TOPPING’s A90 Discrete, also known as the A90D, combines a fully balanced headphone amplifier with preamplifier functionality in a compact desktop component. Priced at $599, it uses four discrete NFCA modules and provides connections for balanced headphones, conventional single-ended models and sensitive in-ear monitors.
Fully discrete NFCA amplifier architecture
The A90D is a redesigned version of TOPPING’s A90 headphone amplifier. Its central change is the adoption of fully discrete components for the NFCA amplifier stage, replacing the earlier implementation with four separate modules arranged as a fully balanced architecture.
Each NFCA module contains 39 transistors, with matched precision devices used to control distortion and noise. TOPPING specifies total harmonic distortion plus noise at less than 0.000055%, alongside a dynamic range of 145dB.
Maximum stated output power is 9,800mW per channel. The combination of high output voltage, high current capability and low output impedance is intended to accommodate a broad selection of headphones, including high-impedance dynamic models, planar-magnetic designs and sensitive in-ear monitors. Two gain settings allow the amplifier’s output behavior to be adapted to different loads.
Balanced and single-ended headphone outputs
Three headphone connections are provided on the front panel. Users can choose between a four-pin XLR output, a 4.4mm balanced socket and a 6.35mm single-ended connection. A 6.35mm-to-3.5mm adapter is included for headphones terminated with a smaller plug.
Volume is managed by an R2R system built from relays and resistor networks. This arrangement is designed to provide precise level adjustment and maintain channel balance across the control range. It also avoids relying on a conventional analog potentiometer for attenuation.
The amplifier can store independent volume levels for its headphone amplifier, preamplifier and combined PRE+HPA operating modes. When an output mode is selected again, the A90D can restore the most recently used setting for that mode.
Preamp mode and system integration
Beyond personal listening, the A90 Discrete can operate as a preamplifier connected to a separate power amplifier. That makes it suitable for integration into a desktop or full-size loudspeaker system as well as a dedicated headphone setup. A supplied remote control allows volume and operating functions to be managed away from the front panel.
A 12V trigger interface supports synchronized power control with compatible components. The connection can be configured as either an active trigger output or a passive trigger input, allowing the A90D to switch on and off alongside another device.
TOPPING has also included a GND/LIFT switch to address ground-loop noise that may arise when several audio components are connected together. Under normal conditions, the switch remains in the GND position. Moving it to LIFT changes the A90D’s grounding point from its chassis to the connected equipment, providing a way to tackle audible hum or buzzing caused by a ground loop.
Finishes, package contents and availability
The TOPPING A90 Discrete is offered in black and silver finishes. The standalone headphone amplifier is listed at $599 and was shown as available at the time of publication.
The package contains the A90D headphone amplifier, remote control, AC power cable, 6.35mm-to-3.5mm adapter, user manual and warranty card. The amplifier is also offered in system packages with a TOPPING D90 III Sabre DAC and a balanced XLR cable. A further package adds an SR2 equipment rack.
These configurations position the A90D as either a self-contained headphone amplifier for an existing source or the control center of a wider TOPPING system. Its preamp output, trigger support and remote operation extend its role beyond headphones without requiring a separate line-level controller.
With its discrete balanced circuitry, three headphone outputs and flexible preamp facilities, the TOPPING A90 Discrete is designed to serve both demanding headphone systems and compact separates-based setups. Its $599 price applies to the standalone amplifier in either black or silver.
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