miniDSP Flex HPA DSP Headphone Amplifier

A headphone amplifier with a DSP engine behind it

The miniDSP Flex HPA brings a high-power headphone amplifier to miniDSP’s Flex platform. A DAC, a 400 MHz SHARC DSP and a balanced headphone stage share one compact desktop chassis, so the same unit can EQ your headphones, drive a pair of active monitors and integrate a subwoofer.

It has the same digital inputs as the Flex: USB Audio, coaxial and optical S/PDIF, and Bluetooth with LDAC, aptX HD, aptX, AAC and SBC. Two balanced TRS inputs add an analogue source, and four balanced TRS outputs on the rear connect to active speakers, power amplifiers or subwoofers. The Flex HPA joins the Flex and Flex Eight in miniDSP’s Flex series.

Power and control for any headphone

The front panel has a balanced 4-pin XLR output and a single-ended 6.35 mm jack. In balanced mode, the Flex HPA delivers up to 5.2 W per channel into 50 Ω, 4.4 W into 32 Ω and 0.87 W into 300 Ω. The single-ended output reaches 5.2 W into 12 Ω, which suits low-impedance designs. Output impedance is below 0.4 Ω balanced and 0.2 Ω single-ended.

Five gain settings, from -3 dB to +12 dB, let you match the amplifier to anything from sensitive in-ear monitors to inefficient planar magnetic headphones. Measured distortion is -117 dB THD+N (0.00014%) into 300 Ω, and DC detection and temperature monitoring protect both your headphones and the amplifier.

Tune the sound, not just the volume

Every output has parametric EQ, IIR and FIR filtering, crossovers, advanced biquad programming and delay, configured in the miniDSP Device Console app. The DSP runs at 32-bit / 96 kHz, or 32-bit / 48 kHz with Dirac Live installed. The headphone amplifier is fed from DSP channels 3 and 4, which also appear on rear outputs 3 and 4. Outputs 1 and 2 are processed independently, so you can apply a headphone correction curve without affecting your speakers.

Four presets let you keep separate settings for different headphones or for your speakers. For speakers in a real room, optional stereo Dirac Live 3.x provides full-range correction from 20 Hz to 20 kHz, measured with a calibrated UMIK-1 or UMIK-2 microphone.

On the desk, in the studio, in the living room

Day-to-day control comes from the front-panel OLED display and volume knob, or the supplied IR remote. The Flex HPA also works with miniDSP’s KD-1 smart remote for tactile desktop control. Trigger input and output on 3.5 mm jacks let it switch other components, or be switched by them.

USB is bidirectional, returning four post-DSP channels to your computer, which is useful for recording and measurement. That flexibility makes the Flex HPA a complete desktop system, a monitoring hub for a home studio, or a headphone and DSP upgrade for a two-channel hi-fi system.

Features

Specifications

Brand	miniDSP
Colour	Black
Audio Inputs	1 x Bluetooth, 1 x coaxial digital RCA, 1 x optical Toslink, 1 x USB, 2 x balanced TRS
Audio Outputs	4 x balanced TRS, 1 x 4-pin XLR headphone, 1 x 6.35 mm headphone
Bluetooth Codecs	LDAC, aptX HD, aptX, AAC, SBC
Headphone Power	Balanced: 5.2 W x 2 (50 Ω), 4.4 W x 2 (32 Ω), 0.87 W x 2 (300 Ω); single-ended: 5.2 W x 2 (12 Ω), 2.0 W x 2 (32 Ω), 0.22 W x 2 (300 Ω); all at <1% THD+N
Headphone Output Impedance	<0.4 Ω (balanced), <0.2 Ω (single-ended)
Headphone Gain	-3 dB, 0 dB, +6 dB, +9 dB, +12 dB
Signal-to-Noise Ratio	126 dB(A) (line outputs), 124 dB(A) (balanced headphone, +12 dB gain)
Distortion	0.0001% (line outputs), 0.00014% (headphone, 300 Ω, +12 dB gain)
Frequency Response	20 Hz – 20 kHz (±0.1 dB)
DSP	400 MHz Analog Devices SHARC DSP
Room Correction	Dirac Live 3.x (optional upgrade)
Display	White OLED display
Power Consumption	17 W (amplifier on), 8.6 W (amplifier off), 0.4 W (standby)
Dimensions (W x D x H)	214.5 mm x 205 mm x 41.5 mm

What’s in the box?

• miniDSP Flex HPA
• IR remote control
• 12 V universal power supply with UK, EU, US and AU plugs
• USB cable

Downloads

• Flex HPA product brief
• Flex HPA user manual
• Flex HPA user manual (Dirac Live version)