In this post, we’ll walk through how the TOPPING D900 and TOPPING D90 III Discrete differ in measurable performance, usability, and engineering design—and where each might fit best in a serious system. If you already know what discrete architectures and balanced pre-amp stages are, this comparison will help clarify the trade-offs between TOPPING’s two flagship approaches.

The D900 is the brand’s newest flagship DAC and pre-amp, built around TOPPING’s proprietary PSRM (Phase-Switching Reference Modulator) 1-bit discrete decoding system. With 32 conversion elements per channel, it delivers ultra-low distortion, exceptional linearity, and a wide ~131 dB signal-to-noise ratio. Bluetooth 5.1 with LDAC and aptX Adaptive adds flexibility, and its pre-amp mode with memory-retained volume control makes it equally at home in desktop or full-size systems.

The D90 III Discrete represents the earlier generation of TOPPING’s PSRM technology—using 16-phase discrete 1-bit modules per channel—and refines it into a reference‐grade DAC with both XLR and RCA outputs, full wired and Bluetooth connectivity, and a high-precision pre-amp mode. It offers performance within a hair of the D900’s, at a lower cost and in a more traditional form factor.

In rough terms:

• The D900 pushes TOPPING’s discrete architecture to its highest measured limits and adds convenience features.

• The D90 III Discrete balances flagship-level transparency with broader compatibility and value.

The D900 uses TOPPING’s latest 1-bit PSRM architecture, comprising 32 discrete switching elements per channel synchronized for ultra-linear conversion. Each channel’s output passes through a custom I/V stage and precision-regulated local supplies. This design eliminates traditional delta-sigma modulation noise while preserving high-frequency linearity and micro-detail. The result is THD+N < 0.000055 % and an SNR of ~131 dB. 

The D90 III Discrete employs TOPPING’s 16-phase PSRM system per channel. Though earlier than the D900’s 32-element implementation, it maintains the same design philosophy: a self‐developed discrete DAC core free of conventional chip-level constraints. It outputs via high-precision I/V conversion and supports pre-amp volume control with memory. 

Both architectures share the same goal — pure 1-bit reconstruction and vanishingly low nonlinearity — but the D900 extends that design with more elements and refined power regulation.

Feature	D900	D90 III Discrete
DAC architecture	32-element PSRM 1-bit discrete	16-phase PSRM 1-bit discrete
Bluetooth	5.1 (LDAC / aptX Adaptive)	5.1 (LDAC / aptX Adaptive)
Preamp / Volume Mode	Digital/analog hybrid with memory	Digital/analog hybrid with memory
Outputs	Balanced XLR + Single-ended RCA	Balanced XLR + Single-ended RCA
Output voltage	~4.0 Vrms (XLR) / ~2.0 Vrms (RCA)	~4.2–5.2 Vrms (XLR) / ~2.1–2.6 Vrms (RCA)
Inputs	USB-B, USB-C, AES, I²S (LVDS), Coaxial, Optical	USB-B, USB-C, AES, I²S (LVDS), Coaxial, Optical
Supported formats	PCM up to 768 kHz / DSD512	PCM up to 768 kHz / DSD512 (native)
Trigger ports	Yes	Yes
PEQ / Tone control	10-band PEQ	10-band PEQ
Network / Streaming	None (external streamer required)	None (external streamer required)

The D900 measures THD+N < 0.000055 % and SNR ~131 dB. The D90 III Discrete comes in just behind, at THD+N < 0.00006 % and SNR ~131 dB. In real-world use, these figures are effectively indistinguishable — both sit far below audible thresholds — but the D900 maintains its distortion profile across a wider range of frequencies and loads due to the expanded PSRM matrix.

The D900’s ~4 Vrms balanced output is suitable for most headphone amplifiers and integrated systems. The D90 III Discrete adds a switchable 4 V / 5 V mode, providing additional headroom for professional or high-impedance amplifiers. Output impedance is specified at 50 Ω (RCA) / 150 Ω (XLR) for the D90 III Discrete. 

Both units include colour OLED displays, solid aluminium remotes, and menu-based configuration. The D90 III Discrete adds EQ, filter, and display adjustments, while the D900 keeps a streamlined interface for pure DAC operation.

• D900: Best suited for listeners who want flagship-level transparency, wireless convenience, and pre-amp functionality in one chassis.
• D90 III Discrete: Ideal for purist, fully balanced chains that benefit from its PEQ, analog-style gain control, and reference-grade noise floor.

• If you want RCA compatibility: Go with the D900—it’s more versatile overall, serving as both a discrete DAC and preamp with wireless and memory-retained volume.
• If your system is fully-balanced and you value value: The D90 III Discrete gives you flagship-level transparency and PEQ tuning at a significantly lower price.
• If you rely on EQ or want fine-grained tone control: The D90 III Discrete has a 10-band PEQ that the D900 also offers, but in a more menu-driven interface.
• If you want the absolute top of TOPPING’s discrete design: The D900 is technically superior—32-element PSRM vs 16-phase, higher-precision regulation, and better preamp behavior—making it the true reference for fully balanced systems and mixed-input setups alike.

• 32-element PSRM discrete 1-bit architecture
• THD+N < 0.000055 % / SNR ~131 dB
• ~4.0 Vrms (XLR) / ~2.0 Vrms (RCA) outputs
• Bluetooth 5.1 (LDAC / aptX Adaptive)
• PCM up to 768 kHz / DSD512
• 10-band PEQ
• Pre-amp mode with memory volume
• Trigger ports
• Price: $1,799 USD

• 16-phase PSRM discrete 1-bit architecture
• THD+N < 0.00006 % / SNR ~131 dB
• Up to ~5.2 Vrms balanced output
• 10-band PEQ + pre-amp mode
• Bluetooth 5.1 (LDAC / aptX Adaptive)
• PCM up to 768 kHz / DSD512 (native)
• Trigger ports and remote control
• Price: $999 USD