Topping A50 III Headphone Amp Review

[KrispyJuniors]

Can anyone provide any insight on the actual topology of this amplifier?

I was under the impression that it is a bridged/floating output due to the measurements, product description and marketing language. The slightly lower SNR and slightly higher distortion pointed me to a summing/conversion stage. A bridged topology would make sense for the size and price of the amp. I was pretty confident in this conclusion, but I recently noticed a couple of Topping's fully differential amplifiers, such as the A90D and L70, exhibit similar measurement characteristics as the A50 III. This has really piqued my curiosity.

Does anyone know if the A50 III maintains a differential signal path from the input to the output, or if the balanced input is converted to single ended before the output stage. Can anyone find any concrete answers or a teardown to confirm?

 

[Roland68]

Can anyone provide any insight on the actual topology of this amplifier?

I was under the impression that it is a bridged/floating output due to the measurements, product description and marketing language. The slightly lower SNR and slightly higher distortion pointed me to a summing/conversion stage. A bridged topology would make sense for the size and price of the amp. I was pretty confident in this conclusion, but I recently noticed a couple of Topping's fully differential amplifiers, such as the A90D and L70, exhibit similar measurement characteristics as the A50 III. This has really piqued my curiosity.

Does anyone know if the A50 III maintains a differential signal path from the input to the output, or if the balanced input is converted to single ended before the output stage. Can anyone find any concrete answers or a teardown to confirm?

As far as I know, in the A50 III, the balanced input signal is immediately converted to unbalanced and only becomes balanced again right before the output stages. The same applies to the L70, A70 Pro, A90D, and so on.
Balanced signal transmission only makes sense externally—outside the devices. Internally, it offers no advantages and creates more problems than it solves.
Some people believe that balanced internal signal paths are something great or special, but ideally, balanced signals are converted to unbalanced at the input and only converted back to balanced at the output.

There are a few rare exceptions—headphone amplifiers with fully balanced signal paths—but their measurements show that there is no advantage to this approach.

 

[KrispyJuniors]

As far as I know, in the A50 III, the balanced input signal is immediately converted to unbalanced and only becomes balanced again right before the output stages. The same applies to the L70, A70 Pro, A90D, and so on.
Balanced signal transmission only makes sense externally—outside the devices. Internally, it offers no advantages and creates more problems than it solves.
Some people believe that balanced internal signal paths are something great or special, but ideally, balanced signals are converted to unbalanced at the input and only converted back to balanced at the output.

There are a few rare exceptions—headphone amplifiers with fully balanced signal paths—but their measurements show that there is no advantage to this approach.

Thanks for the sanity check! This is what I was thinking too, but I have been having trouble wrapping my head around the architecture. I figured for the size, price and complexity, it pretty much had to convert to single ended at the inputs. You're right, the measurements are so good, fully balanced wouldn't be worth the complexity.

 

[Roland68]

I get the feeling you’ve read some incorrect information somewhere about balanced devices or signal paths.
Balanced external signal transmission—such as via XLR cables—and internal balanced circuitry are two completely different things; they have nothing to do with each other.
While balanced cabling offers distinct advantages—such as the ability to eliminate interference, even over long cable runs—the situation is exactly the opposite for internal circuitry. Factors like component tolerances, volume control discrepancies (e.g., quad potentiometers), uneven interference pickup, and mismatched resistances within a balanced signal path actually degrade signal quality rather than providing any benefit.
The only practical application is in power amplifiers, where balanced amplifier stages allow for a fourfold increase in power output for a given power supply voltage. However, the noise components also add up, which is why the effort in development and tolerances in production are much more complex in order to obtain good measurement values.
In terms of sound quality, balanced amplifiers offer absolutely no advantage either.

This is clearly demonstrated by single-ended amplifiers like the Topping L30 II, L30, and L50, which consistently top the measurement charts, outperforming almost all balanced amplifiers.
The fact that the A50 III matches these models in measurements is a testament to the quality of its engineering.