Pro-Ject
PRO-JECT TUBE BOX S2
Best tube preamp for vinyl enthusiasts seeking a warm, customizable sound.
The PRO-JECT TUBE BOX S2 is a high-end tube phono pre-amplifier designed to deliver a full, relaxed sound with lush mids. It is notable for being the first Pro-Ject product to feature a fully discreet circuit design, completely avoiding operational amplifiers. This unit supports both MM and MC cartridges and allows users to customize the sound signature using replaceable ECC83 tubes. It offers precise RIAA equalization and includes front-panel controls for gain and a subsonic filter. The robust aluminum/metal casing ensures superior sound quality by shielding against vibrations and electromagnetic interference.
$649.99
Owner Satisfaction
4.6
/ 5
Category Rank
303
/ 466
#303 in Phono Preamps
Price vs Category Average
-91%
Below average
Cartridge Support
MM and MC
/ MM and MC
Who it's for
- Space-conscious listeners needing a durable, interference-resistant preamp
- Audiophiles seeking the rich, harmonic character of vacuum tubes
- Vinyl enthusiasts using diverse MM and MC cartridge collections
Who should skip it
- Budget-focused listeners avoiding recurring tube replacement costs
- Minimalists frustrated by bulky external power adapters
- Purists demanding an absolute silent background for low-output cartridges
Performance breakdown
Sonic Character
Delivers the signature lush, warm mids that define high-end tube audio.
Circuit Integrity
Fully discreet design avoids operational amplifiers for a purer signal path.
Cartridge Versatility
Flexible impedance and gain settings accommodate a wide range of cartridges.
Build Quality
Sturdy metal casing effectively shields against unwanted electromagnetic interference.
Customization Potential
Replaceable ECC83 tubes allow for easy, rewarding sound signature experimentation.
Channel Separation
Dual mono circuitry ensures a precise and expansive stereo soundstage.
Key Specs
Cartridge Support
MM and MC
Equalization
Precise RIAA (passive/active, two-part)
Circuit Design
Fully discreet, no OpAmps
Tubes
2x ECC83 (replaceable)
Input Impedance
Five variable settings plus fixed 47k ohms for high output MC
Connectivity
Gold-plated RCA inputs and outputs
Power
External adaptor with multiple internal power supplies and well-filtrated high-voltage anode supply
Construction
Sandwich alu/metal casing
Features
- Fully discreet circuit design, eliminating operational amplifiers (OpAmps)
- Features replaceable ECC83 tubes for sound customization ('tube rolling')
- Offers a full, relaxed sound signature with lush mids, typical of high-end tube pre-amplifiers
- Utilizes dual mono circuitry for optimized channel separation
- Front-sided Gain control for easy adjustment
What customers say
Customers consistently praise the Tube Box S2 for delivering exceptional sound quality, specifically the warm, rich character provided by the tube circuitry. Many reviewers note a significant upgrade in depth and musicality compared to solid state alternatives at similar price points. The unit is frequently highlighted as offering outstanding value for money, making high fidelity tube sound accessible. While the small footprint is appreciated, the extensive adjustability for different cartridges confirms its status as a serious component for vinyl enthusiasts seeking performance without breaking the bank.
Know before you buy
By avoiding operational amplifiers (OpAmps) in favor of a fully discreet circuit, the Tube Box S2 reduces signal distortion and provides a more natural, organic sound. This design choice is a key factor in achieving the warm, lush midrange characteristic of high-end tube audio.
Yes, the Tube Box S2 is compatible with both MM and MC cartridges. It features adjustable input impedance settings, allowing you to fine-tune the electrical loading to match the specific requirements of your cartridge.
Tube rolling refers to the practice of swapping out the factory-installed tubes for different brands or types to subtly alter the sound signature. The Tube Box S2 uses standard ECC83 tubes, making it an excellent platform for users who want to experiment with their system's sonic character.
The front-panel gain control allows you to easily adjust the output level of the preamp to match the sensitivity of your amplifier or active speakers. This ensures you can maintain optimal volume levels and signal-to-noise ratios without needing to reach behind the unit.
The robust metal construction serves two purposes: it provides a rigid, vibration-resistant chassis and acts as a shield against electromagnetic interference. This physical isolation is crucial for keeping the sensitive, low-level signals from your turntable free of unwanted noise.
The subsonic filter is designed to remove ultra-low frequency vibrations, often caused by warped records or turntable rumble. Engaging this filter prevents these inaudible frequencies from overworking your amplifier and speakers, resulting in cleaner, more controlled bass reproduction.
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