Topping A90 Discrete Review (Headphone Amp & Preamp)

[mrjayviper]

...and they are quiet!

ventilation holes are completely quiet and requires no maintenance or is not going to break down.

 

[trl]

So my amp is out of warranty and i want to drill some holes on top for ventilation.

How can i separate the board from the chassis?

I was watching a video where the person mention something about ribbon cables but he didn't show the disassembly.

Thanks

I've partially answered you here: https://www.audiosciencereview.com/...own-and-personal-thoughts.48717/#post-1747778.

However, a very detailed teardown guide I can't provide, but feel free to unscrew the backside screws that keep the backplate kept in place (you can also loose a bit the screws from the In/Out plugs too), then gently take the backplate out for about one inch until you'll see the two ribbon cables. With a small plier or a small screwdriver unsecure the connectors that keep the ribbons in place and plug them off. Worst part is getting a very long and really thin screwdriver able to reach to the two screws fron the front plate and also to fit between the power supplies and the side of the case (to reach the front screws).

If you haven't done teardowns before or if you don't have the right tools then you may find a local shop able to help you, perhaps a GSM repair shop would do it for you.

Stil, I can't figure out why do you want to drill those halls in the case for, given that the temp is not passing over 40 C?

 

[Sokel]

So my amp is out of warranty and i want to drill some holes on top for ventilation.

How can i separate the board from the chassis?

I was watching a video where the person mention something about ribbon cables but he didn't show the disassembly.

Thanks

You also have to find a way for the dust,etc not creep in.
Too much of a hustle to address everything right and the result might not be what you want,if it's not designed from the ground up us such any mod is questionable.

Edit:to define it a little,sometimes an even temp along the board is better than having an area cooled more than another,it's that difference that can break things too.

 

[Furyo]

This is a review and detailed measurements of the new Topping A90 Discrete balanced preamplifier and headphone amplifier. It was sent to me by the company and costs US $599.

View attachment 213870
Announcement was supposed to be a few hours from now but one of the distributor already released it so here we go. As you can tell, there is a new design in the form of those pin-hole LEDs which I find quite elegant. Inside there is stepped relay for volume control. Of course as the name indicates, this design uses discrete transistors rather than op-amps. 39 transistors are used to accomplish that task in each module. Will performance be as good as op-amps? And is there an advantage? We will find out in the measurement section. Here is the back panel:

View attachment 213871

I was pleasantly surprised to see the same extension connector to connect to Topping EXT90 to provide more inputs. In addition there is 12 volt trigger which many have been asking for. And even a ground lift switch.

In use, I found minor ticks during quiet parts of the music when changing the volume quickly. This is quite common in stepped relay implementations.

Topping A90 Discrete Measurements
In order to save time, all measurements are with balanced XLR input and balanced 4 pin XLR headphone output. Unbalanced has quarter of the power. Here is our dashboard:

View attachment 213872

While SINAD of 119 dB is superb and assures transparency in all conditions, it is a hair worse than A90:
View attachment 213873

This is incredible performance as every other discrete headphone amplifier I have tested has given a lot of performance (in the form of noise and distortion) to get there. Dynamic range is a bit lower which is responsible for that:
View attachment 213874

We see that penalty in the 50 mv test:
View attachment 213875

Multitone test shows how low the distortion products are:
View attachment 213876

Frequency response is of course extended and flat:

View attachment 213877

THD vs frequency shows a slight rise at the top end:
View attachment 213878

I measured power at three impedances: 300, 50 and 32:

View attachment 213879

View attachment 213880


View attachment 213881

The advantage of discrete implementation seems to be in current delivery into low impedances:
View attachment 213882

Usually I see a pull back at 32 ohm but here, that load doesn't impact the amp at all. It is not until we get to 20 ohm that the output voltage starts to drop a bit. This is a first since I started to make this measurement.

When pushed into protection with loads < 32 ohm, the unit shut off. Powering on everything was fine so it passed this stress test.

The beauty of stepped relay volume control is perfect channel matching which we see here:
View attachment 213883

I am amazed how well this works. Some stepped relay implementations lose their grip at low volumes but there we go past our limits of hearing before the mismatch even registers!

Topping A90 Discrete Listening Tests
I have been using my everyday Dan Clark Stealth headphone as a "it won't drive it but let's see what it does" test for headphone amps. This is the first time I have seen an amplifier have such an upper hand over these headphones. The sound is incredibly dynamic and beautiful. "Loud" listening is at volume level 80 in high gain. I cranked it up to 95 before I got scared for my hearing without any hint of distortion. I had not heard these headphones come to life so well.

Needless to say, driving Sennheiser HD650 and Drop Ether CX was in a walk in the park. I am talking incredible bass, detail and fidelity with volume indicator in 60s.

What a joy....

Conclusions
I must confess that I got a bit worried when Topping told me about the A90 Discrete. I worried that they were making a discrete version just to appease audiophiles but with much loss in noise and distortion metrics. Happily Topping approaches everything with extreme focus on performance and they managed to get the A90 discrete within a split hair of the op-amp version. But then innovated with stepped ladder volume control, trigger support and major step up in class/look of the unit. I happily take these as a trade off for that 1 dB of SINAD.

From design point of view, this is another watershed audio/engineering event brought to us by Topping. Who would have thought that this company would keep breaking new ground instead of all the major/usual names we know in hi-fi.

It is my pleasure to add Topping A90 Discrete headphone amplifier/pre-amplifier to my recommended list. My challenge is to figure out if it goes in my main system or desktop!

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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/

great test, as usual…one question, if I can: two power suppliers mean dual mono (one for the L channel and other for the R one) or not?

Thanks indeed to your time!

 

[trl]

@Furyo here's a teardown with the A90D: Topping A90 Discrete (A90D) - Teardown and personal thoughts. I suppose we can call it dual mono, but I usually call dual mono when there are separate PCBs, although I don't really think it matters if dual mono or not if the channel separation is higher than 80 dB.

 

[Furyo]

I am agree with you, but I like so much if my devices has got two separated lines of supply…by the way you are not sure if is in this way,
About dual mono, not necessary is with two separated pcbs, but only if there are a separated power supply for each channel

 

[mocenigo]

You also have to find a way for the dust,etc not creep in.
Too much of a hustle to address everything right and the result might not be what you want,if it's not designed from the ground up us such any mod is questionable.

Edit:to define it a little,sometimes an even temp along the board is better than having an area cooled more than another,it's that difference that can break things too.

I agree. In my build (so not a mod) I solved the dust problem by having holes in the bottom and in the rear of the amp, so the air enters from below and exits from the back. Also, not having the holes on the top helps with even temperature. I did not calculate or model the temperatures though, this was done out of common sense.

 

[kleijnforstm]

Hi, I have topping a90 discrete, what should I buy?
Motu m4 and connect trs (motu) to xlr (a90) or topping d90 and connect xlr(d90) to xlr(a90)?
Will there be a difference in sound? What will be better for audeze lcd-x?
Are there any other considerations I'm missing, or recommendations?

 

[trl]

MOTU M4 teardown here: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/ and measurements here: https://www.audiosciencereview.com/forum/index.php?threads/motu-m4-audio-interface-review.15757/.

Topping D90 teardown here: https://www.audiosciencereview.com/forum/index.php?threads/topping-d90-mqa-teardown.20457/ and measurements here: https://www.audiosciencereview.com/...ds/topping-d90-balanced-usb-dac-review.10519/

Also, A90D teardown here: https://www.audiosciencereview.com/...te-a90d-teardown-and-personal-thoughts.48717/ and measurements here: https://www.audiosciencereview.com/...0-discrete-review-headphone-amp-preamp.35114/, in case you might be interested in the discrete version of the A90.

If you need a decent ADC that is able to perform well on the playback part, at about 110dB SINAD, then M4 will do fine. I'm still using mine and I'm happy, although I alternate using D90 and M4, depending on the setup I choose at that moment.

LCD-X measurement here: https://www.audiosciencereview.com/forum/index.php?threads/audeze-lcd-x-over-ear-open-back-headphone-review.16777/ and here https://www.audiosciencereview.com/...ze-lcd-x-review-2021-edition-headphone.25271/.

If you only need a DAC, then I'd recommend D90 instead of M4, given that you don't need an ADC. However, the THD+N of your LCD-X is higher than the THD+N of any of the two combos from above, so you'll not hear any differences between the two setups.

 

[kleijnforstm]

MOTU M4 teardown here: https://www.audiosciencereview.com/...analysis-and-few-in-house-measurements.17819/ and measurements here: https://www.audiosciencereview.com/forum/index.php?threads/motu-m4-audio-interface-review.15757/.

Topping D90 teardown here: https://www.audiosciencereview.com/forum/index.php?threads/topping-d90-mqa-teardown.20457/ and measurements here:

Also, A90D teardown here: https://www.audiosciencereview.com/...te-a90d-teardown-and-personal-thoughts.48717/ and measurements here: https://www.audiosciencereview.com/...0-discrete-review-headphone-amp-preamp.35114/, in case you might be interested in the discrete version of the A90.

If you need a decent ADC that is able to perform well on the playback part, at about 110dB SINAD, then M4 will do fine. I'm still using mine and I'm happy, although I alternate using D90 and M4, depending on the setup I choose at that moment.

LCD-X measurement here: https://www.audiosciencereview.com/forum/index.php?threads/audeze-lcd-x-over-ear-open-back-headphone-review.16777/ and here https://www.audiosciencereview.com/...ze-lcd-x-review-2021-edition-headphone.25271/.

If you only need a DAC, then I'd recommend D90 instead of M4, given that you don't need an ADC. However, the THD+N of your LCD-X is higher than the THD+N of any of the two combos from above, so you'll not hear any differences between the two setups.

wow thanks, I'll choose D90

 

[PacketofCrisps]

Can someone tell on this amp on the line out can you choose between fixed and variable?

 

[staticV3]

Can someone tell on this amp on the line out can you choose between fixed and variable?

The A90D's volume knob cannot be disabled.

 

[zhgutov]

Actually you can kinda disable the volume knob, setting it to 99.
You can see the effect on the measurements.
It affects the crosstalk (H is high gain, horizontal line is the limit of my ADC):

I'm not sure if it is possible to hear (can't confirm that via AB test).
In any other way the preamp (volume knob) of A90D will probably do better job than anything else.

 

[John B]

Been using this amp semi regularly since July and the left channel started to get snow about a month back. It finally got too bad to listen to the thing. Anybody want a play by play on Topping's service responsiveness. I sent them an email just now but have never had to use them through the many products I purchased. Let me know!

 

[Music1969]

Topping A70 Pro is better than this right ?

Both enough power, both low noise and distortion

Both perfect channel balance

A70 Pro has higher input impedance and higher 50mv SNR - and is cheaper !

 

[formdissolve]

Topping A70 Pro is better than this right ?

Both enough power, both low noise and distortion

Both perfect channel balance

A70 Pro has higher input impedance and higher 50mv SNR - and is cheaper !

I actually had the same thoughts... I listen to headphones 95% of the time these days and with the EXT90 support on the A70 Pro, that kind of seals the deal. Apos has the A90D for $449 "certified used", but the A70 Pro is $499 new. The fact that the preamp measurements are as good as they are means I can use it with my 2ch system as well and swap out my SP400 to my office for this.

Those "T'ang-ku-la" modules inside look potted though, so hopefully they don't overheat?

 

[Music1969]

Those "T'ang-ku-la" modules inside look potted though, so hopefully they don't overheat?

A90D NFCA modules in A90D are potted too? Or not ? @trl mentioned here: Yesterday at 9:51 PM

The Tang Kula are advertised to be more efficient, lower temp for longer reliability (Topping say)

 

[raif71]

I actually had the same thoughts... I listen to headphones 95% of the time these days and with the EXT90 support on the A70 Pro, that kind of seals the deal. Apos has the A90D for $449 "certified used", but the A70 Pro is $499 new. The fact that the preamp measurements are as good as they are means I can use it with my 2ch system as well and swap out my SP400 to my office for this.

Those "T'ang-ku-la" modules inside look potted though, so hopefully they don't overheat?

I have the sp400. I look forward to your comparison of the sp400 and the A70 Pro

 

[trl]

A90D NFCA modules in A90D are potted too? Or not ? @trl mentioned here: Yesterday at 9:51 PM
[...]

Unfortunately yes, I thought you've seen the teardown already. I would have liked to see all the guts inside the NFCA modules from the A90D, but it's all sealed in melted resin and plastic.

 

[Music1969]

I have the sp400. I look forward to your comparison of the sp400 and the A70 Pro

SP400 is amazing

I had it also

But somehow something more amazing came in the A70 Pro