Topping LA90 evaluation and discussion (Integrated Amplifier)

[antcollinet]

Sure, but it says the same as Audiophonics' minor specs showed;

View attachment 203023

So I can understand why the matter was raised by @boXem | audio as to whether this amp could drive a 2 ohm load. I think along the way there was some confusion between driving a 2 ohm load and dips into the 2 - 3 ohm region, which is all now moot anyway as per further testing results. I think we can lay this non-issue to rest.


JSmith

I'm not convinced it is a non issue.

Amir has tested one device with a specific load, and with that load (with a specific frequency/impedance response) it can do better than the specifications state. How confident are we that all devices with all loads will work? Why would the manufacturer state a limit on impedance, if they were confident it can do better in all circumstances?

So if I were to buy one of these to run bridged with my 6 ohm (nominal) speakers, and the amp didn't work with them, what would Topping say if I requested a refund? They'd be well within their rights to point to this spec and say "get different speakers". What would they say if the amp went into oscillation and failed? (this is probably a high feedback amp) They might legitimately say "you misused it".

The fact that specification exists is a huge problem, regardless of Amir's tests.

 

[JSmith]

The fact that specification exists is a huge problem, regardless of Amir's tests.

Fair point, I agree, as one probably can't refer to the tests here if requesting a resolution to a possible problem on that basis. @JohnYang1997 will Topping be updating the spec's to reflect this tested capability or what is the official company position on this? I suppose there is onus on the buyer to do their homework too in relation to their specific requirements of usage, caveat emptor as always.

Regardless of these small specific use case items, the performance design behind this amp is superb and most surely is an achievement.


JSmith

 

[pjug]

I'm not convinced it is a non issue.

Amir has tested one device with a specific load, and with that load (with a specific frequency/impedance response) it can do better than the specifications state. How confident are we that all devices with all loads will work? Why would the manufacturer state a limit on impedance, if they were confident it can do better in all circumstances?

So if I were to buy one of these to run bridged with my 6 ohm (nominal) speakers, and the amp didn't work with them, what would Topping say if I requested a refund? They'd be well within their rights to point to this spec and say "get different speakers". What would they say if the amp went into oscillation and failed? (this is probably a high feedback amp) They might legitimately say "you misused it".

The fact that specification exists is a huge problem, regardless of Amir's tests.

IF this is using the LM3886 there is good reason for Topping to use the 8 ohm bridging spec. All the TI design info recommends keeping the device power dissipation under the 50W ballpark. The design spreadsheet doesn't even allow entering below 4 ohms for stereo. The application note gives this on bridging:

Therefore, using a bridged configuration, Vcc would have to be equal to ±20V to keep the IC's power
dissipation within 40W/IC when driving a 4Ω load! This equates to about 110W of output power in bridgedmode
driving a 4Ω load. When driving an 8Ω load, and using the same bridged pdmax equation and a
maximum of 40W/IC of power dissipation, the supply voltages would have to be ±28V. This equates to
about 120W of output power.

The TI docs are nicely collected here:

A Complete Guide to Design and Build a Hi-Fi LM3886 Amplifier

See how each part of the circuit works, how to calculate the best component values, and how to layout the PCB and wire your amplifier for great sound.

www.circuitbasics.com

 

[solderdude]

Fair point, I agree, as one probably can't refer to the tests here if requesting a resolution to a possible problem on that basis. @JohnYang1997 will Topping be updating the spec's to reflect this tested capability or what is the official company position on this? I suppose there is onus on the buyer to do their homework too in relation to their specific requirements of usage, caveat emptor as always.

Regardless of these small specific use case items, the performance design behind this amp is superb and most surely is an achievement.


JSmith

Amirs measurements are abundantly clear. The amp is current limited and the specs are correct.
4 ohm or more for stereo usage and 8 ohm or more for bridged operation.
It is what bridged operation is for. Specifically for higher impedance speakers so the output voltage is not the limiting factor.

Of course, due to current limiting and over temp detection (acc. to Amirm) you can even connect a 1 ohm load and you will get 25W into 1 ohm.
That doesn't mean you should use it with speakers dipping to 1 ohm.

Also speakers often only dip in specific frequency bands. As music consists of a wide spectral range (with the majority of signal below 500Hz) this also means that a speaker that is nominal 4 ohm may well drop to 2 ohm in a specific frequency range.
With music that means that for some frequencies the load may well be 20 ohm and 2 ohm dips at other frequencies the 2 ohm load will never actually reach full output voltage only. Only lower levels at the 2 ohm load so that won't ever current clip. The other frequencies may well be above 4 ohm and also will not be at full output voltage so will also not draw the max current.
For this reason even a peak reaching clipping voltage does not mean the current thus always reaches a maximum. Only during single tone measurements it will. This is NOT an actual use case.

So most likely 1 ohm is not something that will blow up this design (due to current limits) but will make the amp to become hotter much quicker.
Maybe... vertical and wider spaced heatsink fins could help keeping temperature down but I reckon looks are also important for buyers.

So there you have it. Test bench 2 ohm is not the same as speaker dips at 2 ohm when using music.

 

[JSmith]

a speaker that is nominal 4 ohm may well drop to 2 ohm in a specific frequency range.

Yes, my speakers dip to 2.6 ohms at around 200Hz.


JSmith

 

[solderdude]

This does not have to be an issue depending on how 'wide' that dip is and how much 'energy' is in that frequency band opposite 0dBFS output voltage.

 

[TheBatsEar]

I'm not convinced it is a non issue.

Amir has tested one device with a specific load, and with that load (with a specific frequency/impedance response) it can do better than the specifications state. How confident are we that all devices with all loads will work? Why would the manufacturer state a limit on impedance, if they were confident it can do better in all circumstances?

Even a giant like Yamaha says 4 to 8 ohms on any of their amps. Nobody tested it with any possible load either. All will continue playing if the load dips below 4 ohms.
The question "How confident are we that all devices with all loads will work?" can not be answered for any device on earth in the positive.

So if I were to buy one of these to run bridged with my 6 ohm (nominal) speakers, and the amp didn't work with them, what would Topping say if I requested a refund? They'd be well within their rights to point to this spec and say "get different speakers".

Why would it not work with your 6 ohm speaker?
What if my grandmother had wheels, would we have to call her "bike"?

The fact that specification exists is a huge problem, regardless of Amir's tests.

Bro, i ...

 

[antcollinet]

Even a giant like Yamaha says 4 to 8 ohms on any of their amps. Nobody tested it with any possible load either. All will continue playing if the load dips below 4 ohms.
The question "How confident are we that all devices with all loads will work?" can not be answered for any device on earth in the positive.


Why would it not work with your 6 ohm speaker?
What if my grandmother had wheels, would we have to call her "bike"?


Bro, i ...
View attachment 203082

Why? Because Topping says it is below the specified 8ohm. I have no idea how it might cause problems - presumably topping does, ask them : they wrote the requirement.


And I have no idea what that cat pic means

 

[TheBatsEar]

Why? Because Topping says it is below the specified 8ohm.

Either i didn't see it or you failed to mention that you want to use a 6 ohms speaker in the bridged configuration.

If you want to bridge, the spec says 8 ohms. Your 6 ohms speaker will not be the right one for the amp.
If you want to use the 6 ohms speaker regardless, you can not bridge.

What is the confusion?

And I have no idea what that cat pic means

Who does, friend, who does.

 

[raest]

Either i didn't see it or you failed to mention that you want to use a 6 ohms speaker in the bridged configuration.

indeed, in your overzealous (borderline irrational) defense of this product you failed to read his clear and unambiguous statement with which he began his second paragraph, a statement which you even quoted in the your response to his very legitimate concern

 

[TheBatsEar]

indeed, in your overzealous (borderline irrational) defense of this product

That's me sometimes, i apologize. All i wanted to say is this: stay within the manufacturers specs and everything is peachy.

Have a cat, it has calming properties:

 

[antcollinet]

Either i didn't see it or you failed to mention that you want to use a 6 ohms speaker in the bridged configuration.

If you want to bridge, the spec says 8 ohms. Your 6 ohms speaker will not be the right one for the amp.
If you want to use the 6 ohms speaker regardless, you can not bridge.

What is the confusion?


View attachment 203188
Who does, friend, who does.

I mentioned my 6ohm speakers.

I have no confusion.

Some are saying (or at least suggesting) that because Amir has tetsted bridged at 4ohm, that the spec can be ignored. I'm saying it can't.

Thanks for the cat

 

[TheBatsEar]

Some are saying (or at least suggesting) that because Amir has tetsted bridged at 4ohm, that the spec can be ignored. I'm saying it can't.

And i agree.

Thanks for the cat

Don't mention it.

 

[aravena562]

And i agree.


Don't mention it.
View attachment 203239

because it could not be used with 6 ohm speakers? if in the test at 4ohm in bridge mode it performed well?

 

[antcollinet]

because it could not be used with 6 ohm speakers? if in the test at 4ohm in bridge mode it performed well?

See my post here:

Topping LA90 evaluation and discussion (Integrated Amplifier)

Sure, but it says the same as Audiophonics' minor specs showed; So I can understand why the matter was raised by @boXem | audio as to whether this amp could drive a 2 ohm load. I think along the way there was some confusion between driving a 2 ohm load and dips into the 2 - 3 ohm region...

audiosciencereview.com

Topping say it must be used with 8ohm or greater in bridged mode. That is a problem regardless of Amir's test.

 

[TheBatsEar]

because it could not be used with 6 ohm speakers? if in the test at 4ohm in bridge mode it performed well?

• You can try to use this amp as a step to reach hard to reach places.
• You could use it as a dimmer for a lamp.
• You try to power your soldering iron with this amp.
• You could use it as a variable power supply for AC.
• You could use it with a 6 ohm speaker in bridged mode.

This would all work. But the manufacturer says to use it on speakers 4 ohms (stereo) or 8 ohms (bridged) or higher.
Amir merely showed the amp doesn't switch off or catch fire if the load drops below the recommended, because that was a concern.

Topping say it must be used with 8ohm or greater in bridged mode. That is a problem regardless of Amir's test.

Why is that a PROBLEM with Topping? Just use a 8 ohm rated speaker.

It's like saying this car trailer is rated for 750kg load, that is a problem for the manufacturer, because measurements show it will not collapse at 900kg.
If you need to haul 900kg, either drive twice, use the trailer against it's rating or buy another trailer. Its your problem, not the manufacturers.


A Yamaha R-S700, A-S700/701/801, minimum 4 ohms:

A Yamaha R-S202D, minimum 8 ohms:

Yamaha A-1020, minimum 4 ohm (it's complicated):

Yamaha A-S1000, minimum 4 ohm:

One has a minimum rating of 8 ohms. Is this a problem with Yamaha?
It is not. Just use 8 ohm speakers or buy another amp.

 

[DSJR]

I took it that bridged, this amp CAN drive a 4 ohm speaker using music in a typical domestic setting, but the potential for very hot running on test tones into 4 ohms made it inadvisable to 'recommend' it as such...

 

[antcollinet]

Why is that a PROBLEM with Topping? Just use a 8 ohm rated speaker.

The point I am making (and it seems I have to KEEP on making it).

Regardless of the test Amir has done at 4ohm, the specifications written by Topping are not rendered void by that testing.

Those specs make the amp usless for my use case - bridged with a 6 ohm speaker. I'll not buy one ignoring those specs just because Amir has tested one combination at 4ohm.

I fully accept that not everyone has the same use case, and some (though probably not many for bridged mode**) may want to use it with an 8ohm speaker.


**I have three pairs of main speakers in the house - they are all nominally 6 ohm.

 

[Vini darko]

Camp A. You need 1kw per channel 1Ω stable class D to even listen to music.
Camp B. Thinks camp A should ease back on the coffee.

 

[theREALdotnet]

Camp A. You need 1kw per channel 1Ω stable class D to even listen to music.
Camp B. Thinks camp A should ease back on the coffee.

Camp C: Camp A are wimps, or they only listen to sonatas for glass harmonica.