• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Topping A90 Headphone Amplifier Review

fieldcar

Addicted to Fun and Learning
Joined
Sep 27, 2019
Messages
821
Likes
1,258
Location
Milwaukee, Wisconsin, USA
Beautiful board!
I Iove mean well power supplies. I use them at work all the time for powering my analog devices.

irm-20-15
https://www.meanwellusa.com/productPdf.aspx?i=682

I wonder if the amplification circuit is rf shielded underneath the heatsink. It almost looks that way with the solder points being on the perimeter of the where the heatsink is positioned over the PCB.

Damn. I should have saved my cash for this spectacular amp. Oh well I guess I'll moap around with my 789.
 

Veri

Master Contributor
Joined
Feb 6, 2018
Messages
9,596
Likes
12,036
There must be some good feedback compensation in circuit design.
There for sure is :D:cool: amazing achievement by Topping. Especially since it has not been long since THX AAA was all the rage/ the best performer!
 

kn0ppers

Active Member
Joined
Jul 4, 2019
Messages
192
Likes
258
Location
Germany
I can't see any EMI/ESD/overvoltage protection at the inputs, are they hidden or is it just my eyes&brain?

I noticed that as well. Some BAV99 or similar wouldn't have been that expensive...or maybe we are both blind.

This is unbelievable! TPA6120 is very hard to implement correctly, all of existing products all have 10ohms output impedance. A90 has near zero impedance, and THDN is even better than TPA6120 data sheet. There must be some good feedback compensation in circuit design.

Hard to implement correctly? There is an extensive datasheet and evaluation board designs, giving you basically all you need to know. Getting it implemented "correctly" (whatever that means to you, for me it means stability with a solid phase margin) with 10 Ohms output impedance is not hard, you just follow the datasheet. After that, read up on VFA-CFA composite amplifiers and what to pay attention to. Yes lowering the output impedance isn't easy, that's the tricky bit. I have seen ferrite beads (suboptimal) in parallel to the 10 Ohm resistor as well as air cored inductors (there even is a thread in the DIY section here about it). The third and probably best option is a nested feedback approach incorporating feedback after the isolation resistor, which then indeed becomes potentially much more challenging. This is obviously what was done here, you can even see the thin feedback traces running next to the fat output traces because the feedback is taken from the point where the signal enters the output relay. At least I think thats what I am seeing.
But saying that it is impressive because the THD+N is better than the TPA6120A2 datasheet? You know thats kind of the whole point of pairing up a high-current, high-speed CFA like this with a precision control OpAmp, right..?

Apart from that? Mean Well IRM Power Supplies with filtering, 1A LDOs (TPS7A33/47), OPA1612s, no real surprises here if you know Topping and read some of JohnYangs contributions quite a while back.

What I am surprised to see is that the case has no ventilation. From my experience the Mean Well IRM modules can get quite toasty after a while. Sure they are SMPS, but their efficiency under light to medium loads (which they will be seing most of the time) isn't that great.

Overall very nice performance, but unlike others, I don't feel any need whatsoever to replace my current headamp with it.
 
Last edited:

bboris77

Senior Member
Joined
Oct 23, 2018
Messages
444
Likes
931
But if they made the best possible A70 it would be an A90... wouldn’t it?
Don’t get me wrong, I’m a happy D70 owner too - I’m just not sure what a slightly less-good A70 would be...
I just looked at the measurements and it seems that they would stack ok...the A90 is a bit smaller in every direction, so it would be a mini-pyramid :) If anyone has pictures of the two together, could you please post them?
 

DavidBloch406

Member
Joined
Apr 6, 2020
Messages
26
Likes
31
I noticed that as well. Some BAV99 or similar wouldn't have been that expensive...or maybe we are both blind.



Hard to implement correctly? There is an extensive datasheet and evaluation board designs, giving you basically all you need to know. Getting it implemented "correctly" (whatever that means to you, for me it means stability with a solid phase margin) with 10 Ohms output impedance is not hard, you just follow the datasheet. After that, read up on VFA-CFA composite amplifiers and what to pay attention to. Yes lowering the output impedance isn't easy, that's the tricky bit. I have seen ferrite beads (suboptimal) in parallel to the 10 Ohm resistor as well as air cored inductors (there even is a thread in the DIY section here about it). The third and probably best option is a nested feedback approach incorporating feedback after the isolation resistor, which then indeed becomes potentially much more challenging. This is obviously what was done here, you can even see the thin feedback traces running next to the fat output traces because the feedback is taken from the point where the signal enters the output relay. At least I think thats what I am seeing.
But saying that it is impressive because the THD+N is better than the TPA6120A2 datasheet? You know thats kind of the whole point of pairing up a high-current, high-speed CFA like this with a precision control OpAmp, right..?

Apart from that? Mean Well IRM Power Supplies, CLC Filtering, 1A LDOs (TPS7A33/47), OPA1612s, no real surprises here if you know Topping and read some of JohnYangs contributions quite a while back.

What I am surprised to see is that the case has no ventilation. From my experience the Mean Well IRM modules can get quite toasty after a while. Sure they are SMPS, but their efficiency under light to medium loads (which they will be seing most of the time) isn't that great.

Overall very nice performance, but unlike others, I don't feel any need whatsoever to replace my current headamp with it.
Thank you, this is really helpful. I appreciate the measurements but I’m interested in the engineering decisions being made here and you’ve made some compelling points. Hope others come onboard and open up the discussion some more
 

HDavidson

Active Member
Joined
Jun 1, 2019
Messages
151
Likes
113
But if they made the best possible A70 it would be an A90... wouldn’t it?
Don’t get me wrong, I’m a happy D70 owner too - I’m just not sure what a slightly less-good A70 would be...
Just for that :D
 

Attachments

  • tr-cas.jpg
    tr-cas.jpg
    66.4 KB · Views: 865

ichonderoga

Active Member
Forum Donor
Joined
Sep 21, 2019
Messages
152
Likes
160
I'm such a sucker for devices with awesome measurements. This and the Benchmark AHB2 would complete my D90 setup :) ... while also making me cashless! :-(
 

JohnYang1997

Master Contributor
Technical Expert
Audio Company
Joined
Dec 28, 2018
Messages
7,175
Likes
18,292
Location
China
I was a little disappointed when I saw the volume pot in the picture of the board. Topping, is this volume pot a joke?
That's a customized 4 gang pot of 5KOhm each wiring in parallel. The tracking is pretty outstanding if you can get your hands on one. There was another novel connection implemented but that reduces perceived gain and doesn't improve all that much considering there's low gain setting. You can run 120+db/mW IEM out of this.
 

bboris77

Senior Member
Joined
Oct 23, 2018
Messages
444
Likes
931
That's a customized pot of 5KOhm each wiring in parallel. The tracking is pretty outstanding if you can get your hands on one.
But it is not big enough....lol, just joking. Size is not everything. Plus, the shaft looks gold plated. Ok, enough Freudian symbolism. All joking aside, what is that 1/4 inch headphone jack? I have never seen a completely sealed jack with no exposed contacts. Not on amplifiers or guitars. Looks very sleek.
 

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
index.php


One also has to take price point and dimensions (alignment) on front panel into consideration.
Small sized pots, and certainly log type is pretty difficult to make. Especially when it is 4 gang (true balanced)

The one an owner finally gets could be similar, better or worse. Tolerances are a biatch.
 

JohnYang1997

Master Contributor
Technical Expert
Audio Company
Joined
Dec 28, 2018
Messages
7,175
Likes
18,292
Location
China
I noticed that as well. Some BAV99 or similar wouldn't have been that expensive...or maybe we are both blind.



Hard to implement correctly? There is an extensive datasheet and evaluation board designs, giving you basically all you need to know. Getting it implemented "correctly" (whatever that means to you, for me it means stability with a solid phase margin) with 10 Ohms output impedance is not hard, you just follow the datasheet. After that, read up on VFA-CFA composite amplifiers and what to pay attention to. Yes lowering the output impedance isn't easy, that's the tricky bit. I have seen ferrite beads (suboptimal) in parallel to the 10 Ohm resistor as well as air cored inductors (there even is a thread in the DIY section here about it). The third and probably best option is a nested feedback approach incorporating feedback after the isolation resistor, which then indeed becomes potentially much more challenging. This is obviously what was done here, you can even see the thin feedback traces running next to the fat output traces because the feedback is taken from the point where the signal enters the output relay. At least I think thats what I am seeing.
But saying that it is impressive because the THD+N is better than the TPA6120A2 datasheet? You know thats kind of the whole point of pairing up a high-current, high-speed CFA like this with a precision control OpAmp, right..?

Apart from that? Mean Well IRM Power Supplies, CLC Filtering, 1A LDOs (TPS7A33/47), OPA1612s, no real surprises here if you know Topping and read some of JohnYangs contributions quite a while back.

What I am surprised to see is that the case has no ventilation. From my experience the Mean Well IRM modules can get quite toasty after a while. Sure they are SMPS, but their efficiency under light to medium loads (which they will be seing most of the time) isn't that great.

Overall very nice performance, but unlike others, I don't feel any need whatsoever to replace my current headamp with it.
There's a large heatsink covering all 6120s with thermal compound applied. The realistic use case suggests that it will only run warm. And it's the same as THX amps(which runs on higher quiescent current and no external heatsink). The surface area of the chassis is good enough. In smaller sized L30, some sorts ventilation is implemented and reduced the temperature a few degrees just to make it more comfortable to touch.
 
Top Bottom