Metric Halo mkIV: ULN-8, LIO-8/4p or LIO-8 — which one to choose?

At Metric Halo, the mkIV range comes in three references that, at first glance, look remarkably alike: the same 1U rack chassis, the same USB-C connectivity, the same converters, the same DSP. And for good reason — it's the exact same platform. The only real difference between them is the number of mic preamps installed: 8, 4 or 0. This guide compares the ULN-8 mkIV, the LIO-8/4p mkIV and the LIO-8 mkIV to help you choose the right configuration without paying for what you don't need.

Three interfaces, one single platform

Metric Halo designs its interfaces as true studio consoles in an ultra-compact rack format, built to last. All three mkIV models are based on the same 3d Core digital engine and share the same chassis: they are, physically, the same converters, the same mixer and the same monitor controller. What sets them apart comes down solely to their mic preamp section, which is installed in blocks of 4 channels. In other words, when you're torn between the three, you're not comparing conversion, DSP or monitoring features — all of that is identical. You simply choose how many preamps you want to start with… knowing you can add more later.

What the three models have in common

Here's everything the ULN-8, the LIO-8/4p and the LIO-8 mkIV share identically:

• mkIV (4th generation) A/D and D/A converters, from 44.1 to 192 kHz, DC-coupled for minimal phase distortion
• 3d Core engine with MH-Link and +DSP license: over 100 plug-ins running directly on the hardware, at zero latency (ChannelStrip, Sontec MES-432, Character…)
• Multi-source analog monitor controller with Dolby Atmos support up to 7.1.4, plus a relay mute that protects speakers and headphones from clicks/pops
• Internal 128-channel x 64-bus mixer and an integrated tracking DAW (Session)
• Dedicated headphone amp with its own conversion, and 2 high-impedance DI inputs (Hi-Z)
• EdgeBus slot for EdgeCard cards (ADAT, MADI, AES, SPDIF…) and MH-Link chaining
• 19" 1U rack chassis (2.7 kg), USB-C connection, fanless operation

So the choice comes down to a single question: how many mic preamp channels do you need?

ULN-8 mkIV — the loaded version, 8 preamps

The ULN-8 mkIV is the fully-equipped model, shipping with eight ULN-R mic preamps. These boutique preamps deliver up to 90 dB of analog gain in 0.5 dB steps, switchable +48V phantom power per channel, and Metric Halo's Character processing to color the sound at will. On the connectivity side: 8 mic inputs, 8 line inputs and 8 line outputs, 8 sends/inserts on Sub-D25, plus 2 Hi-Z inputs on the front panel.

Who is it for? Those who record several mic sources at once — drums, a full band, live sessions — and want a fully self-contained tracking station without relying on external preamps. The "I want it all, right now" choice.

LIO-8/4p mkIV — the balance, 4 preamps

The LIO-8/4p mkIV is the exact same machine, shipping with four ULN-R preamps and room to add four more whenever you like (5-8 expansion kit). You start with 4 quality mic channels and move up to 8 later, without changing interface. Everything else — conversion, DSP, Atmos monitoring — is identical to the ULN-8.

Who is it for? Hybrid studios that already own a few external preamps but want 4 excellent mic channels on hand, with the door open to 8. Arguably the best versatility-to-price ratio in the range.

LIO-8 mkIV — the pure converter (upgradeable), 0 preamps

The LIO-8 mkIV is the version with no mic preamps at all: a pure conversion and line-connectivity interface (8 line inputs and 8 line outputs + 8 sends/inserts on Sub-D25). You get all of Metric Halo's conversion and DSP without paying for preamps. And if your needs change, it accepts the exact same ULN-R preamp kits, in blocks of 4 channels (up to 8) — so it's never a dead end.

Who is it for? Mastering engineers, monitoring setups and anyone who already owns their own preamp chain and above all wants the best possible conversion. It's also the entry point in the range's pricing.

Comparison table

	ULN-8 mkIV	LIO-8/4p mkIV	LIO-8 mkIV
Mic preamps	8 (ULN-R)	4 ULN-R (expandable to 8)	0 (expandable to 4 or 8)
Line in / out	8 / 8 (Sub-D25)	8 / 8 (Sub-D25)	8 / 8 (Sub-D25)
Hi-Z DI inputs	2	2	2
mkIV conversion	44.1–192 kHz	44.1–192 kHz	44.1–192 kHz
3d Core DSP + 100+ plug-ins	Yes	Yes	Yes
Atmos monitoring 7.1.4	Yes	Yes	Yes
Typical use	Multi-source tracking	Scalable hybrid studio	Mastering / monitoring / line
Price	€2,959	€2,555	€2,333

So, which one should you choose?

• You record a lot of mic sources at once → ULN-8 mkIV; its 8 preamps make you self-sufficient.
• You have a hybrid studio and want a scalable base → LIO-8/4p mkIV; 4 preamps today, 8 tomorrow.
• You already have your preamps and are after the best conversion / monitoring → LIO-8 mkIV; all the Metric Halo without the extras (and upgradeable if needed).

Growing your interface

Whichever model you pick, nothing is set in stone. You can add ULN-R preamps in blocks of 4 channels, install an EdgeCard to expand digital connectivity (ADAT, MADI, AES, SPDIF), and chain several units over MH-Link to multiply the channel count — DSP power grows automatically with each unit added. That's the whole point of the 3d platform: your system always scales to your needs.

Availability and pricing

All three Metric Halo mkIV interfaces are available at Cool Kids Audio:

• Metric Halo ULN-8 mkIV — €2,959
• Metric Halo LIO-8/4p mkIV — €2,555
• Metric Halo LIO-8 mkIV — €2,333

Got a question about the right setup for your studio? Get in touch and we'll help you choose.