Topping A90 Headphone Amplifier: Review

I’ve covered the Topping D90SE rather extensively and it remains one of my favorite affordable DACs in the category; it is very well engineered and sounds excellent. The Topping A90 has managed to slip through my fingers until now. It uses the same chassis as the D90 and works well with it — but it deserves to be considered outside of the Topping ecosystem.

The Chinese manufacturer produces a wide range of headphone amplifiers and DACs ranging in price from $100 up to $1,300 USD for the D90/A90 combination. Topping has been the recipient of almost giddy praise from the folks over at Audio Science Review because the products test exceptionally well, and the D90/A90 pairing delivers so many features and excellent performance for the money.

Topping didn’t design the circuit used in the A90 which is a nested feedback composite amplifier design, but they have gone a long way to perfect it. 

Design & Build 

The A90 uses an all-aluminum chassis available either in a brushed raw finish or anodized flat black. It stands just under two inches tall, and nine inches wide and is roughly 6 inches deep. The same chassis shared by the D90 and U90 models as well so it stacks neatly for use on small desktops.

If you are not familiar with the U90, it is the USB interface model and an excellent USB to Coaxial or Optical Converter. 

The front face has a series of 3 switches on the left side, headphone ports (XLR, 4.4mm balanced and 6.35mm single-ended) placed in the center and the volume knob is situated on the far right.

The first switch acts as the power switch and puts the A90 in either pre-amp mode or headphone amplifier mode depending on position. The second switch selects either XLR or RCA inputs, while the third controls the gain level of the amplifier. 

All of the controls and switches are accessible via the front panel which is always a plus. There is not a remote control provided which would be a nice addition for later models especially if used as a pre-amplifier.

The rear face has two pairs of XLR jacks and 2 pairs of RCAs; one each for input and outputs. The A90 can be used with two different sources via the selector switch on the front panel.

Internals

The Topping A90 is nested feedback design; this means that the A90 uses cascaded op-amps in conjunction with negative feedback loops that help control each op-amp. The way this works is an op-amp is placed at the output of the previous op-amp in the series and a negative feedback loop adjusts the output of each op-amp into the next. The outcome is an amp with a higher gain, faster slew rate, and lower distortion than an amp using the same op-amps in parallel.  

There are some hurdles that must be accounted for when working with a composite design; chief among them being a much higher output resistance than other designs.

Topping has handled this problem well as the output impedance is quite low. Another issue is that gain is usually lower in negative-feedback designs but here again, with nearly 8 watts of output power (balanced in, balanced out) the A90 is at no loss for power either.

Topping went so far as to challenge THX and their marketing campaign and the A90 does indeed measure at least as well as most THX implementations and beat many of them in tests by Topping, ASR, Soundguys, and others.

As a preamplifier it can output up to 18V on the low gain and up to 49V on the mid and high gain settings so it is capable of not only driving just about any headphone imaginable, but also works well with about any powered monitor one can think of and has more than enough power for most (even on low gain).  

A look at the specification sheet of the A90 tells you that Topping wasn’t shooting to make a good budget amp. They were shooting to make a fantastic amplifier regardless of price and the numbers suggest they succeeded. But numbers are not everything and unless it sounds good — all of the fancy test measurements mean nothing.

Sound 

The first thing I noticed about the A90 was how effortlessly it handled almost every headphone that I threw at it; that isn’t a claim that you can make about most affordable desktop headphone amplifiers.

From IEMs to the HE6, it never sounded stressed, and instead just took what you gave it in stride and with the gain switch in the proper position, it went from being quiet enough to use with the Andromeda to powerful enough to damage your hearing with a HiFiMAN HE6.

One test that highlights noise is to pause your music, and turn the volume knob all the way up and listen for hum or hiss. The Andromeda is known for having some hiss with most desktop amplifier setups, so I set the A90 on low gain and started listening with the volume at about the nine o’clock position on the dial — which produced zero hiss or noise.

I kept going on the volume dial until I was in danger of either damaging the headphones or my own hearing. I repeated this test with multiple pairs of headphones and IEMs. Zero noise.

The flip side is that when amps have a dead quiet noise floor, they tend to also lack top end power. That is why amplifiers like the Pass HPA-1 sell as well as they do; they somehow manage to combine power, features, resolution, and clarity in a package that is built for the long haul.

The A90 had zero difficulty offering up more than enough power to run the HE6 and HEDD models that are notoriously power hungry regardless of input or output used. The single ended output is capable of 3 watts into 32 ohms and the balanced output can deliver 7.6 watts of power into the same impedance.    

The Topping A90 is a very neutral sounding headphone amplifier that imparts almost no coloration on any pair of headphones connected to it. It does have a personality but it’s the polar opposite of something like the Ampsandsound Kenzie which can be very organic sounding and rolled off with specific headphones.

I love the Ampsandsound headphone amplifiers for the warmth and texture they deliver but to call them accurate would be incorrect. Some users want more body and a different tonal balance with their headphones — the Topping is more like standing on a mountain in the Alps and experiencing a more vivid and clear image of everything.

The A90 grips each pair of headphones with an iron fist and lets you hear absolutely everything on the recording if the headphones are up to the challenge; you can certainly alter the sound with warmer sounding DAC or pair of headphones but the A90’s core focus on power, low noise, and clarity never changes.

The performance for the money is rather remarkable; you could use it with any of the $2,000+ headphones right now and a solid DAC and create a state-of-the-art sounding system.

This is the first sub-$1000 amplifier I would consider as direct competition to amplifiers like the Pass HPA-1 and Benchmark HPA4. It delivers power, resolution, detail, clarity, and one of the quietest backgrounds I’ve ever heard from a desktop headphone amplifier; I was so impressed with it that I considered selling my Pass Labs HPA-1 for the first time and wondered if I would be better off investing the money into a pair of Audeze LCD-5. 

Conclusion

The Topping A90 is an excellent headphone amplifier that is a genuine competitor to far more expensive products from brands like THX, Pass Labs, Schiit Audio, and Benchmark. The A90 is so well designed that it might be the best value below $2,000 which is very high praise.

The A90 often gets overlooked because we focus on the D90/A90 combination and gush over how spectacular the D90 is, but the fact is the A90 may actually be the better product of the two. If Topping would add a remote to the package, it would probably be “best in category” below $2,000.

A huge thank you to Apos Audio for letting us borrow the Topping A90/D90 combo and a set of their Caspian headphones for the weekend.  If you haven’t had a chance to try this combination yet, I highly recommend it.

To purchase a Topping A90, or D90/A90 ensemble, we encourage you to visit our friends at Apos Audio.

Where to buy:

• Topping A90 – $499 at Apos.Audio

• Topping A90/D90 Ensemble – $1,409.99 at Apos.Audio