The Problem: Mains Noise in Your Phono Signal
A phono signal is tiny — the cartridge output is measured in millivolts. Any noise riding on the power supply gets amplified right along with the music, turning AC hum, RFI, and switching noise into a background haze that smears imaging and masks detail.
If you hear a low hum from your speakers or notice a lack of space around instruments, your turntable's power supply might be the culprit. The typical wall-wart or switching supply passes along mains-borne interference that a sensitive phono stage can't ignore.
How the Accu Box S2 Fixes It
- Pro-Ject Accu Box S2 Battery Power Supply - Silver: The Accu Box S2 runs your phono electronics on pure battery power—five cells of rechargeable Li-Pol batteries with a 2.6Ah capacity—so hum, RFI, and mains-borne interference simply never enter the signal. Battery power physically breaks the connection to the AC mains, eliminating the noise path entirely. No filtering or conditioning can match a complete disconnection.
Pro-Ject Accu Box S2 Battery Power Supply - Silver
What You'll Hear
With a delicate phono signal, the difference is immediate: a more homogeneous, spacious sound with better separation, imaging, and a cleaned-up, relaxed presentation. Battery power removes the AC mains from the equation entirely — revealing quieter backgrounds, better separation and imaging, and a more spacious, natural sound.
This isn't a subtle tweak. If your current power supply is injecting noise, switching to battery power can feel like lifting a veil from your system.
Which Components Does It Power?
The Accu Box S2 provides two outputs: an 18V/1A (2.5mm) for Pro-Ject phono preamps and electronics, plus a 5V/1A USB A output for DACs, headphone amps, and other digital components. Pro-Ject lists the following as compatible:
- S-Line: Stream Box S2, Stream Box S2 Ultra, BT Box S2, Pre Box S2 Digital, Pre Box S2 Analogue, DAC Box S2 +, Head Box S2, Head Box S2 Digital, Tube Box S2, Phono Box S2, Phono Box S2 Ultra, Phono Box S3 B, and Vinyl NRS Box S3.
- E-Line: Optical Box E, Phono Box E, Phono Box E BT, and Record Box E.
- DS-Line: Phono Box DS2, Phono Box DS2 USB, Tube Box DS2, Tube Box DS3 B, Phono Box DS3 B, DAC Box DS2 Ultra, Pre Box DS2 Digital, Pre Box DS2 Analogue, Head Box DS2 B, and CD Box DS3.
Can It Power Your Pro-Ject Turntable?
Yes, with the optional Pro-Ject Connect-It 18V/15V 2.5-2.1mm cable (sold separately), the Accu Box S2 can power most Pro-Ject turntables as well. Check your turntable's voltage and connector type before ordering.
Practical Considerations
- Battery life: A full charge takes about three hours and delivers roughly 6.5 hours of playback. Built-in over-charge, over-discharge, and over-current protection safeguards the batteries for maximum lifespan.
- Size and placement: Housed in full aluminum/metal casework just 4 inches wide, the Accu Box S2 tucks in anywhere. Choose black or silver to match your Pro-Ject stack.
- Control and status: A front-panel push button enables or disables both rear outputs, with an LED confirming status and charging.
Is It Right for Your System?
The Accu Box S2 is a targeted solution for AC hum and noise in a phono or line-level signal path. If you don't hear noise from your current supply, you may not notice a dramatic change. But if you suspect power quality is holding back your system, this is one of the most direct ways to test that theory — without buying a full power conditioner.
Because it's a battery supply, it also offers temporary off-grid use for setups where mains power is inconvenient or noisy.
