Pro-Ject Tube Box S3 B at Vinyl Sound Toronto Canada

The Tube Box S3 B is a balanced audiophile tube phono preamplifier from Pro-Ject Audio Systems (Vienna, Austria), available at Vinyl Sound in Toronto, Canada. Combining the harmonic richness of two ECC83 (12AX7) vacuum tubes with a fully symmetrical and discrete gain stage, balanced 5-pin mini XLR input, and balanced XLR outputs, the Tube Box S3 B brings True Balanced Connection technology to a tube phono stage in an unprecedented way for its price range. Compatible with both moving-magnet and moving-coil cartridges, it offers four gain settings from 40 to 65 dB, five impedance loading options, four capacitance settings, a semi-passive RIAA equalisation stage, and a defeatable subsonic filter, all accessible directly from the front panel. Handmade in Europe since 1991 in a steel and aluminium chassis, it represents the fullest expression of Pro-Ject's True Balanced Connection philosophy in a tube-based design.

ECC83 Tube Amplification and Fully Discrete Symmetrical Gain Stage

At the heart of the Tube Box S3 B is a pair of ECC83 (12AX7) dual-triode vacuum tubes, which form the core of a fully discrete, symmetrical gain stage designed to extract every musical detail from the phono signal while contributing the natural harmonic richness and spatial quality that tube amplification is known for. The gain stage uses no integrated circuits: every component in the amplification path is an individual discrete device, a design approach that is significantly more costly to engineer but results in superior signal integrity, lower noise, and a more lifelike sonic character than op-amp based alternatives. The fully symmetrical circuit architecture processes the positive and negative signal arms independently through matched amplifier sections before recombining them, achieving the noise cancellation and common-mode rejection that balanced transmission provides. A semi-passive RIAA equalisation stage follows the gain stage, maintaining RIAA curve accuracy within 0.4 dB from 20 Hz to 20 kHz.

True Balanced Connection and Front-Panel Cartridge Loading

The Tube Box S3 B is built around Pro-Ject's True Balanced Connection standard, which allows a balanced-ready turntable fitted with a moving-coil cartridge to maintain a fully symmetrical signal path from the stylus through to the balanced XLR outputs. The 5-pin mini XLR input accepts this balanced signal directly, while a standard pair of RCA phono inputs accommodates any conventional single-ended turntable connection. Both inputs can be connected simultaneously, with the active input selected from the front panel and the settings for each stored independently in memory. Cartridge loading adjustments are made entirely from the front panel without dip switches or accessing the interior: five impedance options of 10, 50, 100, 1k, and 47k ohms cover the full range of MC and MM cartridges, four capacitance settings of 50, 150, 300, and 400 pF allow fine-tuning for MM cartridges, and four gain steps of 40, 45, 60, and 65 dB accommodate everything from high-output MM cartridges to the lowest-output MC designs. The XLR output adds an additional 6 dB on top of the selected gain setting. A defeatable subsonic filter at 20 Hz with an 18 dB per octave slope removes low-frequency turntable rumble and warp noise from the signal before it reaches the rest of the system.

Key Features

• 2x ECC83 (12AX7) Vacuum Tubes: A matched pair of ECC83 dual-triode tubes forms the amplification core, delivering the harmonic richness, spatial depth, and musical naturalness associated with the best tube phono stages.
• Fully Discrete and Symmetrical Gain Stage: No integrated circuits in the signal path. Every amplification component is a discrete individual device in a fully symmetrical dual-mono layout for the lowest possible noise and best possible sound quality.
• True Balanced 5-Pin Mini XLR Input: Accepts a fully balanced signal from any Pro-Ject True Balanced Connection turntable, maintaining symmetrical transmission from cartridge to output for maximum noise rejection.
• Balanced XLR Outputs: Full balanced XLR line outputs with an additional 6 dB of gain over the RCA outputs deliver the cleanest possible signal to a balanced preamplifier or integrated amplifier.
• RCA Phono Input and Output: Standard RCA connections accommodate any conventional single-ended turntable and any amplifier with an RCA line input.
• Dual Turntable Connectivity: Two turntables can be connected simultaneously (one balanced, one single-ended), with all loading and gain settings stored independently for each input.
• Front-Panel Cartridge Loading: Impedance (10 to 47k ohms), capacitance (50 to 400 pF), and gain (40 to 65 dB) are all adjustable from clearly labelled front-panel switches with LED indicators, requiring no access to dip switches or the interior.
• Semi-Passive RIAA Equalisation: A semi-passive RIAA stage after the discrete gain stage achieves curve accuracy within 0.4 dB from 20 Hz to 20 kHz for faithful tonal reproduction.
• Defeatable Subsonic Filter: An 18 dB per octave high-pass filter at 20 Hz removes turntable rumble and record warp energy from the signal without affecting the audible frequency range.
• Steel and Aluminium Casework: A rigid steel and aluminium chassis provides structural integrity and electromagnetic shielding for the sensitive tube and phono circuits.
• Memory Storage for Input Settings: All loading and gain parameters are stored in memory for each input, restoring automatically when switching between turntables.
• Handmade in Europe Since 1991: Manufactured by Pro-Ject Audio Systems in Europe with expert craftsmanship and a commitment to long product lifetime and sustainable construction.
• Available in Black or Silver: Two finish options to match any system aesthetic.

Technical Specifications

Connections at a Glance

• Balanced input: 5-pin mini XLR (True Balanced Connection from compatible Pro-Ject turntables)
• Single-ended input: stereo RCA phono pair
• Balanced output: stereo XLR pair (adds 6 dB to selected gain)
• Single-ended output: stereo RCA pair
• Power input: 18V DC (outboard supply included)

Frequently Asked Questions

What is the Pro-Ject Tube Box S3 B?

The Pro-Ject Tube Box S3 B is a balanced tube phono preamplifier from Pro-Ject Audio Systems of Vienna, Austria, supporting both moving-magnet and moving-coil cartridges. It uses two ECC83 (12AX7) vacuum tubes in a fully discrete, symmetrical gain stage with a balanced 5-pin mini XLR input and balanced XLR outputs. Four gain settings from 40 to 65 dB, five impedance options, four capacitance settings, and a defeatable subsonic filter are all adjustable from the front panel. Handmade in Europe, it is designed to bring tube warmth and True Balanced Connection technology to serious vinyl playback at a level of performance previously found only in much more costly phono stages.

How does the Tube Box S3 B compare to the iFi iPhono3 Black Label or Parasound JC 3 Jr.?

The Pro-Ject Tube Box S3 B competes with solid-state phono stages like the iFi iPhono3 Black Label and Parasound JC 3 Jr. but offers a meaningfully different approach. Unlike both of those solid-state designs, the Tube Box S3 B uses ECC83 vacuum tubes in the gain stage, contributing the harmonic texture and three-dimensional soundstage presentation that tube amplification provides. Unlike the iFi iPhono3 Black Label, the Tube Box S3 B includes a balanced 5-pin mini XLR input for True Balanced Connection from a compatible turntable, a feature absent on most phono stages at any price. Compared to the Parasound JC 3 Jr., the Tube Box S3 B offers full front-panel access to cartridge loading adjustments without dip switches, and balanced XLR outputs at a more compact footprint. For listeners seeking tube character alongside balanced architecture and front-panel usability, the Tube Box S3 B stands apart from solid-state alternatives in its category.

What does True Balanced Connection mean for the Tube Box S3 B?

True Balanced Connection is Pro-Ject's system for maintaining a fully symmetrical signal path from the cartridge to the phono preamplifier output. A moving-coil cartridge generates an inherently balanced signal, with a positive and negative conductor for each channel. Using a 5-pin mini XLR cable from a balanced-ready Pro-Ject turntable to the Tube Box S3 B keeps this balanced signal intact all the way into the phono stage. The Tube Box S3 B's fully symmetrical discrete gain stage then processes both signal arms independently before combining them and subtracting any noise introduced along the way. The result is a significantly quieter noise floor, a wider and deeper soundstage, and greater dynamic contrast compared to a conventional single-ended RCA connection through the same circuitry.

Can the Tube Box S3 B be used with any turntable, not just Pro-Ject models?

Yes, the Tube Box S3 B includes a standard pair of RCA phono inputs that accepts the single-ended output of any turntable with a conventional RCA phono cable. The balanced 5-pin mini XLR input is designed for use with Pro-Ject True Balanced Connection turntables and compatible models from other brands that use the same connector standard. Both inputs can be connected simultaneously, with all gain and loading settings stored independently in memory for each. The RCA input delivers the full benefit of the tube gain stage and all front-panel loading adjustments regardless of whether a balanced turntable is used.

Where can I buy the Pro-Ject Tube Box S3 B in Toronto or Canada?

The Pro-Ject Tube Box S3 B is available at Vinyl Sound, an authorised Pro-Ject Audio Systems dealer in Toronto, Canada. Vinyl Sound can advise on cartridge matching, gain and loading settings, and how to integrate the Tube Box S3 B with both balanced and single-ended turntables and amplifiers from any brand.

How do I adjust the gain and loading settings on the Tube Box S3 B?

All cartridge loading and gain adjustments on the Tube Box S3 B are made using front-panel push buttons with LED indicator lights beside each setting. Impedance is selectable at 10, 50, 100, 1k, or 47k ohms for MC and MM cartridges respectively. Capacitance is selectable at 50, 150, 300, or 400 pF for MM cartridge optimisation. Gain is selectable at 40, 45, 60, or 65 dB, with the XLR outputs delivering an additional 6 dB on top of the selected setting. No dip switches, jumpers, or access to the interior of the unit are required. All settings for each input are stored in memory and restored automatically when switching between the two connected turntables.

Are the ECC83 tubes in the Tube Box S3