Unitra WSH-605 silver

The WSH-605 is a 70-watt under 8 ohms stereo integrated amplifier developed by Unitra, a Polish manufacturer. It features patented gain error correction technology and an ESS Sabre digital-to-analog converter. Designed in Poland, it adopts a modular architecture that accommodates both analog and digital sources.

Metal construction and retro touch controls

The WSH-605’s all-metal chassis reflects a robust build designed to last for decades. The brushed aluminum front panel, available in silver or black, gives the unit a discreet yet confident presence. Its compact dimensions (440 mm wide, 372 mm deep, 104 mm high) make it easy to integrate into any hi-fi rack, while the 11.8 kg weight ensures perfect stability even when operating the controls.

Four substantial rotary knobs grace the front: volume, balance, bass, and treble. Their generous diameter and smooth travel allow fine adjustments, particularly appreciable for volume thanks to a high-precision potentiometer. Two 1970s-style toggle switches complete the interface: one selects sources, the other activates the “contour” function, which disables the tone controls for a direct signal.

The 6.3 mm front-panel headphone jack feeds a dedicated low-output-impedance amplifier, designed specifically for high-end headphones. This independent section delivers enough power to drive models that are particularly demanding in terms of impedance and sensitivity. Plugging in headphones automatically cuts the speaker outputs, avoiding any extra steps.

Gain error correction technology: an unconventional approach

The WSH-605’s amplification section is based on gain error correction implemented directly in the power stage—an approach rarely seen in commercial audio designs. Unlike traditional negative feedback circuits that attempt to correct distortion after the fact, this system continuously compares the signal after the output stage with the signal at its input, then reinjects the calculated difference at the input.

This global correction precisely compensates for different types of distortion throughout the entire signal path. The result is a total harmonic distortion of just 0.0013% at 1 watt, 1 kHz, and intermodulation distortion below 0.0005% on the standard 19+20 kHz test. These exceptionally low figures ensure crystal-clear sound reproduction, preserving micro-details and the harmonic texture of recordings.

Class AB amplification delivers 70 watts RMS into 8 ohms and 110 watts into 4 ohms, providing comfortable power reserves for most loudspeakers on the market. Frequency response extends from 7 Hz to 75 kHz, well beyond the audible spectrum, ensuring linear phase within the useful bandwidth. A 108.8 dB signal-to-noise ratio guarantees a remarkably quiet background, even at low listening levels.

ESS Sabre DAC and digital source management

The built-in ESS Sabre digital-to-analog converter is one of the WSH-605’s key strengths. Renowned in the industry for its outstanding performance, this chip integrates advanced jitter reduction that stabilizes the digital signal—even when it comes from consumer gear such as TVs or set-top boxes that typically generate higher jitter.

The DAC accepts PCM signals up to 192 kHz/24-bit, covering the full range of hi‑res formats available on streaming platforms and current physical media. Two coaxial and two optical inputs allow multiple digital sources to be connected simultaneously: CD player, TV, game console, network streamer, or computer. Source switching is handled via the front rotary selector, with automatic recall of the last used source.

ESS’s patented HyperStream technology pushes modulation noise out of the audio band, preserving the soundstage in all its purity and spatial coherence. This architecture also achieves a flat noise floor up to 200 kHz, a sought-after characteristic for natural reproduction of transients and upper harmonics.

Preamplification section and built-in phono stage

The WSH-605’s preamplification section includes a dedicated phono stage for moving-magnet (MM) cartridges, enabling direct connection of a turntable without an external preamp. The ground post adjacent to the phono input provides effective equipotential bonding with the turntable’s chassis, minimizing hum. The RIAA circuit applies the standard de-emphasis curve with precision, restoring the original tonal balance of the recordings.

Internal connections between the rear-panel inputs and the front-panel potentiometers use a symmetrical configuration. This differential architecture effectively rejects electromagnetic interference and common-mode noise that can couple onto internal runs, particularly in urban environments saturated with radio waves and electrical disturbances.

Five line inputs accommodate traditional analog sources: tuner, network player, CD player, VCR, or any other line-level device. A variable preamplifier output allows the addition of an external power amplifier or an active subwoofer, with volume, tone, and balance functions remaining active on this output. This flexibility enables progressive system upgrades without replacing the main amplifier.

Remote control and everyday ergonomics

The included remote control provides essential functions from the listening position: volume adjustment, mute, source selection, and standby. A particularly well-thought-out “linear” button lets you enable or disable tone corrections remotely, making instant comparisons between the direct and corrected signals easy. This proves valuable when assessing the impact of tone settings on different recordings.

Volume adjusts in fine steps for precise level control. The mute function instantly silences both speakers and headphones—handy during phone calls or to preserve the neighbors’ peace. Standby reduces power consumption while keeping control circuits powered for instant wake-up.

High-quality speaker terminals accept banana plugs, spade lugs, or bare wire. Their generous spacing simplifies connection of large-gauge cables, while progressive tightening ensures optimal electrical contact without risking damage to conductors. The clear, color-coded layout (red for positive, black for negative) helps avoid potentially harmful wiring errors.

Technical Specifications

Power and audio performance

• Continuous power: 70 W / 8 Ω, 110 W / 4 Ω
• Frequency response: 7 Hz – 75 kHz
• Signal-to-noise ratio: 108.8 dB
• Channel separation: > 75 dB @ 1 kHz
• Total harmonic distortion: 0.0013% @ 1 W, 1 kHz
• Intermodulation distortion: < 0.0005% (19 + 20 kHz, 1:1)
• Dynamic, natural-sounding Class AB amplification

Digital conversion and signal processing

• Built-in ESS Sabre digital-to-analog converter (DAC)
  • Precise digital-to-analog conversion
  • Advanced jitter reduction
  • Compatible with TVs and set-top boxes
• Advanced error-correction technology
  • Low harmonic distortion
  • Minimal intermodulation

Connectivity and inputs/outputs

• Analog inputs: AUX, tuner, network streamer, CD, phono + ground (moving magnet)
• Digital inputs: 2 coaxial, 2 optical
• Outputs: speaker terminals, preamp output, 6.3 mm headphone jack
• Symmetrical signal paths between inputs and potentiometers to reduce interference

Controls and adjustments

• Precise volume, balance, and tone controls
• Audio adjustments: bass, treble, contour (tone control bypass), balance
• Integrated source selector
• Built-in moving-magnet phono stage
• Low-impedance headphone amplifier for high-end headphones

Physical characteristics

• Dimensions (W × D × H): 440 × 372 × 104 mm
• Weight: 11.8 kg
• Metal chassis with brushed aluminum front panel
• Sturdy knobs and retro-style switches