4ms Power Brick 90W (2022–)
It hums, it powers, it dangles from your rack - and whether it stays or gets swapped depends on how fussy your jacks are.
Overview
The 4ms Power Brick 90W isn't glamorous. It's the quiet workhorse behind the scenes. Introduced in June 2022 and sold alongside 4ms's Row Power modules, it's the official AC adapter meant to keep their DC power supplies running. It's not a synth or even a module. It's a brick, the kind you'd plug into a laptop, used here to feed voltage to a modular setup. Like any good power supply, it's designed to be forgotten - until it whines, cuts out, or refuses to stay connected.
Manufactured by 4ms and marketed as a universal adapter, the Brick 90W is built to power multiple Row Power units daisy-chained together. According to Sweetwater, one of these bricks can run about 416HP - roughly four rows of 104HP - of typical Eurorack modules when paired with compatible Row Power modules. Reverb notes it's enough for three to five rows, depending on your power draw. That makes it a mid-tier option for medium-sized systems, especially with 4ms's own power distribution gear. It's not overkill, and it won't cut it for massive rigs.
The design is straightforward: a black, laptop-style universal power supply with an internal switch-mode circuit, accepting 100-240V input so it works globally without a transformer. It ships with an EU power cable when bought from Thomann, so you may need your own for a US outlet. The output is a 5.5mm x 2.1mm barrel plug with positive center polarity. That's standard, but the cable is not user-detachable. If it fails, you replace the whole unit.
Specifications
| Manufacturer | 4ms |
| Maximum output power | 90W |
| Output voltage | 15-20V |
| Output connector | 5.5mm outer diameter / 2.1mm inner diameter barrel plug |
| Polarity | Positive center |
| Input voltage | 100-240V , 50/60Hz |
| Included accessories | Incl. EU power cable (Thomann) |
| Intended use | For 4ms Row Power Eurorack DC Power Supplies |
Key Features
Laptop-Style Universal Design
It looks like a laptop charger because it basically is - a compact, switch-mode brick that handles 100-240V input, so you can take your modular setup overseas. That helps touring performers and international buyers. There are no bulky transformers and no voltage switches. You just plug it in, assuming your outlet adapter fits.
Optimized for 4ms Row Power Systems
This isn't a generic wall wart. It's designed to pair with 4ms's Row Power modules - including the 25, 30, 35, 40, and 45 variants - and powers them via daisy-chained connections. Sweetwater notes that a single Brick 90W can support multiple Row Power units, making it a central piece in a modular power chain. Reverb confirms it's sufficient for setups like three RowPower 30s or two RowPower 40s.
Barrel Plug: The Achilles’ Heel?
Here's where opinions split. The output uses a standard 5.5mm x 2.1mm barrel plug with positive center, but multiple user reports flag reliability issues. Some describe the connection as flaky, with power cutting out if the cable is bumped or jostled. The plug isn't detachable, so you can't swap in a sturdier cable. Some users have opened the unit and found two wires encased in yellow plastic, feeding into the plug. Whether that's cost-cutting or standard practice, it's become a talking point in forums.
The common workaround is to tweak the jack on the Row Power module to tighten the fit, or skip the 4ms brick and use a third-party unit like a Meanwell. That's not a great look for an official accessory.
Quiet… Until It’s Not
Most users report clean, noise-free operation, which is what you want from a power supply feeding sensitive analog circuits. Others describe high-frequency whining, a faint buzz that creeps into quiet patches or gets picked up by high-gain modules. The usual fix is the same: swap the brick. Some have traced noise issues to the 4ms unit and found silence after switching to a Meanwell or similar. This isn't universal - many users report no issues at all - but the inconsistency makes some buyers hesitant.
Collectibility & Value
The 4ms Power Brick 90W isn't a collectible in the traditional sense. It's a utility item, not a vintage synth or rare module. It does have a market, and prices vary by region: roughly $25-$34 USD, €24.40, or £29.00. Three Wave Music lists a price of $25.00, though it's unclear if that's MSRP or a sale price. No original MSRP has been confirmed, and there's no warranty information publicly available.
Its value is convenience and compatibility. If you're running a 4ms Row Power system, the official brick means plug-and-play assurance, at least in theory. Given the reported connection and noise issues, many owners treat it as a starting point. Replacement cost is low, and so is the barrier to upgrading. Used units show up occasionally, often sold as "works fine" with no mention of intermittent dropouts.
There's no official maintenance guidance, no service manual, and no repair notes. If it fails, it's likely end-of-life. No common failure modes are documented beyond the plug connection issue, but the lack of repairability is typical for modern switch-mode bricks.
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