• 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 LA90 Review (Integrated Amplifier)

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 35 4.4%
  • 2. Not terrible (postman panther)

    Votes: 50 6.2%
  • 3. Fine (happy panther)

    Votes: 193 24.1%
  • 4. Great (golfing panther)

    Votes: 524 65.3%

  • Total voters
    802

mdsimon2

Major Contributor
Forum Donor
Joined
Oct 20, 2020
Messages
2,477
Likes
3,315
Location
Detroit, MI
I don't have enough technical knowledge in this field to authoritatively refute the claim. But I will take a stab at interpreting it, which is that the paper is looking for cost effective near field performance, rather than the best performance. There is little doubt that well-made active monitors offer the most cost effective hifi performance. The cost effective market has little overlap with the market for flagship products such as the la90.

In addition, the paper you quoted handpicked parameters such as the "typical listening volume" parameter without justification. I guess the author is lacking the tools that Amir has, or doesn't want to use them for some reason, but I would expect a 3d graph for each amplifier of thd+n vs frequency vs wattage if the author was trying to be thorough in making his point.

Finally, before the author's "cost compensation," significant differences do appear in the measurements.

TLDR: The paper does not "prove" to be that the loosely defined heuristic is a mathematical fact to my mathematically trained eyes.

You asked for the paper, I provided. I am not saying I agree with everything in it but I think it is clear that high distortion amplifiers can be used in really good sounding speakers (Genelec, Neumann, JBL, etc). This of course would imply that amplifier THD is just not that important to sound quality.

Here is a math question for you, what is the rough contribution on system THD of an amplifier with 0.05% THD when combined with a speaker with 0.5% THD? Do you think it is significant?

EDIT: To make my point even clearer, what amplifier do you think Amir uses when testing speakers on the Klippel? Do you think it is SINAD superstar? It is not -> https://www.audiosciencereview.com/...-about-speaker-measurements.11139/post-315631. And yet it is good enough to quantify performance of very high performance speakers.

I don't use their amplifier (it is too low power made for driver testing). The one I am using is one that I have reviewed before (Behringer A500): https://www.audiosciencereview.com/...easurements-of-behringer-a500-amplifier.5070/

Michael
 
Last edited:

kenshone

Active Member
Joined
May 15, 2022
Messages
197
Likes
103
You asked for the paper, I provided. I am not saying I agree with everything in it but I think it is clear that high distortion amplifiers can be used in really good sounding speakers (Genelec, Neumann, JBL, etc). This of course would imply that amplifier THD is just not that important to sound quality.

Here is a math question for you, what is the rough contribution on system THD of an amplifier with 0.05% THD when combined with a speaker with 0.5% THD? Do you think it is significant?

EDIT: To make my point even clearer, what amplifier do you think Amir uses when testing speakers on the Klippel? Do you think it is SINAD superstar? It's not -> https://www.audiosciencereview.com/...-about-speaker-measurements.11139/post-315631. And yet it is good enough to quantify performance of very high performance speakers.



Michael

I would say that's not a math question, but rather an EE question that happens to involve some (probably basic) math. I haven't studied EE.

Does Genelec admit that they actually use lower quality amps, or is this paper just trying to find some quasi-theoretical limit?
 

mdsimon2

Major Contributor
Forum Donor
Joined
Oct 20, 2020
Messages
2,477
Likes
3,315
Location
Detroit, MI
I would say that's not a math question, but rather an EE question that happens to involve some (probably basic) math. I haven't studied EE.

Does Genelec admit that they actually use lower quality amps, or is this paper just trying to find some quasi-theoretical limit?

Typical assumption is they add as sum of root squared. Combined THD = sqrt(0.005^2 + 0.0005^2) = 0.5025%, pretty darn close to 0.5% from the speaker.

I've not seen any measurements of the Genelec amplifiers but I have seen some teardowns that do not suggest super low distortion.


Michael
 

MCH

Major Contributor
Joined
Apr 10, 2021
Messages
2,581
Likes
2,197
You asked for the paper, I provided. I am not saying I agree with everything in it but I think it is clear that high distortion amplifiers can be used in really good sounding speakers (Genelec, Neumann, JBL, etc). This of course would imply that amplifier THD is just not that important to sound quality.

Here is a math question for you, what is the rough contribution on system THD of an amplifier with 0.05% THD when combined with a speaker with 0.5% THD? Do you think it is significant?

Michael
It is getting a bit off topic but i find this interesting, please help me to understand, because I have the feeling that the statement in that paper can be easily understood as "any half decent amplifier would do the job" but i think it is not trying to say that (again, this is more a question than a statement).

If i look at the distorsion graphs of the latest speaker reviews here, for instance the Polk ES20, at 349$ a pair, i see that above 2 kHz the THD is ca 0.1% at 86 db SPL (dont know how many watts you need to get there), that means that according to genelec standards you would need an amp that gives 0.01% THD above 2 kHz at said 86db. that is -80 db THD... If now i look at the graph of a much better speaker also reviewed recently, the kef reference 4C, at 86 db the THD seems to be well below 0,1% above 300 Hz (Difficult to see in the graph, maybe not far from 0.01-0.02?), what means you would need an amp generating -100 db THD at those frequencies and power to stay clear of the "one order of magnitude requirement"? not bad. Even at 96 db SPL the KEF seems to stay below 0.1% THD from 1 to 5 kHz.
Do i understand it correctly or am i missing something?
(if i said something very stupid please let me know asap so i can delete the message :p)
 

kenshone

Active Member
Joined
May 15, 2022
Messages
197
Likes
103
EDIT: To make my point even clearer, what amplifier do you think Amir uses when testing speakers on the Klippel? Do you think it is SINAD superstar? It is not -> https://www.audiosciencereview.com/...-about-speaker-measurements.11139/post-315631. And yet it is good enough to quantify performance of very high performance speakers.

Michael

That's fair enough. I'm more than happy to admit that I'm chasing performance that is ideally beyond audible, just like people who are much richer than me might buy a supercar with no intention of ever driving it at maximum speed.

But this is all quite different than the property I was trying to discover in this sub-thread, which is whether amps with inferior SINAD can be "overcome" through the characteristics of an active multi-amped speaker.

The Genelec paper was, per its abstract, only focused on active speakers. Do we have access to other papers which allow us to extrapolate the "results" of this paper to passive setups?
 

Billy Budapest

Major Contributor
Forum Donor
Joined
Oct 11, 2019
Messages
1,810
Likes
2,674
In case anyone is interested, Audiophonics has posted shots of the guts of the amp:

https://www.audiophonics.fr/46616-t...r-classe-ab-2x90w-4-ohm-1x180w-8-ohm-noir.jpg

https://www.audiophonics.fr/46617-t...r-classe-ab-2x90w-4-ohm-1x180w-8-ohm-noir.jpg
topping-la90-amplificateur-classe-ab-2x90w-4-ohm-1x180w-8-ohm-noir.jpg

topping-la90-amplificateur-classe-ab-2x90w-4-ohm-1x180w-8-ohm-noir.jpg
 

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
3,084
Likes
4,962
Location
Germany

TheBatsEar

Major Contributor
Forum Donor
Joined
Jun 16, 2020
Messages
3,084
Likes
4,962
Location
Germany
Large caps, lots of transistors, and some mystery sauce. :cool:
What are those solder blobs in the center of the main PCB?

Topping devices usually have a sticker somewhere, which shows, if broken, the customer was inside the box. That's why we didn't see any detailed pictures so far, i guess.
I'm tempted to buy one just to void the warranty.;)
 

Ra1zel

Addicted to Fun and Learning
Joined
Jul 6, 2021
Messages
531
Likes
1,048
Location
Poland
Do we have access to other papers which allow us to extrapolate the "results" of this paper to passive setups?
We can use the most basic math possible
120 SINAD DAC + 120 SINAD Amp = 117 SINAD chain, woah awesome.

Unfortunately we need transducer to listen to music, let's say state of the art speakers is 0.1% HD (60 SINAD) at 90dB and calculate the following chain SINAD again with speakers included.

Screenshot_20220524-130733_Chrome.jpg


Oh well... that's unfortunate. Even if your DAC was only -100dB thd and your amp -70dB you won't even degrade the sound quality more than 0.5dB beyond the "degradation" already introduced by our state of the art passive speaker.

That's why your whole electrical chain most likely doesn't matter beyond 0.01% HD. Speaker characteristics will always dominate the sound quality and that's the reason why actives usually are better since they can be optimized with internal EQ both in frequency domain and time domain and suffer no acoustic efficiency loss from passive xo.
 

Toku

Major Contributor
Joined
Apr 4, 2018
Messages
2,391
Likes
2,776
Location
Japan
Large caps, lots of transistors, and some mystery sauce. :cool:
What are those solder blobs in the center of the main PCB?
Is "solder blobs in the center of the main PCB" two circled parts? Even if you magnify the photo, you don't really understand what it is.
I'm also curious about the four soldering points on each of the L / R channels.
If it is a speaker output, it should be good in two places, but ...
 

Attachments

  • la90-pcb.jpg
    la90-pcb.jpg
    154.3 KB · Views: 2,607

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
Unfortunately we need transducer to listen to music, let's say state of the art speakers is 0.1% HD (60 SINAD) at 90dB and calculate the following chain SINAD again with speakers included.

Unfortunately it isn't as simple as that.
1: distortion levels change, in speakers even dramatically.
2: SINAD will be lower (noise dominated) at lower levels. As long as it stays below audible thresholds it is irrelevant.
3: Distortion profiles from speakers and electronics is vastly different.
4: SINAD numbers are only valid at 1kHz at a specified level (2V/4V/50mV/5W/certain wattage) into specific resistive loads and thus can be higher (or lower)

But yes, for sure, transducers are the worst offenders by far unless one plays some SET tube amps near full power.
Sometimes it is amazing how much of certain types of distortion can be present while still beautiful sounding.
 

Sokel

Master Contributor
Joined
Sep 8, 2021
Messages
5,840
Likes
5,775
Is "solder blobs in the center of the main PCB" two circled parts? Even if you magnify the photo, you don't really understand what it is.
Are there any screws at the bottom of the box underneath these blobs?

Edit:Shunt regulators that need cooling maybe?
 
Last edited:

pjug

Major Contributor
Forum Donor
Joined
Feb 2, 2019
Messages
1,775
Likes
1,561
So Topping covered the poweramp IC with a PCB to clamp it on the heatsink...

Looks like a rail splitter.


I suspect at least 2 of the LM317/377 are there to provide +/- 15V or something like that for the used opamps.

The other 2 could be part of a rail splitter or pre-regulation or 2 different +/- voltages ?


I think the current limiter may either be in the output IC or the power supply. Would need to redo the 4 ohm (bridged) test feeding just 1 channel.
That could give some clues.
Current limiter clips hard at 190W (28Vrms/4ohm (bridged) = 7.1Arms (peaks required = 9.9A) but this does not have to pass through a virtual ground.

Also what would be weird is that L and R channel would have their own rail splitter but expect the ground reference to be the same on both amps.
It would be silly to not use the same reference.

At 2 ohm (stereo) the current limits hard at 50W = 10Vrms (2 ohm) = 5Arms (peaks required = 7.1A) per channel.
Those currents would thus have to come through the rail splitter (also one channel used) or come from the reservoir caps.

Hoping @JohnYang1997 chimes in one day...
Anyone have more thoughts on how Topping is handling powering this with +64V, after seeing the internal photos? Has the idea that the output is capacitor coupled been ruled out? Is it possible that they use output capacitors and take feedback post capacitor. I was looking at the article linked below and wondering if this is essentially what they are doing.

edit: Oh I didn't read the above article very carefully. Cap is not in the feedback loop there. But it seems some people at least attempt this. Can anyone who has opened the amp tell us if the output is capacitively coupled? It would be nice to know if the idea can be ruled out.
 
Last edited:
Top Bottom