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Pro-Ject Phono Box S3 B Phono preamplifier for moving magnet and moving coil cartridges (Black)

Item # 252PHS3BBK

It offers plenty of cartridge-loading flexibility for vinyl listeners who want to get the most out of their turntable.

It offers plenty of cartridge-loading flexibility for vinyl listeners who want to get the most out of their turntable.

Item # 252PHS3BBK

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In stock
$499.00

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About the Pro-Ject Phono Box S3 B

Eric A.

Product highlights:

  • compatible with moving magnet and moving coil phono cartridges
  • discrete audio circuitry in a full dual mono configuration for optimal channel separation and clarity
  • true balanced gain stage for reduced channel noise and enhanced detail when using compatible turntables with balanced output
  • subsonic filter reduces low-frequency rumble and wasted amplifier power (18dB/octave at 20 Hz)
  • steel and aluminum chassis shields audio circuitry from vibration and electromagnetic interference
Performance specs:
  • input impedance: 10, 50, 100, 1k, or 47k ohms
  • capacitance settings: 50pF, 150pF, 300pF, or 400pF
  • gain settings: 40dB, 45dB, 60dB, and 65dB
  • RIAA response accuracy: 0.3dB (20-20,000 Hz)
  • THD (20-20,000 Hz): 0.008% (MM); 0.01% (MC)
  • signal-to-noise ratio: 103 dBV (MM); 85 dBV (MC)
Connections:
  • unbalanced stereo RCA input and output
  • 5-pin mini XLR balanced stereo input
  • pair of standard XLR balanced outputs
  • 12-volt trigger input and output
Dimensions and warranty:
  • 8-1/8"W x 2-3/16"H x 7-1/8"D
  • weight: 2.05 lbs.
  • warranty: 2 years
  • MFR # 9120097829283
  • Item # 252PHS3BBK

What's in the box:

Pro-Ject Phono Box S3 B owner's manual

If you need assistance accessing this owner's manual, please give us a call.
  • Phono (MM/MC) pre-amplifier
  • AC power adapter (with attached 4' DC cord)
  • 3 AC power plug iinserts (US/EU/UK)
  • Instructions For Use

More details on the Pro-Ject Phono Box S3 B

Stacey B.

Features & specs

Features
Cartridge Type MM, MC
Subsonic Filter Yes
Cartridge Loading Selectable
Adjustable Resistance Load Yes
Adjustable Capacitance Load Yes
Vacuum Tube No
Connections
RCA Inputs 1 Pair
XLR Inputs No
RCA Output 1 Pair
XLR Output Yes
USB Output No
3.5mm Output No
Optical Output No
Coaxial Output No
Specs
Signal-to-noise Ratio (MM) 103
Signal-to-noise Ratio (MC) 85

Product Research

Features

True Balanced Design: The Pro-Ject Phono Box S3 B features a "True Balanced Design" that can now extract the final musical information out of the audio signals, plus subtract and remove all noise that could potentially be added along the transmission. It features a fully discrete & symmetrical gain stage with balanced input and outputs for dynamic and detailed sound from your vinyl record collection.

  • Fully Discrete Gain Stage: The gain stage of the new Phono Box S3 B uses a fully discrete layout. A discrete circuit is composed of electronic components which are differing, individual devices. The amplifier section is built out of single components and doesn't use any integrated circuits for better results when it comes to sound quality.
  • Semi-Passive EQ: After treating the balanced audio signals independently, they are added back together and are processed by the semi-passive RIAA equalization stage. By keeping the gain stage fully symmetrical, the Phono Box S3 B can optimize the signal-to-noise ratio and keep interference to a minimum. For the balanced XLR outputs, a balancing stage generates a symmetrical signal, so you benefit from balanced signal transmissions again.

Note: The Phono Box S3 B is compatible with MM (moving magnet) and MC (moving coil) cartridges. However, 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 audio signal. 

Balanced & Unbalanced Connectivity: The Pro-Ject Phono Box S3 B is outfitted with balanced (XLR) and unbalanced (RCA) connection. There is stereo unbalanced RCA input, plus a 5-pin mini XLR balanced stereo input to connect to your turntable. There is also a stereo unbalanced RCA output, as well as a XLR balanced stereo output to connect to the corresponding unbalanced or balanced line-level input of your integrated amplifier or AV receiver. By utilizing phono preamp's 5-pin mini XLR input and stereo XLR outputs, you'll enjoy the benefits of a balanced signal path.

Note: A 5-pin mini XLR to stereo RCA cable (sold separately) is required to make connection between the Phono Box S3 B's 5-pin mini XLR input and the stereo RCA output of your turntable.

Control Settings: The Phono Box S3 B features various control settings to perfectly match the Phono Box S3 B to a wide variety of phono cartridges, making sure your turntable sounds it best.

  • Gain Levels: The phono preamp's gain level (40/45/60/65dB) can be adjusted to match the level of your MM/MC turntable.
  • Input Impedance/Capacitance: You can adjust the phono preamp's input impedance (10/50/100/1k/47k Ohms) and input capacitance (50/150/300/400 pF) to the setting that best suits your turntable.
  • Subsonic Filter: A switchable subsonic filter prevents your amplifier and speakers of ultra low rumble below 20Hz (-18dB).

Note: You can connect a up to two turntables simultaneously (one via balanced and one via unbalanced), with all the control settings and parameters for each input stored in the phono box's memory.

Ground Terminal: The phono preamp also has a turntable ground, in case your turntable has a separate ground lead. This provides shielding to the tone-arm and the sensitive circuitry in the turntable.

External Power Supply: The Phono Box S3 B is powered by an external AC adapter in order to keep all the parts which can radiate electromagnetic fields out of the phono preamp's amplifier range.

All Metal Case: The Phono Box S3 B's steel & aluminum case offers very high rigidity and isolation against outside interferences, which is essential for phono applications. The front-panel push button controls are also made from aluminum. The Phono Box S3 B is available in a black or silver finish.

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Customer Q&A

2 questions already asked

Q
Is this compatible with a Pro-Ject X2 (original version), assuming I have the correct connectors? And, will sound benefit? I use an MM cartridge (Ortofon Black).
mark  Jan 20, 2024
1 answer
A
Greetings Mark. Thank you for your question. It is compatible with your X2, and cartridge to some extent. The older version X2 did not have the balanced XLR out, so you would use the normal unbalanced RCA. Unless you in the future upgrade the TT to one that have XLR out, and also had XLR in on your integrated amp I would look at a more affordable preamp that does not have the extra cost of XLR inputs/outputs.
thomas  Jan 20, 2024 (Staff)
Q
I have a Pro-Ject X1B with mini XLR output. My AVR (Yamaha RX-A4A) does not have XLR inputs. Is there any benefit of running mini XLR from the turntable to preamp if I'll be running RCA cables from the preamp to the AVR?
christopher  Jan 27, 2025
1 answer
A
Greetings Chris. Thank you for your question. For a balanced output to do its main job, there has to be a balanced input on the receiving unit. Using an adapter, you would not be getting the noise reduction capabilities of the balanced connection, however XLR output does have a stronger voltage output than an RCA output. You should have at least more signal voltage into your Yamaha. Using a better phono stage from an external phono preamp will be beneficial as well.
thomas  Jan 27, 2025 (Staff)

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Additional cartridge-loading flexibility and improved performance

The Pro-Ject Phono Box DS3 B offers these features:
  • front-panel input-impedance control for low-output moving coil cartridges
  • switchable loading: continuously variable from 10-1000 ohms or fixed 47k
  • additional gain settings of 50dB and 55dB
  • RIAA response accuracy: 0.25dB (20-20,000 Hz)
  • THD (20-20,000 Hz): 0.005% (MM)
  • signal-to-noise ratio: 104 dBV (MM)
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