absolutely great!
Topping A70 Pro Headphone Listening Tests
I started testing my with everyday, low impedance and difficult to drive Dan Clark Stealth headphone. Even in low gain the A70 Pro drove these to almost ear bleeding levels and superb dynamics. Switching to high gains provided essentially infinite headroom and extra volume. Try as I might, I could not dare going past -15 dB. With other headphone amps, I could hear distortion at the maximum volume (or not enough volume). Both of those limits are long, long gone with the A70 Pro. You have so much power that any distortion or problems are clearly that of the headphone.
Switching for Sennheiser HD650 once again showed the incredible power reserves of the A70 Pro, allowing these headphones to shine with incredible detail and dynamics. There was no hint of any background noise and as noted, volume control was smooth, responsive and delight to adjust.
Conclusions
With A70 Pro, Topping pushes boundaries on multiple fronts. The device is gorgeous to look at, and informative and highly responsive to use. Power is increased to where it needs to be to drive even the most difficult to drive headphone as if it is a walk in the park. Measured performance is state of the art providing assurance of transparency. Subjective testing results couldn't be better. For a person who pushes amps to their max to see and hear the limits, I was out of a job with A70 Pro! There is not a negative here of any sort or shape. Yes, $499 is the price to pay. I suggest saving up money until you can afford to buy one if you are a serious headphone listener.
It is my pleasure to recommend the Topping A70 Pro. I am not sure how anything better can be designed but I am sure Topping will keep working at it!
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Like its companion DAC, the D70 Pro Sabre, the A70 Pro sports the gorgeous and highly responsive display (which can be set to above or graphic VU and spectrum analyzer). While it was nice to have in the DAC, it is essential here given the extensive functionality of this amplifier. Every input and output is selectable independently and in combination. If you need more inputs, you can get the optional Ext90 extension using the compatible connector:
Nice to see trigger in/out fully standard on Topping products.
Volume control is implemented using stepped relay to provide perfect channel matching. Normally this functionality comes at a cost of slow volume control response and noise induced into the audio path. Not here. Volume control could not be more responsive with very wide range of 100 dB. While you hear the mechanical relays if you get close to the unit, I could not detect any interruption or noise in the audio path. This is a superb implementation!
Microprocessor controlled protection circuit watches over the conditions of the device and shuts it down in extreme condition. What I like about it is that it auto recovers quickly and without user intervention. Firmware input support is provided for future refinement of this functional if needed.
Note that the extensive functionality makes the device a bit harder to use. You can easily get yourself in modes where you are not getting sound and wondering why. In this case, the level display is super helpful. As is the remote which automates some settings such as gain and RCA vs XLR input. You can also create two provides and recall them using C1 and C2 switches.
There is a ton of functionality here that would take me days to test. So I made a choice to make abbreviated preamp tests and then balanced headphone output.
Topping A70 Pro Preamplifier Measurements
Let's start with balanced input and output with variable volume control:
FFT display shows no recognizable distortion spikes other than the signal generator out of my audio analyzer! We are basically bound by signal to noise ratio which sets the overall SINAD to 121 dB (6 dB better than transparency under all conditions). Switching to RCA in/out surprisingly upped the performance a bit:
Balanced mode does provide more output though:
Finally here is our SNR:
Headphone performance should be highly indicative of preamp so let's get into that.
Topping A70 Pro Headphone Amplifier Measurements
As noted, I limited my tests to XLR balanced headphone output. Let's pump 4 volts into it and adjust volume to get 4 volts out:
We get the same great performance as we did in pre-amp mode. RCA input this time did cost us a bit as it normally does:
These are superb measurements, albeit just a hair off from best there is due to lack of an ultra low gain mode that some other Topping products have:
Noise performance shows why XLR input is a bit better:
50 mv output mode delivers near top of the class performance:
Frequency response is exceptionally flat:
Multitone performance is superb:
Power is just about everything in headphone amplifiers so let's see how we do there:
Wow, we have over 8 watts driving dual channels simultaneously at 32 ohm! Even low gain with its superbly low noise delivers 2 watts.
Changing the load from 600 ohm down to punishing 12 ohm shows superb ability to hold up the output voltage and hence keep delivering more and more power:
This is in entirely different class than any headphone amplifier I have tested!
I usually don't run the channel matching test with R2R relay volume controls but ran it here to show the superb implementation:
The dashed blue line shows deviation between the two channels. As you see, all the way down to the limit of -100 dB it remains at 0. Absolutely great!
Topping A70 Pro Headphone Listening Tests
I started testing my with everyday, low impedance and difficult to drive Dan Clark Stealth headphone. Even in low gain the A70 Pro drove these to almost ear bleeding levels and superb dynamics. Switching to high gains provided essentially infinite headroom and extra volume. Try as I might, I could not dare going past -15 dB. With other headphone amps, I could hear distortion at the maximum volume (or not enough volume). Both of those limits are long, long gone with the A70 Pro. You have so much power that any distortion or problems are clearly that of the headphone.
Switching for Sennheiser HD650 once again showed the incredible power reserves of the A70 Pro, allowing these headphones to shine with incredible detail and dynamics. There was no hint of any background noise and as noted, volume control was smooth, responsive and delight to adjust.
Conclusions
With A70 Pro, Topping pushes boundaries on multiple fronts. The device is gorgeous to look at, and informative and highly responsive to use. Power is increased to where it needs to be to drive even the most difficult to drive headphone as if it is a walk in the park. Measured performance is state of the art providing assurance of transparency. Subjective testing results couldn't be better. For a person who pushes amps to their max to see and hear the limits, I was out of a job with A70 Pro! There is not a negative here of any sort or shape. Yes, $499 is the price to pay. I suggest saving up money until you can afford to buy one if you are a serious headphone listener.
It is my pleasure to recommend the Topping A70 Pro. I am not sure how anything better can be designed but I am sure Topping will keep working at it!
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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