Pro-Ject Head Box S3 B silver
Pro-Ject Head Box S3 B: fully balanced headphone amplifier
The arrival of this amplifier opens a new generation of the Box Design range from Pro-Ject, whose first components (Micro and Mini) date back to the early 2000s. The Austrian manufacturer returns with two fully balanced models. The Head Box S3 B takes the entry-level position and carries a simple promise: apply a fully balanced architecture at an accessible price, to get more out of the headphones connected at the end of the chain.
A fully balanced topology from end to end
Pro-Ject emphasizes one specific point: many so-called balanced headphone amplifiers are balanced only at the connector level, not in the internal circuit. The Head Box S3 B applies the principle to the entire signal chain, RCA as well as XLR. The signal entering through the Cinch sockets is converted to balanced right at the input and remains processed in differential mode all the way to the outputs. The expected benefits are classic for balanced operation: better rejection of noise picked up along the path, increased separation between left and right channels, and a lower noise floor.
Two TPA6120A2 chips and useful power
The power stage is based on two TPA6120A2 chips from Texas Instruments. The balanced output peaks at 820 mW into 32 Ω, with 480 mW into 8 Ω, 680 mW into 16 Ω, and 320 mW for high-impedance 300 Ω headphones. The manufacturer’s position is clear: rather than chasing advertised watts, it aims for genuinely useful power, the kind that matches the headphones used today. The measured figures point in the same direction. Signal-to-noise ratio greater than 115 dB A-weighted. Total harmonic distortion below 0.002% at 1 kHz for 500 mV input. Crosstalk better than -81 dB at 10 kHz. Frequency response stays within less than -0.25 dB across the entire audible band.
Gain differs depending on the input used: 15 dB in RCA, 9 dB in XLR. The minimum accepted headphone impedance goes down to 8 Ω, which covers nearly all sensitive in-ear monitors, including monitoring models.
Connectivity suited to mixed systems
The rear panel offers one pair of RCA inputs and one pair of XLR inputs, with an RCA loop output (bypass) to connect the device to a speaker amplifier or extend the chain without unplugging anything. The headphone output section is built around four sockets: 4.4 mm Pentaconn and 4-pin XLR in balanced mode, 6.3 mm and 3.5 mm in unbalanced mode. The simultaneous presence of Pentaconn and 4-pin XLR saves high-end headphone owners from needing adapters, since headphones are supplied with one or the other type of wiring depending on the brand.
Aluminum chassis and European manufacturing
The enclosure is made entirely of aluminum, a choice that combines mechanical rigidity with electromagnetic shielding for the internal circuit. The front-panel controls are also machined from the same material. The format remains compact (206 x 55 x 153 mm), and the moderate weight (950 g without power supply) makes installation easy both on a desk and in a hi-fi cabinet. Two finishes are available, silver or black. Production takes place in Europe.
The external 18 V DC power supply, included with the device, accepts 110-240 V and limits standby consumption to less than 0.5 W. Moving the power supply outside the main chassis is a common Pro-Ject practice to keep stray radiation away from the audio circuit.
Documentation
Technical Specifications
Topology and power stage
- Brand-new fully balanced headphone amplifier topology
- Power stage implemented with two TPA6120A2 chips for rich sound
- Fully balanced signal path for RCA and XLR inputs
- Balanced output power up to 820 mW
- Redefines the category of balanced headphone amplifiers in its price range
Audio performance
- Maximum output power:
- 480 mW at 8 Ω
- 680 mW at 16 Ω
- 820 mW at 32 Ω
- 320 mW at 300 Ω
- Signal-to-noise ratio: > 115 dB A-weighted at 1 kHz
- Total harmonic distortion: < 0.002% at 1 kHz for 500 mV input
- Crosstalk: < -81 dB at 10 kHz
- Gain: 15 dB (RCA input) / 9 dB (XLR input)
- Frequency response: < -0.25 dB from 20 Hz to 20 kHz
- Minimum headphone impedance: 8 Ω
Connectivity
- Balanced headphone outputs: 4.4 mm Pentaconn, 4-pin XLR
- Unbalanced headphone outputs: 3.5 mm, 6.3 mm
- Analog inputs: 1 pair RCA / Cinch, 1 pair XLR
- Analog loop-through outputs (bypass): 1 pair RCA, for connecting an additional amplifier or expanding the system
Construction and finish
- Fully aluminum chassis of superior quality ensuring mechanical stability and effective shielding
- Controls and buttons made of high-quality aluminum
- Available in silver or black
Power supply and consumption
- Power supply: 18 V / 1 A DC, 110-240 V, 50 / 60 Hz
- Standby power consumption: < 0.5 W
Dimensions and weight
- Dimensions (W x H x D): 206 x 55 x 153 (170) mm
- Weight: 950 g excluding power supply
Frequently Asked Questions
Does the Head Box S3 B replace an older model?
It launches a new generation of the Box Design range, whose first components (Micro and Mini) date back to the early 2000s. Rather than a direct replacement for one specific model, its arrival (along with the DS3 B above it) marks a complete renewal of the architecture, now centered on full signal symmetry.
What is the difference compared with the Head Box DS3 B?
The DS3 B moves to a fully discrete topology (with no integrated circuit in the amplification stage) and delivers 1.5 W into 32 Ω, nearly double the power. It is larger and provides the headroom needed for headphones that are difficult to drive, such as certain low-sensitivity planar magnetic models.
Is a balanced-wired headphone mandatory?
No. The two unbalanced outputs (3.5 mm and 6.3 mm) remain available and benefit from the same signal chain. Going balanced brings a measurable gain in channel separation and background noise, but the S3 B remains fully worthwhile with a traditional 6.3 mm jack headphone.
What is the RCA loop output on the back for?
This output takes the RCA input signal without processing and sends it to another device, for example an integrated amplifier driving speakers. It avoids having to unplug the source every time you switch listening modes (headphones or speakers) and simplifies integration into an existing hi-fi system.
Is the gain switchable?
Gain depends on the input used, but there is no dedicated switch: 15 dB for the RCA input, 9 dB for the XLR input. The choice of input therefore determines the available gain level. This difference is consistent with the higher level delivered by a source with a balanced XLR output.
Which headphones can it drive properly?
The range is wide. The minimum accepted impedance goes down to 8 Ω, and 320 mW remain available into 300 Ω for high-impedance headphones. Medium-sensitivity dynamic models, 32 to 80 ohm headphones, classic 250 and 300 ohm models, and sensitive in-ear monitors all have comfortable headroom.
Can it be used as a preamplifier for active speakers?
Not directly. The RCA loop output is a bypass, its level is not controlled by the volume potentiometer, and there is no variable preamp output. To drive an active speaker system from the same volume control as the headphones, another component in the chain is required.
- Eco-contribution of €0.12 included in the sale price.
- GTIN / EAN: 9120137901306
