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Topping A90 Headphone Amplifier Review

Jimbob54

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Same function. I find 4.4mm the ideal ratio of size to robustness. Now 4pin xlr is the no frills mil-spec connection.

Ive had 4.4mm terminations on all my headphones that I choose to make balanced. I have xlr male to 4.4mm female extensions out of my amps (to get me to the sofa across the room). My only comment is a 4.4 to 4.4 link is far less robust than XLR to XLR on joints that may move. If I had my time again, I would terminate everything XLR and just buy a short XLR to 4.4 for the last inch or 2 when needed for conversion.
 

MalinYamato

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A THX AAA killer and it has a PENTACON out :) but $560 for me in Europa :(
 

MalinYamato

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Only advantage is being more compact.
,,,and may be universal for all amps and amp/dacs in the future, for portables as well as stationary amps. RIP 2.5, 3.5 and 6.3.
 

thefsb

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A function doesn't have more than one codomain (dependent) value for a given value of the domain (independent) variable. So I think I should understand each curve in this graph as plotting two different functions of the same independent variable. The value of one function (measured output power) is horizontal and the value of the other (measured THD+N) is vertical while the independent variable (input voltage?) is not shown. Diuc?
 

3125b

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For desktop use 4.4mm AUX would seem plenty robust to me, however XLR might have an advantage in longevity, or does it not?
Thats not to say that I´ve ever had any particular issues with AUX wearing out - or any other sort of data connector like USB for that matter.
 
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amirm

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A function doesn't have more than one codomain (dependent) value for a given value of the domain (independent) variable. So I think I should understand each curve in this graph as plotting two different functions of the same independent variable. The value of one function (measured output power) is horizontal and the value of the other (measured THD+N) is vertical while the independent variable (input voltage?) is not shown. Diuc?
Multiple measurements can be made from a single output. Here, the input to the amp is varied and the output waveform captured. One measurement extracted from this is the power. The other is distortion+noise (THD+N).

The input value is not shown because it is of less interest here. The sweep is from 10 millivolts to 4 volts from what I recall.
 

MWeston

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@JohnYang1997 Congrats on this stellar design! When I was on the Apos website, I was blown away by one of the pictures listing specs. It was showing maximum output voltage swing of 49Vpp in balanced mode. This seemed ground breaking for an integrated solution. Now that I see the PCB showing the power supplies, I don't get it. The TPA6120A can only swing +/-12.5Vp (assuming symmetry which it slightly isn't) on +/-15V rails. Each chip looks to have its outputs in parallel through 3.3 ohm resistors (not sure how that drops down to 0.1 ohm on the output but must be due to the feedback loop). Each chip is a phase of the output (L+,L-,R+,R-) so that is 25Vpp on the balanced output at max gain.

I'm not sure where the 49Vpp comes from. Are you suggesting I buy two and parallel the outputs? ;) Sounds like a fun challenge but not what was meant here. :) I'm just curious what I'm not seeing to come up with that number.

Thanks!


Michael
 

MalinYamato

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Multiple measurements can be made from a single output. Here, the input to the amp is varied and the output waveform captured. One measurement extracted from this is the power. The other is distortion+noise (THD+N).

The input value is not shown because it is of less interest here. The sweep is from 10 millivolts to 4 volts from what I recall.
whats the difference between noise and distortion, may distortion be said to cause noise?
 

ReaderZ

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Multiple measurements can be made from a single output. Here, the input to the amp is varied and the output waveform captured. One measurement extracted from this is the power. The other is distortion+noise (THD+N).

The input value is not shown because it is of less interest here. The sweep is from 10 millivolts to 4 volts from what I recall.


Any chance do some tests with RCA input as well?
 

JustAnandaDourEyedDude

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Is +/-12.5Vp the same as 25Vpp?

@JohnYang1997 Congrats on this stellar design! When I was on the Apos website, I was blown away by one of the pictures listing specs. It was showing maximum output voltage swing of 49Vpp in balanced mode. This seemed ground breaking for an integrated solution. Now that I see the PCB showing the power supplies, I don't get it. The TPA6120A can only swing +/-12.5Vp (assuming symmetry which it slightly isn't) on +/-15V rails. Each chip looks to have its outputs in parallel through 3.3 ohm resistors (not sure how that drops down to 0.1 ohm on the output but must be due to the feedback loop). Each chip is a phase of the output (L+,L-,R+,R-) so that is 25Vpp on the balanced output at max gain.

I'm not sure where the 49Vpp comes from. Are you suggesting I buy two and parallel the outputs? ;) Sounds like a fun challenge but not what was meant here. :) I'm just curious what I'm not seeing to come up with that number.

Thanks!


Michael
 
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amirm

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whats the difference between noise and distortion, may distortion be said to cause noise?
They are different things. Noise is random in general. Distortion is not (either correlated or not correlated to what is being amplified).

They are bundled together in this test because of historical reasons. A 1 kHz tone is fed to the device. What comes out is filtered with a sharp 1 kHz notch and all that is left is presented. By definition what is left is the sum of everything: distortion, noise, hum, etc.
 
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