Real mic pres for real recordists.



The ULN-2 - Available now with Early Access 3d!



The Dream is Real

The ULN-2 Expanded is the result of a dream to create a piece of audio gear that provides unbelievable audio quality while at the same time offering a degree of mobility and convenience that until very recently was simply not possible. The successful integration of world-class analog stages, excellent A/D/A conversion, and the amazing digital mixing, routing and FireWire connectivity that has already made the Mobile I/O line famous, places the ULN-2 in a unique position among computer audio interfaces.

The ULN-2 Expanded is a portable, high–quality, modular FireWire–based multi-format audio converter, interface, and processor for professional audio applications. The ULN-2 is equipped with two balanced analog inputs on Neutrik™ combo connectors, two channels of Digital I/O (AES/EBU and S/PDIF), eight channels of ADAT optical I/O with switchable TOSLINK support, two balanced analog outputs (1/4" TRS), two balanced monitor outputs for connecting directly to power amps and self powered monitors, as well as wordclock in/out and 2 IEEE 1394 FireWire connectors that support 400 Mbs operation.


The Best Mic Pres Available

ULN stands for Ultra Low Noise and the Mic Pres in ULN-2 live up to the name. Providing massive gain (up to 72 dB) with an EIN of -130.5 dBu, fantastic detail and an ultra-fast slew rate, the ULN Mic pres are up to the most demanding recording situations you can throw at them.

And of course it has the same FireWire connectivity, amazing A/D/A converters and powerful onboard DSP as its older sibling – the Mobile I/O 2882.

Balanced Analog Sends and Returns

The ULN-2 also features balanced analog inserts for each input. This lets you use ULN-2 as a standalone analog Mic pre/direct box; use the sends as an active splitter to drive a backup recorder, or even patch in analog dynamics processing between the Mic Pre and the integrated 24bit/96kHz A/D converters.

Flexible Powering Options

The 4-pin XLR power port on the ULN-2 allows you to power the unit with a variety of readily available broadcast battery systems. The 4-pin power port is compatible with power sources having the following characteristics: 9-30V DC, Pin 4 Hot, 15 Watts.


 Key Features
  • 2 Mic/Line/Instrument analog inputs on Neutrik Combo connectors
  • Balanced TRS analog sends and returns for analog inputs
  • 2 analog outputs on balanced TRS connectors
  • 24bit/96k converters on all channels
  • Headphone amp with front panel volume knob
  • Balanced stereo master control room monitor output with front panel volume control
  • AES-S/PDIF Digital I/O with selectable SRC
  • 8 channels all new ADAT I/O with switchable TOSLINK support
  • v.5 Configurable mixer for near-zero latency mixing and routing
  • Metric Halo’s unique instantiable +DSP processing
  • 4-pin XLR power port for compatibility with most location battery systems
  • 10 front panel preset system/routing memories for stand-alone operation
  • FireWire Connectivity
  • Compact, light, and bus-powerable
  • Total recall with MIO Console
  • OS X drivers with multi-box support


At Home in Any Situation

ULN-2 is the perfect tool for capturing audio wherever inspiration hits, in the studio or on the road. Well suited to any recording situation, the ULN mic preamps provide allow you to work how you want, and not have your work style dictated by your tools.

Equally suited to all sources, from condenser mics to the lowest-output ribbon mics, you can choose your mic and your placement with no concern about the performance of the preamp.

Coupled with Metric Halo’s exclusive Character processing, the ULN preamps are literally the most flexible and best sounding pres available today. You can transition from a wire-with-gain to a gooey tube pre with one click of the mouse, and every input can have the right character for the material you are recording.

Fully balanced analog inserts on TRS connectors allow outboard analog dynamics processing to be introduced between the mic pres and the A/D converters. Wordclock I/O and 4-pin XLR power port (for use with typical broadcast camera batteries) complete the rear panel connections of this highly portable device.

The ULN-2 Expanded is the only unit in its class with an on-board processing engine that supports fully instantiable processing, allowing you to use Metric Halo’s world-renowned signal processing effects without sacrificing your computer’s processing power or introducing any additional latency in your monitor path. From MIOStrip to HaloVerb, the ULN-2 Expanded comes with all the basic production processing you need. And remember, this one rack space audio interface has the ability to run entirely from the FireWire bus of a laptop computer or from any DC power source (9V-30V), making it truly and completely mobile.

Organically Scalable

A unique feature of the Mobile I/O system is that MIO’s work well individually or as a group. Mix and match 2882 and ULN-2 units to create a system that meets your needs for track count and preamp power. Adding a unit to the system organically increases the DSP power of the system, so that your DSP always scales with your I/O. Break your system up for small gigs when playing out or add the units of your mates to build a huge system when required. By standardizing on Mobile I/O, each member of the band can have ultimate quality while working alone, and the band can have huge track counts when playing together. You can’t lose!

Stand-alone Operation

Flexible signal routing and sophisticated patch and preset management systems are also featured in the ULN-2 Expanded, including a front panel, ten-preset register for standalone operation. ULN-2’s front-panel recall system allows the unit to function equally as well as a stand-alone Mic Pre/Converter system. In standalone mode, the ULN-2 operates with the converters directly routed to and from the AES/SPDIF I/O, ADAT or TOSLINK.

As a standalone converter, the ULN-2 provides a 24bit/96kHz stereo front-end with ultra-low noise mic pres for any recording system. It also functions seamlessly as a digital monitor controller, making it ideal as digital headphone amp and studio monitor controller.


The ULN-2 Expanded supports a variety of applications. For studio recording, it provides a very high quality interface to a DAW, offering sound processing or simple file transfer between workstations. Its exceptional sound quality is the perfect complement to the studio’s existing analog to digital conversion chain. Songwriters and engineers can use the ULN-2 Expanded to record and edit on the road, in the hotel, while traveling, or anywhere that inspiration strikes.

The ULN-2 Expanded is suitable for broadcast applications, too. It offers instant playback of two individual stereo sends for music cues or sound effects. The compact package and portable power features mean that the unit can go anywhere users need to work, and make on-site fixes or edit location recordings without the need to send files back to the studio, saving valuable time before air.

In the live performance arena, in addition to operating as a remote recorder for archiving performances or to play out backing tracks and musical cues, the ULN-2 Expanded can operate as a soft-synth mixer and I/O interface. The ULN-2 Expanded is also a great addition to a live sound engineer’s setup, providing a simple and efficient tool for analysis and system venue tuning with SpectraFoo.

Jensen Mod

Introducing the Jensen Transformer option for ULN-2

Since its release in 2002, the ULN-2 has enjoyed a legendary reputation for its pristine, wire-like gain, and has established itself as one of the best values in the professional audio industry.



The ULN-2 possesses virtually every characteristic that is coveted in a Mic Preamp: exceptionally low noise at all gains, exceptionally high gain, excellent common mode and RFI rejection, incredibly flat frequency response, and ultra-low distortion. It simply increases the level of what you put into it without having to consider the nature of the source: Dynamic Mics, Phantom Powered Mics, Ribbon Mics, Instrument or line level signals are all handled with equal ease and quality.

So why change it?

The ULN-2 is an incredibly good Mic Pre, but sometimes you want something that isn’t quite "so pristine". It is well known that a certain amount of low-order harmonic distortion has a way of adding “depth” and “sheen” to everything — which explains the high regard for classic transformer coupled preamps.

Enter the Jensen Option

With the transformer option installed, the ULN-2 acquires that classic character. A few years ago, we fitted a prototype ULN-2 with a pair Jensen JT16-A's just for fun. We found that there were some very nice benefits to transformer coupling the input stage of the ULN-2. The Transformers impart a more "glossy", "smoothed" sound than the capacitively coupled ULN-2, which simply faithfully passes the source. Sonically, it's kind of like the difference between images shot on film and images shot in HD.

Enjoy complete isolation

A second benefit is that the transformer completely electrically isolates the preamp from the source – raising the common mode rejection above its already excellent performance, and providing a measure of confidence when dealing with the unknowns of location sound.

How to get it

The transformer option requires factory installation; we have to remove the cap coupling from your existing ULN-2 and carefully add the Jensen transformers to the signal path. When you order your upgrade, we will issue an RMA for you to send your unit into the Custom Shop and our technicians will install the option for you. Turn around time is typically 1 week from date of receipt of the unit.

If you simply want to order a new ULN-2 with the transformer option pre-installed at the factory, you can do that as well; this version of the ULN-2 is available directly from Metric Halo via Metric Halo Direct or from your dealer.

The transformer option is also available for the ULN-2+DSP.


ULN-2 Technical Specifications

Mic Inputs
Stepped Gain Range +6 dB – +72 dB (6 dB Steps)
Gain Range with Trim -14dB – +70 dB
Input Impedance 3.3 kΩ
Harmonic Distortion @1kHz
(+9dBu in @ 6 dB Gain)
Intermodulation Distortion
1k component
(19 kHz/20kHz @ +8dBu)
-96 dBu
Equivalent Input Noise (E.I.N.)
20 Hz – 20 kHz Flat @ 72 dB Gain
150Ω Source -130.5 dBu
50Ω Source -132.0 dBu
0Ω Source -134.0 dBu
Frequency Response
18 Hz – > 20 kHz ± 0.1 dB
8 Hz – > 50 kHz ± 1.0 dB
3 Hz – >100 kHz ± 3.0 dB
Crosstalk @1kHz
trim link engaged -107 dB
trim link disengaged -132 dB
Max Gain 72 dB
Preamp Headroom 20 dB above Digital Clip
Phantom Power +48v Regulated, high current, individually
switchable, P48 test compliant, short circuit/
hot-swap protected
Physical Specs
Controls Stepped Gain (12 steps 6dB – 72 dB)
Continuous Attenuator on return
Attenuation link
Mic/Line Select switch
Independent Monitor Volume Controls
Independent Phantom Power Controls
[W x D x H]
13.75” x 8.25” x 1.73”
34.9 cm x 21 cm x 4.4 cm
Weight 4 lbs
1.8 kg
Rating 8 watts @ 9 – 30v DC
Connectors 2.1 mm Coaxial
4 pin XLR Broadcast Battery

Hardware Comparison

Which interface is right for me?

While all Metric Halo interfaces are multi-purpose, each has characteristics that make it shine in one use or another:

  • ULN-8: Our top of the line, archival quality unit. The ULN-8 has the quality and features to handle the most demanding jobs. Perfect for everything from classical recording to the mastering suite, or any user that needs ultimate power and flexibility.
  • LIO-8: All the audio quality of the ULN-8, minus the mic pres and +DSP license. Perfect for the editing suite, recording with your own pres or interfacing your analog console. In true MH style, the mics pres and +DSP license can be added if your needs change.
  • ULN-2: Two channels of boutique quality mic pres in a small package. The ULN-2 is at home in the mastering studio as well as your home studio. Perfect for the discerning recordist who doesn't require high channels counts but demands high quality and appreciates portability.
  • 2882: Eight channels of analog I/O that fits in your backpack. The 2882 is clean without being pristine and packs a lot of power.

Use the following table to see the notable differences between the interfaces.


Feature ULN-8 LIO-8 ULN-2 2882
Converter Technology 2nd Generation 2nd Generation 1st Generation 1st Generation
Preamp Technology 3rd Generation Optional (1) 2nd Generation 1st Generation
Analog Technology 3rd Generation 3rd Generation 2nd Generation 1st Generation
DSP Technology 2nd Generation 2nd Generation 2nd Generation 2nd Generation
44.1k - 48k
88.2k - 96k
176.4k - 192k n/a n/a
Channels of A/D 8 8 2 8
Mic pres 8 0, 4, 8 (1) 2 8
Gain 91.5 dB 91.5 dB (1) 72 dB 42 dB
Jensen Option n/a n/a n/a
Noise floor 117.9 dB 117.9 dB 110 dB 110 dB
Insert points 8 0 (8 sends) 2 n/a
Dedicated DIs 2 2 n/a n/a
Metering 15 Segment Multicolor 15 Segment Multicolor 10 Segment
Fixed Color
10 Segment
Fixed Color
Channels of D/A 8
(plus headphones)
(plus headphones)
4 8
(plus headphones)
Output Control Digitally Controlled Analog Digitally Controlled Analog Analog (Monitor Outs), Digital (Analog Outs) Digital/Analog hybrid
Output Control UI FP + Computer FP + Computer FP Only (Analog)
Computer Only (Digital)
Computer Only
Monitor Controller Analog Domain Analog Domain Digital Domain Digital Domain
AES Digital I/O 8 channels
(single wire)
8 channels
(single wire)
2 channels(2) 2 channels(2)
Optical Digital I/O n/a n/a 8 channels ADAT(3)
or 2 Channels TOSLINK
8 channels ADAT(3)
or 2 Channels TOSLINK
Wordclock I/O
Multipurpose encoders 9 9 n/a n/a
Tact Switches 7 7 2 (snapshot selection) 2 (Mute & Dim)
Gain Control UI FP + Computer FP + Computer FP Only Computer Only
Gain Control Encoder Encoder Switch/Pot Computer
Gain Style Digitally Controlled Analog Digitally Controlled Analog Analog Digitally Controlled Analog
2d Card
Ultra-low Latency Mixer
Basic DSP Plugin Bundle
+DSP license Optional(4) Optional(4) Optional(4)
Number of channels to/from DAW over FireWire 18 (5) 18 (5) 18 18
Number of boxes per FireWire bus

3@ 44.1 - 48 kHz

2@ 88.2 - 196 kHz

3@ 44.1 - 48 kHz

2@ 88.2 - 196 kHz

3@ 44.1 - 48 kHz

2@ 88.2 - 196 kHz

3@ 44.1 - 48 kHz

2@ 88.2 - 196 kHz

Bus powerable? No No (6) (6)
DC powerable?
Power Switch No No
Audio I/O connectors DB-25 DB-25 XLR and TRS XLR and TRS
SMPTE I/O n/a n/a
MIDI I/O (7) (7) n/a n/a
Dimensions 17" x 13" x 1.72"
432 x 330 x 44 mm
17" x 13" x 1.72"
432 x 330 x 44 mm
13.5” x 8.25” x 1.73”
343 x 210 x 44 mm
13.5" × 11" × 1.73"
343 x 279 x 44 mm
Weight 6 lbs
2.7 kg
6 lbs
2.7 kg
4 lbs
1.8 kg
4.5 lbs
2 kg
Suggested retail price $4495 $2995 $1595 $1795


1: 4 or 8 channels of 3rd Generation ULN-R mic pres may be installed as a factory option or at a later time.
2: Switchable between AES and SPDIF. ASRC available on input.
3: ADAT does not support SMUX; operation is limited to 44.1-48 kHz
4: +DSP licence can be added for $699 at any time.
5: Firewire transport limited to 8 channels in each direction @ 176.2-192 kHz sample rate.
6: Interfaces may require a "jumpstart" to boot on some laptops. More information is available here.
7: MIDI I/O is for control surface connection, and not optimized for musical input

2d & MIO Console


The brains behind the sound...


2dLogo_badge MIOConsoleGray

All Metric Halo interfaces are built on the 2d DSP card and MIO Console software.

Click here to find out more about these core technologies.



Audio Samples

Click the "Info" button in the player and follow the link to find out more about the track and artist.

Planet Venus Mission 5.8.10 by Vic Stathopoulos

Native Nightengale Experience by Floris Klankschap


All rights reserved by the original artists

System Requirements

  • Computer:
    • Any Mac that supports Mac OS X
    • At least one FireWire port; one port will support 3 interfaces at 44.1 - 48 kHz, and 2 interfaces at 88.2 - 192 kHz
    • Universal Binary (native support for PPC and Intel)
    • Mac OS X 10.6.8 or newer required
  • Peripheral FireWire Adaptors supported:
    • OHCI compliant PC Card, PCI card, ExpressCard or PCIe card
    • Apple Thunderbolt to FireWire adapter, Apple Thunderbolt display, Sonnet Technology Thunderbolt to Expresscard adapter with FireWire Pro 800 ExpressCard/34
  • Software: All CoreAudio compliant software is compatible with Mobile I/O, including:
    • Cubase
    • Digital Performer
    • GarageBand
    • iTunes
    • Live
    • Logic
    • Nuendo
    • PreMaster CD
    • soundBlade
    • WaveBurner
    • Pro Tools
    • and hundreds more…

What's Included

  • One Mobile I/O ULN-2 unit
  • One IEC Power Cord appropriate for your area
  • One 24-volt 48-watt world-ready external power supply
  • One 30” IEEE 1394 9-pin to 6-pin FireWire Cable
  • One 4.5 meter IEEE 1394 9-pin to 6-pin FireWire Cable
  • Two Rack Ears w/ fasteners
  • Rubber feet
  • MIO Software CD-ROM
  • Warranty/Registration Card