Topping LA90 Discrete Amplifier Review: speechless
This is a review and detailed measurements of the Topping LA90 Discrete balanced stereo amplifier. It was sent to me by the company and costs 899,-
The case is the same as the IC-based Topping LA90 which is fine with me given its high quality look and feel. The power switch doubles as input selector once the unit is on. Volume control can be bypassed using switch in the back:
As before, power is provided by a hefty, 64 volt switching power supply rated at 4 amps (likely provides higher current in short bursts). The amplifier as you see is all balanced with three inputs. You have a selection of low and high gains (although the latter should really be called medium gain). It can be bridged and nicely tolerates even 4 ohm loads in that mode. Trigger is provided to enable one power switch to turn on a series of devices.
Note that this is a traditional amplifier and not class D. There is no remote so if you need that, you have to use a DAC/pre-amp with that capability.
Topping LA90 Discrete Measurements
There is a lot to measure here given the fact that we have dual gains and bridge mode. Let’s work our way through it starting with low gain in stereo mode:
Incredibly, the LA90 Discrete matches the performance of its IC based unit, landing on its perch on top of all other amplifiers ever tested:
Switching to high gain costs you a few dBs but you are still ahead the competition:
So feel free to use this mode. Noise performance continues to be superb:
Frequency response is flat of course and load independent:
Crosstalk is better than average amplifier but is a step down from the regular LA90:
Multitone showcases the superbly low distortion levels:
Let’s see how we are doing in power department starting with 4 ohms:
We wind up good bit more power at 70 watts (vs 56 watts for normal LA90) while giving up nothing in spectacular noise and distortion department. Allowing for more distortion gets us more power:
8 Ohm performance follows the same path:
Tests so far have been at 1 kHz (other than multitone) so let’s vary that and see what happens:
In a word, wow! The amplifier simply doesn’t care what frequency you throw out it! This is a quite a step ahead of normal LA90 which itself was state of the art.
Power on is silent but off may create a faint noise depending on your speaker sensitivity:
Warm up showed one channel struggling a bit but later I found the power connector not fully tight so maybe that was the cause:
Regardless, it behaved correctly after a minute.
Topping LA90 Discrete Bridged Measurements
As with normal LA90, bridge mode still provides superb performance:
The name of the game is power though so let’s see what we get into 4 ohm:
Notice how we get more power but distortion is nowhere to be found until we clip.
Wow! This makes a great case for using a pair of these amps. You get so much power out of each one, rivalling much larger amplifiers.
Reactive Load Testing
The LA90 has a very sharp clipping point. This means that it goes from vanishingly low distortion to full clipping. Combine this with aggressive protection circuit which shuts the unit off and you have the make up of a system that can’t be measured in batch mode as my Powercube setup uses. If I set the voltage for 8 ohm load, then it causes the amp to shut down when driven at 4 ohm. Good news is that the amplifier doesn’t care about reactive loads. Here are the results for 8 ohm for example:
Maximum Output
4/11/2023
12:13 AM
Maximum Output Level Results
Selected Load Ch1 (Vrms) Ch2 (Vrms)
8 Ohm; 60 deg Capacitive 21.2 21.3
8 Ohm; 30 deg Capacitive 21.1 21.2
8 Ohm; 0 deg Resistive 21.0 21.0
8 Ohm; 30 deg Inductive 20.2 20.3
8 Ohm; 60 deg Inductive 20.9 21.0I could not get a similar output at 4 ohm due to limitation of the instrumentation as stated above. But if I drove the parameters manually, I could get it to tolerate reactive loads just as well.
Selecting 2 ohm caused the protection circuit to kick in. I didn’t have time to mess with that.
I spent nearly 2 hours trying to get this test done with the amplifier being pushed to clipping and shut down probably 50 to 100 times. Even though the case got pretty warm, the amp continued to function without complaining.
Conclusions
Traditionally in high-end audio when a company says they are using discrete designs, I get prepared for bad performance. Topping once again proves that this is no barrier for their designers. The discreate LA90 not only matches the exemplary performance of the IC based LA90, but betters it in power handling, producing more power (a needed feature). Pushing noise and distortion down in our top tier performance is very hard but Topping has no problem maintaining its significant lead over even best of the best amplifiers. Their skills and execution in this regard leaves me speechless.
Needless to say, it is my absolute pleasure to add Topping LA90 Discrete to my recommended list. Today is a happy day! 
