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, but in a Eurorack world where clean, reliable power is everything, it’s supposed to be the quiet workhorse behind the scenes. Introduced in June 2022 and sold alongside 4ms’s Row Power modules, this is the official AC adapter meant to keep their DC power supplies humming. It’s not a standalone synth or even a module — just a brick, the kind you’d plug into a laptop, reborn to feed voltage to your modular setup. And 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 comfortably 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 solid mid-tier option for medium-sized systems, especially if you’re building with 4ms’s own power distribution gear. It’s not overkill, but it’s not cutting it for massive rigs either.
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, which might mean you’ll need your own if you’re plugging into a US outlet. The output is a 5.5mm x 2.1mm barrel plug with positive center polarity — standard enough, but not user-detachable, which means if the cable fails, you’re replacing 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 without frying the power supply. That universality is a quiet win, especially for touring performers or international buyers. No bulky transformers, no voltage switches — just plug and play, assuming your outlet adapter fits.
Optimized for 4ms Row Power Systems
This isn’t a generic wall wart. It’s specifically 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, which covers a lot of real-world configurations.
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 — power cuts out if the cable is bumped or jostled. The plug itself isn’t detachable, so you can’t swap in a sturdier cable. Some users have opened the unit and noted the internal wiring: two wires encased in yellow plastic, feeding into the plug. Whether that’s a sign of cost-cutting or just standard practice, it’s become a talking point in forums.
The common workaround? Tweak the jack on the Row Power module to tighten the fit, or ditch the 4ms brick entirely and go with a third-party unit like a Meanwell. That’s not a great look for an official accessory, but it’s a testament to the modular community’s DIY spirit.
Quiet… Until It’s Not
Most users report clean, noise-free operation — exactly what you want from a power supply feeding sensitive analog circuits. But others describe high-frequency whining, a faint but maddening buzz that creeps into quiet patches or gets picked up by high-gain modules. When that happens, 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. Again, this isn’t universal — many users report no issues at all — but the inconsistency is enough to make 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. But 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 lies in convenience and compatibility. If you’re running a 4ms Row Power system, buying the official brick means plug-and-play assurance — at least in theory. But given the reported issues with connection reliability and occasional noise, many owners treat it as a starting point, not a final solution. Replacement cost is low, but so is the barrier to upgrading. For that reason, used units show up occasionally, often sold as “works fine” with no mention of intermittent dropouts — buyer beware.
Maintenance? There’s no official guidance, no service manual, 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.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.