I have covered the topping D90SE quite extensively, which is one of my favorite affordable DACs in this category. It’s very well designed and sounds great. The topping A90 has ever been able to slip through my fingers. It uses the same chassis as the D90 and works well with it, but it’s worth considering outside the Topping ecosystem.
Topping is a Chinese audio maker that manufactures a wide range of DACs and amplifiers, from the $ 100 price range to the $ 1400 D90 / A90 pairing. The toppings are ASR’s beloved and their products have been so well tested that the D90 / A90 combo (pictured above) has received a lot of attention and lent us a combination for use in THE Show. He was a good seller of Apos Audio. Topping did not design the circuit used in the A90, a nested feedback composite amplifier design, but has come a long way to complete it.
Design & build
The A90 uses an all-aluminum chassis available in either a brushed draw finish or anodized flat black. It is 2 inches high, 9 inches wide, and about 6 inches deep. It’s the same chassis shared by the D90 and U90 models, so it stacks neatly for use on smaller desktops. If you’re new to the U90, it’s a USB interface model and a great USB-coaxial or optical converter.
On the front, there is a series of three switches on the left, a headphone port (XLR and 4.4mm balanced, 6.35mm single end) in the center, and a volume knob on the right. The first switch acts as a power switch, putting the A90 in either preamp mode or headphone amp mode, depending on the location. The second switch selects either an XLR or RCA input, and the third switch controls the gain level of the amplifier. All the controls you need are easily accessible through the front panel, which is always a plus. It does not provide the best remote control for later models, especially when used as a preamp.
On the back, there are two pairs of XLR jacks and two pairs of RCA, each for input and output. Remember that the input jack is selected on the front panel so that you can always connect both sources. This allows the A90 to effectively act as a small preamp for two source devices.
internal
As mentioned above, the A90 uses a nested feedback design. This means that the A90 uses a cascade op amp in combination with a negative feedback loop that helps control each op amp. The way this works is that the 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 to the next op amp. The result is an amplifier with higher gain, faster slew rate, and less distortion than an amplifier that uses the same op amp in parallel. There are some hurdles to consider when working with composite designs. The main one is much higher output resistance than other designs. Topping handles this problem well and the output impedance is very low. Another problem is that the negative feedback design usually has low gain, but again, the output power is close to 8 watts (balanced in, balanced out), so the A90 doesn’t lose power either. Topping has gone as far as to challenge THX and its marketing campaigns. The A90 actually measured at least as well as most THX implementations and beat many of them in tests with toppings, ASR, Soundguys and more.
As a preamp, it can output up to 18 V at low gains and up to 49 V at medium and high gain settings, so it can drive almost any headphone you can think of, and works well with almost any powered monitor. Come to think of it, it has enough power in most cases (even at low gain).
Looking at the A90’s spec sheet, you can see that the toppings weren’t shot to make a good budget amp. They were shooting to make great amps regardless of price, and the numbers suggest they were successful. But the numbers aren’t everything, and unless it sounds good, the numbers aren’t anything.
sound
The first thing I noticed with the A90 was that it was easy to handle all the headphones I connected. From in-year to He6, I didn’t feel any stress. Instead, taking what you gave with a stride and putting the gain switch in the right position made it quiet enough to use Andromeda, but powerful enough to hurt your hearing. He6 provides almost any headphone settings you may encounter.
In most cases, one of the noisy tests is to pause the music, turn up the volume knob all the way up, and listen to hum and hiss. Andromeda is known to have hiss noise in most desktop amp setups, so I set the A90 to low gain and started listening at about 9:30 on the dial, but this So far there is no hiss noise. You need to turn the volume up to 11 o’clock and make it loud enough and short, but there is still no hiss. Pauses the track and cuts the volume knob completely, but there is no hiss noise yet. Perhaps my hearing is poor? I retried the test with the same results at medium and high gains. The A90 has a huge SNR and you may not have been able to make Andromeda malfunction, so give it a try.
Conversely, if your amplifier has a quiet noise floor, it also tends to lack top-end power. That’s why things like the Pass HPA-1 sell just as they do. They could somehow combine both features, and to be honest, they were in the price range you had to buy to buy both. The A90 had no problem providing enough power to run the He6 and Hedd models, which are famous for their high power consumption, regardless of the input or output used. The single-ended output is 32Ω and has a capacity of 3 watts, and the balanced output is a whopping 7.6 watts with the same load.
This combination of vanishing noise and great power allows the A90 to operate over many dynamic ranges and be visible when listening. Quiet passages are almost quiet and crescendos are thunder. The boom meant loose, and it wasn’t, so I struggled with the words there. The A90 provides a very transparent sound with little or no color and no slack, even with repeated heavy shocks that can squeeze the amp. As I said at the beginning, the A90 can easily handle everything that can be thrown, regardless of the source or headphones connected, making music playback easy to see.
This is the first amp I think is less than $ 1000 that directly competes with amps like the PassHPA-1 and Benchmark HPA4. It really worked very well and I saw the pass and thought it was time to sell it and invest money in the LCD-5.
Conclusion
The Topping A90 is one hellova headphone amp for spending and you have to worry of course for THX, Pass, Benchmark, and other manufacturers who are charging more for less amps. .. Sure, the Prestige brand continues to win customers whose name is as important as sound, but savvy car buyers are a better investment than the Lamborghini Aventador in terms of pure performance for the Z06 Corvette. As you know, the A90 may need a better amp, and as well as a car comparison, the A90 may need less maintenance.
The A90 is often overlooked when looking at the D90 / A90 combo and seeing how spectacular the D90 is, but in reality the A90 may be the better of the two products. If the topping adds a remote control to the package, it’s almost perfect.
A big thank you to Apos Audio for letting me borrow a topping A90 / D90 combo and a set of Caspian headphones over the weekend. If you haven’t had a chance to try this combination yet, we highly recommend it. Listen to Vivaldi’s concerto in 2 Cellos in G minor to see the possibilities of this combination.
To buy a topping A90 or D90 / A90 ensemble, we recommend visiting a friend of Apos Audio.
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