Topping LA90 Discrete Amplifier Review

[dsnyder0cnn]

How do find the performance of the LA90D so far?

Performance of the LA90D has been exemplary so far. I was initially using it in low-gain mode but had to switch to high-gain after adding FIR filters for digital room correction to overcome filter insertion loss. I'm still able to get levels up into the high 80's / low 90's dB range, which is plenty loud for this somewhat undertreated room.

In case you're curious about the corrections, here's the amplitude response relative to target (I've added a REL T/7i sub since taking the photo):

I still have three or four early reflections that I've not tamed, but step response shows strong correlation between channels after doing some phase correction to account for necessary asymmetric placement in this room.

I have a little bit of pre-ringing in the right channel but not enough to be audible. I used Acourate from AudioVero to build the FIR filters, which I apply using Roon's convolution engine. I created the REW plots you see above by saving sine sweeps with embedded timing reference to WAV files with REW. I then played the sweeps back in Roon while recording the output using REW. This gives me a great end-to-end test.

I'm using a mic that I've had calibrated by Cross Spectrum Labs.

The LA90D does a great job of getting out of the way and allowing the rest of the system to do its job.

 

[Swifty358]

For anyone having issues w/ the popping and crackling, I had the same issue and solved it by applying conductive grease to the amp banana connections. thought maybe my banana lost its "spring" but looking through this thread, its likely not entirely my cable's fault. Perhaps the LA90D is prone to less than perfect cable connections? Not sure, but I haven't had issues since applying the grease.

 

[Rhamnetin]

For anyone having issues w/ the popping and crackling, I had the same issue and solved it by applying conductive grease to the amp banana connections. thought maybe my banana lost its "spring" but looking through this thread, its likely not entirely my cable's fault. Perhaps the LA90D is prone to less than perfect cable connections? Not sure, but I haven't had issues since applying the grease.

Interesting. I wish they'd refresh it with Neutrik speakON connectors in any case.

 

[Swifty358]

Interesting. I wish they'd refresh it with Neutrik speakON connectors in any case.

Agreed

 

[jkorten]

This version is superior in every regard for the same money. I believe it will be replacing the IC based one soon if it has not already.

The specs may be great, I ordered one (with possibility of return fortunately) and the amp had no transparency at all (yes I broke it in for 24 hrs). Made my class D Hypex nc400s sound fantastic. Not a believer. Just sounds... meh.

 

[HarmonicTHD]

The specs may be great, I ordered one (with possibility of return fortunately) and the amp had no transparency at all (yes I broke it in for 24 hrs). Made my class D Hypex nc400s sound fantastic. Not a believer. Just sounds... meh.

Did you level match? This one has only 9dB gain in low gain mode.

 

[James Romeyn]

The specs may be great, I ordered one (with possibility of return fortunately) and the amp had no transparency at all (yes I broke it in for 24 hrs). Made my class D Hypex nc400s sound fantastic. Not a believer. Just sounds... meh.

Interesting. I had exactly the same reaction to the first LA90 IC version when I later compared it to a Schiit Audio Aegir (about 20W quasi-class A, cool running.) And I specifically refer to both amps not clipping but running within their respective power envelope driving a true 96 dB satellite. Aegir just had so much more beauty, density, expression and musical life.

By the time I had compared 1 Aegir to 1 LA90/IC I had already upgraded to 2 mono LA90/IC. So, I kept the single Aegir, sold the 2 LA90s and bought a 2nd Aegir for 2 mono blocks. Incidentally my speakers allow bi-amping; by huge margin 1 mono Aegir p/c outperformed 1 stereo Aegir p/c. Most recently a $20k SRP cool-running class A 100W stereo amp made 2 Aegir sound mediocre or worse.

 

[Triliza]

So what do you think could be the reason they sound so different? If it's not clipping, what is it, load dependency with your speaker? Less dynamic headroom? Something else?

 

[welwynnick]

There are lots of mix & match class D amp/SMPS options these days, and it's interesting to see the performance difference between shared and "dual mono" PSUs.
There are many good examples on ASR, but in general, more generous power supplies tend to give better performance.
I've done many power supply upgrades over the years (player/processor/amp) and it's not just about providing more current for low impedance speakers.

Power supply upgrade

It's time for an update, and I decided to order an R3 Power 00-3516 linear supply from Farnell, who delivered next day, from Belgium I think. Good service, and I also got the optional chassis cover. I got the last unit, sorry guys, but there are PLENTY of other options. This unit is muc...

www.meridianunplugged.com

PSU noise and ripple is usually specified at nominal output power, but almost invariably improves when the load is reduced.
So other things being equal, a bigger power supply is usually cleaner, as well as more powerful.
Great though the LA90D is in the most difficult conditions - bridged, high power, high load, high frequency - the wicked and greedy part of me can't help wondering what it would be like with a HYPEX SMPS1200A400 in a suitable box and cable?

Hypex SMPS1200A400 Switch Mode Power Supply

The SMPS1200A400 is a 1200W high efficiency switch mode power supply specially designed to be used in combination with our UcD and NCORE® amplifier modules

www.diyclassd.com

Nick

 

[Rhamnetin]

PSU noise and ripple is usually specified at nominal output power, but almost invariably improves when the load is reduced.
So other things being equal, a bigger power supply is usually cleaner, as well as more powerful.

Ultimately wouldn't these effects show up in THD+N vs power graphs? The LA90s are unrivaled there.

 

[welwynnick]

Yes, they're very good, aren't they?
Amplifier performance is often characterised by single numbers that don't give much insight, but is better done with two dimensional charts, which are typically:

1. Noise and distortion vs output frequency for single input frequency
2. Distortion vs input frequency for single output frequency
3. Distortion vs output power for single input frequency
4. Output power vs input frequency for single input frequency

I see each one of those as a two dimensional view of a four dimensional characteristic. They're better than single numbers, but you still don't see the whole picture, there's always something else going on that you're not looking at. Though I have to admit the LA90D does look cleaner than everything else, in every way, ever.

That PSU certainly does its job, but doesn't the best amplifier deserve something closer to "cost-no-object" instead of "cut every corner"? I think modern switching power supplies are a large part of the success of high performance amplifiers, with high efficiency, high frequency inversion and tight, wideband voltage regulation. That regulation supplies power on demand rather from storage, like conventional linear supplies, so the storage is relatively small. Bigger supplies have more storage, so demand can be met passively rather than actively, with better filtering for the load being drawn and less drop from nominal voltage.

I guess what I'm saying is that bigger power supplies are always better, and that 1200W Hypex supply really isn't a lot of money

 

[James Romeyn]

So what do you think could be the reason they sound so different? If it's not clipping, what is it, load dependency with your speaker? Less dynamic headroom? Something else?

I wish I knew! IMO based on my experience with 1 stereo and 2 mono Aegir and reading Jason's book (which I enjoyed,) Jason knows his "schiit" well. Speaker specs: 4/3-ohm nominal/minimum, benign load, 93 dB/M = 96 dB/2.83V. The designer is a renown pro-sound/home audio engineer. All or virtually all his prior models were designed with 8 to 16 ohm nominal impedance specifically for OTL amps; this particular model's impedance is too low for OTL. This is a sealed satellite with natural 2nd order bass roll off around 120 Hz to a distributed bass array with 2 sub amps in a modified version of Dr. David Griesinger's phase quadrature tuning. So, the main amp's contribution in this system continually decreases below 120 Hz down to about 20 Hz (about 2.5 octaves.)

The amp with $20k SRP employs a unique method to filter DC, has over 100 SMD bipolar outputs per channel and several (forgot the #) highly regulated power supplies throughout the circuit.

 

[Yoda896]

Anyone experienced electrostatic discharges using the LA90 Discrete?
I use it in the following setup Mac Mini -> D90SE -> A90 -> LA90 Discrete -> Speakers. The LA90 Discrete seems to have a grounding issue and gives me an ESD as soon as I touch it, the DAC or the preamp. Consequently the ESD causes a dropout of the DAC, the preamp and the LA90 Discrete. Without the LA90 using the A90 as a headphone amp there is no issue. Obviously the massiv power brick of LA90 Discrete is not grounded...
Any ideas for a fix?

 

[Billy Budapest]

Which retailer is selling the standard (discontinued) LA90 on closeout?

 

[jkorten]

So what do you think could be the reason they sound so different? If it's not clipping, what is it, load dependency with your speaker? Less dynamic headroom? Something else?

I believe they have a problem with the link between the power supply and the amp. The wire is too long and the quality of the wire is probably not good (a guess).

 

[abbazaba]

For anyone having issues w/ the popping and crackling, I had the same issue and solved it by applying conductive grease to the amp banana connections. thought maybe my banana lost its "spring" but looking through this thread, its likely not entirely my cable's fault. Perhaps the LA90D is prone to less than perfect cable connections? Not sure, but I haven't had issues since applying the grease.

This isn't an issue yet for me, but thank you so much for sharing. I also just noticed that Topping increased the warranty to 2 years for this model back in 2022 per the warranty page on their website.

Today is my last day for the Amazon return window, but I've had it since November with no issues and can't imagine going backward from this. I've had lots of DACs and amps over the years and the D70 Pro Sabre > LA90D combination is objectively amazing, and subjectively the best I've heard. I'd love to rationalize a second for that crazy bridged power.

 

[tmitchmd]

For anyone having issues w/ the popping and crackling, I had the same issue and solved it by applying conductive grease to the amp banana connections. thought maybe my banana lost its "spring" but looking through this thread, its likely not entirely my cable's fault. Perhaps the LA90D is prone to less than perfect cable connections? Not sure, but I haven't had issues since applying the grease.

Ingenious. What "conductive grease" product did you use?

 

[Swifty358]

Ingenious. What "conductive grease" product did you use?

https://www.amazon.com/NO-OX-ID-Special-Electrical-Contact-Corrosion/dp/B00HDF9EXE/ref=sr_1_5_pp?crid=TAUMYPLM7SGT&keywords=electrical+contact+grease&qid=1707249711&sprefix=electrical+contact+greas%2Caps%2C109&sr=8-5

I used this, NO-OX-ID "A-SPECIAL Electrical Grade"

 

[adLuke]

Hi all, I would like to have something cleared regarding gain and power.
I would like to know if there is a 'standard' gain that most amplifiers use.
Also I would like to know if the standard rule of 3db increase= double the power is valid when comparing different gains on the same amplifier or even different amplifiers: so an aplifier with 9db gain and 50w max power in 8ohms has the same spl of another amplifier with 12db gain and only 25w power into 8ohms?
Is the calculation a rough estimate or is it precise?
Thanks for any help on this.

 

[welwynnick]

For single ended inputs (RCA) amplifier gain is usually 28 to 29 dB.
For balanced inputs amplifier gain is usually around 23 dB.
3.01 dB (invariably referred to as 3dB) always represents a doubling of power, and 6dB is a doubling of voltage.
Max SPL is just a function of max power.
If an amp has higher gain, it needs less input voltage to achieve max power.