Review · Editor's Choice

Pro-Ject Power Box S3 Phono Filter Review

If you own a compatible Pro-Ject stage and the rest of your chain is already sorted, I think this is a sensible refinement upgrade. It won’t remake your system, but it can lower the noise floor enough to make quiet listening feel cleaner.

Last updated September 21, 2026 · By Marcus Webb
Check price on Amazon → $249.00
Pro-Ject Power Box S3 Phono Filter

In this review

Darkside Vinyl is reader-supported. When you buy through links on our site we may earn an affiliate commission, at no extra cost to you. It never changes our verdict or our score. How we make money.

Darkside Vinyl's verdict

If you own a compatible Pro-Ject stage and the rest of your chain is already sorted, I think this is a sensible refineme
4.5 / 5
4.5 out of 5
Pro-Ject Power Box S3 Phono Filter Pro-Ject Power Box S3 Phono Filter

I'd buy it for a Phono Box S3 or Phono Box DS3 B in a revealing system with passive speakers or headphones. I wouldn't buy it to fix obvious hum, ground loop issues, or noise from a basic powered-speaker setup.

In a good system, the change is usually simple: the tonal balance stays about the same, but the space between notes feels calmer. That's the kind of upgrade you notice more at 11 p.m. than at noon.

Pros

  • Ultra stable power
  • Low noise output
  • Rigid aluminium casing
  • Effective voltage regulation

Cons

  • Higher price point
  • Requires careful placement
  • Limited to specific setups

Our best deal today

$249.00 from Amazon

Price checked today · free returns

Get the Pro-Ject Power Box S3 Phono Filter →

At a glance

Pro-Ject Power Box S3 Phono Filter, by the numbers

The specs and scores that matter most when deciding if this product fits your setup.

Our score 4.5 / 5
Price $249.00
Store Amazon
Category Uncategorized

How it scored

4.5 / 5 overall
Sound Quality 4.7
Build Quality 4.5
Ease of Setup 4.2
Features 3.9
Upgradeability 4.3
Value 4.6

Get the full picture

What everyone else is saying

Our take set against the consensus from owners and the wider vinyl community.

M
Marcus Webb
Our reviewer

I like this kind of upgrade when the system is already honest enough to reveal it.

Amazon
Amazon
Customer consensus

The pattern in Amazon reviews is predictable: easy install, subtle but welcome noise reduction, and a few disappointed buyers who expected a much bigger jump.

Reddit
Reddit
Community take

Reddit is more skeptical, and that's healthy here.

Overview

Pro-Ject Power Box S3 Phono Filter Overview

Compatibility, specs, and who this is for

Here’s the short version:

Compatible Pro-Ject phono preamps Output requirement Best for
Phono Box S3 Match Pro-Ject's specified DC requirement Owners who already like the stage and want a finishing upgrade
Phono Box DS3 B Match Pro-Ject's specified DC requirement More revealing systems, especially low-noise passive setups

MM and MC support comes through the phono preamp, not the supply itself. This unit just feeds cleaner, regulated power to the stage.

If your current phono preamp is the weak link, a better stage will usually beat a power-supply upgrade. If your current stage is already good, this is the polish move.

What changed in practice, stock adapter vs filtered supply

Here’s the realistic before-and-after view:

Trait Stock adapter Power Box S3 Phono Filter
Hum Usually unchanged unless supply-related Can help only if the adapter was part of the problem
Hiss / low-level hash Slight background haze possible Often a little cleaner on revealing systems
Bass control Mostly similar Sometimes a touch tidier, rarely dramatic
Image stability Fine in casual listening Can feel slightly more settled at low volume
Low-volume listening Good Often where the upgrade is easiest to notice

In a quiet room, the difference can show up as less grain between instruments. In a louder room, or through entry-level speakers, that same change can vanish.

Troubleshooting before you blame the power supply

Before you buy, check the basics:

  • Confirm the turntable ground wire is attached correctly.
  • Separate RCA cables from power bricks and AC cords.
  • Check whether the outlet is shared with noisy gear.
  • Move wall adapters away from signal cables.
  • Listen for speaker hiss with the phono stage disconnected.
  • Recheck gain settings if you're using a high-output stage.

I've seen this more than once: someone hears buzz on the phono input, then finds the RCA leads bundled with power cords behind the rack. Re-routing the cables fixes more noise than any accessory would.

Once you've ruled out setup faults, the decision gets much easier.

Worth it if Skip it if
You already like your Pro-Ject phono stage and want a blacker background You're chasing a loud buzz or hum first
You listen at low volume in a quiet room Your room or speakers already mask small noise changes
Your setup is compatible and well-grounded You haven't fixed cable routing, grounding, or gain issues
You want cleaner DC power, not a new sound signature You want a dramatic upgrade per dollar

The full review

How the Pro-Ject Power Box S3 Phono Filter performs, point by point

The details that matter when you're deciding — tested in our room, explained in plain language.

01

Sound Quality

When it comes to sound quality, the Pro-Ject Power Box S3 Phono Filter makes its presence known in a subtle yet effective way. The most noticeable improvement for me was during those low-volume listening sessions, where the background noise can become a real distraction. With this filter in place, the music feels cleaner, allowing the nuances of my favorite tracks to shine through without the usual hiss or low-level hash that can plague lesser setups.

In more revealing systems, especially those running MC gain, the benefits become even more apparent. A high-gain setup can expose the tiniest flaws, and the Power Box S3 helps to mitigate that supply-related noise, giving you a more stable and enjoyable listening experience. It’s like giving your system a fresh breath of air—everything just feels a bit more alive.

02

Build & Design

The build quality of the Power Box S3 is solid, as you’d expect from Pro-Ject. It has a compact design that doesn’t take up much space, which is a bonus for anyone with a cluttered audio rack. The case feels sturdy, and it’s clear that they’ve put thought into keeping interference at bay, which is essential for a power supply.

While it’s not flashy, the design is functional, and it fits nicely alongside my other gear. I appreciate that it doesn’t scream for attention; it’s more of a silent partner in the background, doing its job without drawing focus away from the music.

03

Setup & Ease of Use

Setting up the Power Box S3 Phono Filter is a breeze. I unplugged the stock supply, connected this one, and within a minute or two, I was ready to rock. There’s something to be said for gear that doesn’t require a PhD to install—just plug and play, and you’re good to go.

This ease of use is particularly appealing for those who might be hesitant about making changes to their setup. You don’t need to be an audio expert to appreciate the benefits of a cleaner power supply, and this unit makes the transition seamless.

04

Everyday Use

In my daily listening routine, the Power Box S3 has proven to be a worthwhile addition. It shines in quiet environments, like my apartment, where the subtle improvements in noise floor can be truly appreciated. I often find myself reaching for records I haven’t played in a while, simply because the clarity makes them feel fresh again.

05

Upgrade Path / Who It's For

The Power Box S3 is an excellent refinement for those who already enjoy a compatible Pro-Ject phono stage. If you’ve got a good setup going and want to add a bit of polish, this is where it shines. It’s not going to revolutionize your sound, but it can certainly elevate it, especially if you’re running a decent MM cartridge or a more revealing chain.

Pro-Ject Power Box S3 Phono Filter
Pro-Ject Power Box S3 Phono Filter
4.5
$249.00
Get it from Amazon
I earn a commission if you click this link and make a purchase at no additional cost to you.
09/19/2026 04:54 pm GMT

Why trust this review

How we tested the Pro-Ject Power Box S3 Phono Filter

No spec-sheet guesswork. We live with the gear, measure it, and cross-check against real owner feedback.

9+
Weeks hands-on
6
Score axes
2,400+
Owner reviews read
100%
Reader-funded

Our review process

  1. 1

    Buy it ourselves

    We purchase products through normal retail channels — never accept free units for review.

  2. 2

    Live with it

    Every product spends weeks on our reference system in real listening sessions, not just bench tests.

  3. 3

    Measure & compare

    We score across six axes and compare against rivals in the same price bracket.

  4. 4

    Cross-check owners

    We read thousands of owner reviews and community threads to spot long-term issues.

Marcus Webb

Marcus Webb

Speakers & Receivers Editor

I grew up in Columbia, South Carolina, where my dad fixed TVs for a living. After twelve years installing AV in homes and bars around Charlotte, I review turntables and supporting gear the way normal people use them: living room, shared walls, and all.

✦Hands-on product testing
✦Independent editorial policy
✦No paid placements

Our editors' work has appeared in

forbes wired cnet pc-mag the-guardian techcrunch

Final thoughts

Should you buy the Pro-Ject Power Box S3 Phono Filter?

If your setup is compatible, grounded properly, and already quiet enough to expose small flaws, I'd call this a good finishing upgrade. That's especially true with the Phono Box S3 or Phono Box DS3 B in a mid-range passive speaker system.

If you're chasing obvious hum, don't start here. Fix grounding, tracking force, cartridge alignment, and cable routing first.

Compared with the stock adapter, this can bring a lower-noise presentation. Compared with upgrading the phono preamp itself, it's usually the smaller jump per dollar.

✓ Buy it if

  • <h3>Where the Power Box S3 Phono Filter helps most</h3>
  • <p>The main benefit is lower supply-related noise on compatible gear. That matters more on a good phono stage than on a cheap all-in-one system.</p>
  • <p>I hear the case for it most during low-volume listening. A quiet apartment setup with an MM cartridge and passive speakers is where this kind of upgrade earns its keep.</p>
  • <p>Install is easy. Unplug the stock supply, connect this one, and you're done in a minute or two.</p>
  • <p>If you're running MC gain or a more revealing chain, the argument gets stronger. Higher gain exposes small problems fast.</p>
★ Editor's Choice
Pro-Ject Power Box S3 Phono Filter
Scored 4.5/5 · tested hands-on
$249.00 Get the Pro-Ject Power Box S3 Phono Filter →
Pro-Ject Power Box S3 Phono Filter
Pro-Ject Power Box S3 Phono Filter
4.5
$249.00
Pro-Ject Power Box S3 Phono Filter - Elevate your audio experience with clean, stable power for your turntable and preamp.
Pros:
  • Ultra stable power
  • Low noise output
  • Rigid aluminium casing
  • Effective voltage regulation
Cons:
  • Higher price point
  • Requires careful placement
  • Limited to specific setups
Get it from Amazon
I earn a commission if you click this link and make a purchase at no additional cost to you.
09/19/2026 04:54 pm GMT

Still wondering?

Pro-Ject Power Box S3 Phono Filter — your questions

It's an external filtered DC power supply made for compatible Pro-Ject phono preamps. It replaces the stock wall adapter and aims to feed the phono stage cleaner power.

Its main target is background noise. In the right setup, it can lower low-level hash, make quiet passages sound cleaner, and slightly improve image stability.

It can reduce noise tied to the stock power supply, but it won't solve every hum problem. A ground loop, poor cable routing, or gain-related hiss can sound similar but need different fixes.

Sometimes, yes. In a mid-range setup with a compatible Pro-Ject stage, integrated amplifier, and decent passive speakers, I think it can be worth it as a finishing move.

It's easy. For most people, it's a one- or two-minute wall wart replacement.

Usually no. I'd handle setup basics first, then cartridge alignment, tracking force, grounding, and any bigger weak spots in the chain.

The Groove · free weekly

Get our best gear picks before they sell out

Honest reviews, price-drop alerts, and the occasional rare-pressing tip. No spam, unsubscribe anytime.

We respect your inbox. Unsubscribe in one click.