Pro-Ject Phono Box S3 B


Entry-Level True Balanced Phono Stage

A New Access to High-End Features


The Phono Box S3 B is an entry-level phono preamplifier that offers a fully balanced design in a neat, small package. We’ve packed this tiny chassis to the brim with high-end features. One of those is our new True Balanced Connection. At Pro-Ject, balanced connections were exclusive to our RS range of products until now. The Phono Box S3 B brings those features to an incredible new entry level.

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True High-End For the New Entry-Level

Our Phono Box S3 B comes in complete new casework. The bigger size enabled us to bring a completely new feature set that was never seen before in this price range. The new steel & aluminium case also offers very high rigidity and isolation against outside interferences, which is essential for the new technology inside. Connect up to two turntables simultaneously – all parameters for each input get stored in the memory. You can perfectly match the Phono Box S3 B to a wide variety of cartridges. Use the gain setting to accurately match the output to other sources like CD players or streaming devices. Ultra-low values like 50 pF or 10 ohms allow you to account for all situations.

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Balanced By Nature

Cartridges are balanced signal transducers by nature! Due to the internal wiring of MM cartridges, you’ll need to upgrade your turntable with an MC cartridge to access the entirety of that balanced signal. Together with our new True Balanced Connection cables you’ll be able to access high-end features that were previously only available on the most expensive of phono stages. And the best of all: any Pro-Ject turntable with RCA, miniXLR or 5P outputs can do it!


The new Phono Box S3 B gain stage uses a fully discrete layout. A discrete circuit is composed of disparate electronic components, and individual devices. The amplifier section is built of single parts and doesn‘t use any integrated circuits! That makes for an extended and more costly design process but results in the best sound quality. The fully symmetrical gain stage can optimize the signal-to-noise ratios, feeding the semi-passive, RIAA equalisation stage with a clean signal to work on.


The symmetrical design is the fundamental standout feature! Connect your turntable via the 5-pin mini XLR cable and enjoy the benefits of a balanced signal path. A truly balanced gain stage can extract the final musical information, effectively filtering out any noise from interferences stemming from our noisy, modern homes (household appliances, wifi & Bluetooth, power cables, audio amplifiers).

High-End Features

For the Entry-Level

Steel & aluminium casework. Fully discrete & symmetrical gain stage. Balanced in & outputs. Cartridge loading options on front panel.

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True Balanced

Unleash the full power

Phono Box S3 B is ready for our new True Balanced Connection. Single-ended RCA connections, quite literally, only use half of your cartridge’s output. With one of our new True Balanced phono cables and an MC cartridge you’ll hear details and dynamics, previously exclusive to only the most expensive phono stages.

Truebalancedconnection Logo

Handmade in EU

Since 1991

Made in Europe by technicians, engineers and designers with decades of experience. Expert craftsmanship. Sustainable products with a long lifetime. Audiophile audio performance.


Technical Specifications

Input impedance: 10, 50, 100, 1k, 47k ohms
Input capacitance: 50, 150, 300, 400 pF
Gain (+ 6dB using XLR Out sockets): 40, 45, 60, 65 dB
Signal / Noise ratio MM (40dB): 103dBV, 110dBV – ‘A’ weighted
Signal / Noise ratio MC (60dB): 85dBV, 90dBV – ‘A’ weighted
THD at 1 kHz: <0,001% MM, < 0,005% MC
THD (20Hz-20kHz): <0,008% MM, < 0,01% MC
RIAA-equalization curve accuracy: <0,3dB / 20Hz – 20kHz
Subsonic filter: at 20Hz with 18dB/octave
Input: 1x 5-pin mini XLR / 1x pair RCA phono sockets
Line-level output: 1x pair RCA, 1x pair XLR
Power supply DC: 18V/500mA
Power consumption: 18V/170mA DC, <0.5 W in standby
Dimensions: 206 x 55 x 153 (164 with sockets) mm (W x H x D)
Weight: 930g without power supply


Manual [pdf]


“It sounds cleaner and clearer – especially in fully balanced mode”

UK, 11.2022

• For clarity and soundstage, it doesn’t get any better.





EISA Best Product 2022 – 2023

Earlier this year Pro-Ject launched The True Balanced Technology line for phono reproduction. The benefits clearly convinced the EISA jurors immediately. We hope that in the future the whole industry will adopt True Balanced Connection for phono so more and more vinyl enthusiasts can benefit from it. There has never been a better time to enjoy vinyl records than today.


“S for Satisfying“

UK, 08.2022

• There was no doubt that balanced was superior in every way possible. It just went on and on: background noise reductionopenness, a wider and deeper soundstage.

• What I heard in balanced mode, even with the record deck delivering a single-ended output, elevates this purchase to four-figure levels.

• Immediately apparent, for disarming sceptics, were bottom octave solidity and a greater sense of space.

• What balanced operation did was give the voice greater prominence both in terms of its separation from the backing musicians and in three-dimensional terms, moving it slightly forward.

• What matters is that this sub-£2k package came within a whisker of a revered £40k analogue front-end.


Ken Kessler

“Pro-Ject is really, really onto something here.“

UK, 12.2023

• The S3B is arguably even more convincing.

• This is a pairing that does things that usually cost rather more. 


Ed Selley

“An excellent platform to build an analog playback system with”

USA, 12.2023

• The Pro-Ject Phono Box S3 B phono preamplifier and Pro-Ject X2 B turntable combination produce an engaging and lively sound quality from vinyl records and are built to last.

• And to make them even better, there is a solid upgrade path to get even better sound quality out of both of them.



Gene Hopstetter

“The S3 B is a benchmark product”

USA, 06.2023

• Through the S3 B, the musicians were spread precisely across a wide and deep soundstage that extended well behind the plane of the speakers.
• The sound was so utterly clean and transparent that I almost felt I could reach out and touch it.



Philip Beaudette

Pro-Ject’s bold “True Balanced”- initiative could easily succeed across the board

Germany, 06.2023

• The music emerged as if from a light embrace in that, on the one hand, the spatial spectrum expanded in every direction and at the same time, the reproduction came across as more light-hearted, light-footed, inherently more agile and simply more cheerful.



“Emotionally, I really feel immersed with the completely symmetrical connection of the Phono Box S3 B.“

Germany, 09.2023

• When the “True Balanced” principle is applied front to back, then even more structure, more coherence and a more dynamic agility come into play.



Fritz Schwertfeger

“There is – as mentioned – no competition“

Germany, 10.2022

• A turntable, a special appearance from Ortofon, and the perfect-fit phono amp. Together it becomes magical. The price is still humane, but the sonic gain is great beyond all expectations.




Andreas Günther

“The sound improves significantly with balanced cabling“

Germany, 10.2022

• The symmetrically driven Pro-Ject countered with spirited bass and even more finely articulated treblepowerful, stable and with a warm timbre.


Bernhard Rietschel