Topping A50s Headphone Amplifier Review

[Billy Budapest]

correction:

If you want to reach loud levels (say 110dB peak) the (original only) HE-6 requires 12.5V = 3.6W in 43 Ohm
The K1000 requires 9.5V = 0.6W in 150 Ohm.

No one should be listening through headphones at 110dB unless they want to go deaf!

 

[solderdude]

A little nuancing....

110dB peaks in music need to be reproduced to listen to 90-95dB average levels in very dynamic music. Which you can endure for a few minutes at most. Most recordings aren't really that dynamic but that doesn't mean high DR music is not essential to reproduce faithfully at impressive levels.

The usual '110dB' average level descriptions that most people refer to or mean is not the same and would mean a headphone would need to reach peaks up to 130dB to not distort. This indeed is not recommended and you really would not be able to listen to these levels anyway.

When one wants to listen to music and wants to reach really impressive levels (mostly bass notes) and maybe having turned up the bass a lot too and don't want to hear any distortion I keep a level of 120dB peak. Just to be sure.

Sane people listen at average levels between 70 and 85dB SPL (not phone) which requires much less power than people think (usually around 1 or a few mW)

 

[imagidominc]

Honestly... even though this performs better than my THX 789, I have no desire to buy this. The THX 789 is just THAT good, and I don't really feel the itch to "chase the dragon" that so many people find themselves in. I'm happy with what I got. And it wouldn't be that way if Amir didn't make his superb reviews. Thank you Amir!

 

[vkvedam]

Without a balanced input what's the point of balanced out?

Otherwise pretty good measurements but would L30 be a bargain unless someone's precisely looking for that form factor which matches D50/D50s.

 

[cubanmetalguy]

"Topping" the charts!!!

 

[JohnYang1997]

Without a balanced input what's the point of balanced out?

Otherwise pretty good measurements but would L30 be a bargain unless someone's precisely looking for that form factor which matches D50/D50s.

Hmmm. Balanced inputs has nothing to do with balanced output.
Balanced output has 4 separated amplifiers drive each end of each side of the headphones. You get much higher output voltage and power as well as much lower distortion because of no shared power ground and return current.

 

[vkvedam]

Hmmm. Balanced inputs has nothing to do with balanced output.
Balanced output has 4 separated amplifiers drive each end of each side of the headphones. You get much higher output voltage and power as well as much lower distortion because of no shared power ground and return current.

Thanks for the quick lesson, appreciate it! What's the point of balanced out then ?

 

[maxxevv]

No headphone NEEDS 1 watt—

The Raal SR1a was last heard shouting "Hold my beer ... "

 

[gvl]

You get much higher output voltage and power as well as much lower distortion because of no shared power ground and return current.

Why is the return current an issue? Resistance of the headphone cable? Just for my education.

 

[JohnYang1997]

Thanks for the quick lesson, appreciate it! What's the point of balanced out then ?

You mean balanced inputs?
The balanced interconnects are immune to external interference. Though it's inherently more noisy than single-end connection, the shield also serves as a leakage current return path. So there will be basically no supply noise even with SMPS. This also solves ground related issues pretty much 100%.
Another side effect (not necessarily Good or bad) is that it inherently has 6dB gain with same signal level flowing in each wire as unbalanced.

 

[JohnYang1997]

Why is the return current an issue? Resistance of the headphone cable? Just for my education.

Shared return current cause ground difference. No matter how you do it the little resistance in the jack limits the performance. With 16ohm you only get higher than -120dB distortion. With XLR jack even when the cold pins are ground the performance is still much better. -135dB or so for 16ohm load. So 15-20dB better performance.

 

[vkvedam]

You mean balanced inputs?
The balanced interconnects are immune to external interference. Though it's inherently more noisy than single-end connection, the shield also serves as a leakage current return path. So there will be basically no supply noise even with SMPS. This also solves ground related issues pretty much 100%.
Another side effect (not necessarily Good or bad) is that it inherently has 6dB gain with same signal level flowing in each wire as unbalanced.

Yeah, balanced out from a source into balanced inputs on an amp.

 

[Hemi-Demon]

I would have thought 2.5k is a little low for input impedance.

I can see the reason for the choice, however given that there are probably many sources with 10uF (or less) output coupling caps there is a risk that the -3dB point could occur well above 20Hz.

With a 10uF for example, the -3dB point occurs at ~ 6.5Hz which is ok (0.5dB at 20Hz) and unlikely to be audible.

But with a 1uF cap the -3dB point occurs at 66Hz which will most definitely be audible.

The THD will also rise markedly at very low frequencies with a small value cap.

What equipment would be a concern for potential rolloff, when used with the A50s, due to its input impedance? Just trying to learn. Thanks

 

[martin900]

Hopefully it's not like the 789 which measures good but sounds nowhere near as that...most of the 2nd hand ones have had like 5+ owners within a year, probably due to the "ASR-effect".

 

[Veri]

Hopefully it's not like the 789 which measures good but sounds nowhere near as that...

Erm, what? It sounds totally good. Nothing wrong with its sound whatsoever. Personally, my only complaint was the knob becoming scratchy very quickly... but besides that?

 

[Robbo99999]

An excellent product from Topping then, again! I'm a bit worried about the "[resonating] ear lobes" in this review (I guess for only a short time though), and I hope people are not emulating this too much...I think it's far better to listen at lower volumes and preserve your hearing, anything that permanently wrecks your body in some way is best left alone. I get the impression you get used to high volumes the more you listen to it, and on the same token I think you get used to listening at a lower volume and resisting the urge to turn it up.

 

[DLS79]

Not a bad thing in terms of performance I guess, but starting to feel a bit repetitive, given how often new models are released.

So buy one then, it's as simple as that!

I would imagine the idea is to give more inexpensive pared down alternatives to the A90.

That's my belive as well, not everyone wants or needs every option under the sun.

 

[audio_tony]

What equipment would be a concern for potential rolloff, when used with the A50s, due to its input impedance? Just trying to learn. Thanks

You would need to know if the equipment you want to use has capacitors in series with the output, and what the values of those capacitors are.

Most older equipment will have output capacitors.

Most computer sound cards have output capacitors.

That these devices have output capacitors is not an issue in itself - it's what the values of the capacitors are, should you want to use them with this headphone amp. Such things can only be discovered by looking at the circuit diagram for the device(s) or looking inside and tracing the signal path back from the output sockets.

 

[Ron Texas]

@amirm does the 6db gain setting apply to the line out?

 

[Veri]

@amirm does the 6db gain setting apply to the line out?

The pre-amp output is just the head-amp wired to an additional resistor as far as I know.