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Edirol UA20

USB Audio + MIDI Interface [Mac / PC] By Martin Walker
Published February 2003

Edirol's latest audio and MIDI interface fills another niche in the increasingly competitive market for USB devices.

Now that initial USB teething troubles have largely died out, there's no denying that USB audio and MIDI peripherals have made a lot of musicians' lives much easier, particularly where laptop recording is concerned. Edirol have been active in this market since its beginning, and the UA20 provides us with yet another tempting combination of features. It supports stereo 24-bit audio recording and playback at a fixed 44.1kHz sample rate, and its inputs can be switched between mic, guitar and line operation.

Edirol UA20 USB Audio+MIDI Interface.Along with line-level outputs, the UA20 also has an Toslink optical digital output, zero-latency monitoring, a separate headphone output, and a MIDI In and Out. Since it's still a little foolhardy to plug in separate USB MIDI and audio peripherals and expect them not to squabble occasionally, this seems a convenient arrangement, especially since the UA20 is parasitically powered from USB, requiring no external wall-wart.


The ABS moulded silver and grey case is smart, and at a diminutive 149mm wide, 111mm deep and 43mm high, should fit almost anywhere. Its rubber feet grip most surfaces well, so despite its light weight it shouldn't slide off the desk if you move your mic or guitar cable. A quick look inside confirmed that like so many soundcards from other manufacturers including Aardvark, Creamware, Marian, M-Audio and Terratec, the UA20 uses AKM's AK4524 converters.

Input controls are ranged across the front, with the two quarter-inch unbalanced jack sockets on the right, a three-way slide switch to select mic, guitar or line level, and a second three-way switch to switch input monitoring between permanent zero-latency monitoring, software-selected monitoring using a suitable ASIO 2.0 host application such as Cubase, or Off. The front panel is completed by a two-way switch labelled Advanced Driver, to choose between the standard 16-bit/44.1kHz USB driver or Edirol's own 24-bit/44.1kHz design, which is claimed to provide more stable timing. All three slide switches are tiny and recessed to prevent accidental operation, but despite being a little fiddly to operate are reasonably positive in action.

Edirol UA20 £159
  • Audio and MIDI support in one convenient package
  • Mic, guitar and line-level input options
  • Low-latency 24-bit audio support
  • Background digital playback interference on the review system
  • Fixed 44.1kHz sample rate
  • Confusing manual
Any musician who wants to plug in a mic or guitar instead of a line-level signal, make 24-bit recordings, and plug in a MIDI synth or two, should find Edirol's UA20 is a compact and convenient solution at an attractive price.


On the top of the unit is a large rotary input level control, along with a funky blue LED to indicate that the USB connection to your computer has been recognised. Two phono sockets provide the main output signal on the rear panel, where there are also a single Toslink optical digital output carrying the same stereo signal, standard five-pin DIN MIDI In and Out sockets, and the USB connector. The controls are completed by a 3.5mm stereo headphone socket and tiny associated level control on the right-hand side of the case (musicians with huge fingers beware).

Driver Installation

You can run the UA20 on Windows 98, 98SE, ME, 2000 or XP, and Edirol provide a helpful list of compatible USB Universal Host Controllers on their web site. Mac users can use Mac OS 8.5, 8.6, 9.x and OS X, and under OS 8 and 9 can use OMS 2.3.3 or later, or FreeMIDI 1.35 or later as the MIDI driver.

Whatever operating system you are using, standard drivers can be installed by making sure the UA20's Advanced Driver switch is set to Off, and then plugging it into a USB port, when it will be detected automatically and any appropriate files installed from the supplied CD-ROM. Since the standard drivers don't provide 24-bit or MIDI support, though, I expect most users will install the special driver, by flipping the Advanced Driver switch to On before plugging the UA20 in. However, Mac users should note that in Advanced Mode they won't be able to play back audio data from Sound Manager.

On the PC, Windows 98/ME users can install their chosen driver at this stage, but Windows 2000 and XP users next have to choose between the WDM or MME drivers. Those who use Sonar (for instance) should select the WDM option, although then they will lose 24-bit support with non-WDM compatible applications. Conversely, choosing the MME driver will give you 24-bit support inside MME applications, but you lose the special WDM features inside Sonar.

Since this is such a new product, the version 1.0 drivers on the bundled CD-ROM were still the most current, so I installed the Advanced drivers under Windows XP, which went without any hitches.

In Use

Sadly, although there's plenty of information in the 81-page manual, it's very scattered. For instance, I'd worked out how to alter the audio latency long before I found the relevant page in the manual, and although this correctly tells you to use the Audio Buffer Size slider in the Driver Settings dialogue box, how to open this box isn't covered until a couple of pages later, with no helpful screenshots, and with four alternative ways to access it depending whether you are using WDM drivers under Windows XP/2000, MME drivers under Windows XP/2000, Windows 98/ME, or a Mac.

Once you've discovered how to launch it, Edirol's Driver Settings utility provides some useful options, although it would help if the current buffer size were displayed in samples or as a latency figure.Once you've discovered how to launch it, Edirol's Driver Settings utility provides some useful options, although it would help if the current buffer size were displayed in samples or as a latency figure.You have to close your audio application before you can change this setting, but having discovered it I was pleased to find that I could run my Pentium III 1GHz PC at the lowest buffer size in Cubase SX 1.03 without any glitching. This gave a latency declared as 144 samples, or 3.3ms at 44.1kHz. Sonar ran very nicely with an Effective Audio Latency of just 2ms, although CPU load was rather high at this setting, while the DirectSound drivers also worked quite well with NI's Pro 52, managing a 25ms Play Ahead setting.

The Driver Settings box also lets you decide whether or not to use the UA20's ASIO 2.0 Direct Monitoring function. Other parameters in the Windows XP WDM dialogue that I was using weren't mentioned in the manual at all. I later discovered that the ±2ms adjustment for Audio Timing is for tweaking the offset of audio recordings in your MIDI + Audio application, while the Light Load tick box for the MIDI In lowers the polling frequency at the expense of a slightly higher MIDI latency.

While the AK4524 converters are capable of 24/96 operation, the UA20's sample rate is fixed at 44.1kHz, to keep costs down. I still use 24-bit/44.1kHz recording almost exclusively, and USB 1.1 can't manage 96kHz in full duplex anyway. I did find it possible to select other rates within various applications, but take care if you do this — any non-44.1kHz sample rate will use software sample-rate conversion, compromising audio quality slightly.

Given that the UA20's converters are very similar to those of my own Echo Mia, I wasn't surprised that the two sounded very similar. RightMark's Audio Analyser showed that the UA20's frequency response was very flat, measuring -1dB down at 5Hz and 20.6kHz, while distortion levels were low at around 0.06 percent. Background noise levels were reasonably good: I measured -92dBA when running at 16-bit/44.1kHz, dropping to -94dBA at 24-bit/44.1kHz. Like the figures I measured for M-Audio's USB Duo, these results are slightly higher than most PCI soundcards, but still perfectly acceptable for the majority of applications, particularly at this budget level.

 Test Spec 
  • Edirol UA20 Windows XP driver version 1.0.
  • Pentium III Coppermine 1GHz PC, Asus TUSL2-C motherboard with Intel 815EP chipset, 512MB PC133 RAM, running Windows XP with SP1.
  • Tested with: Steinberg Cubase SX 1.03 and Wavelab 4.0e, NI Pro 52 2.5, Cakewalk Sonar 2.0.

Recordings made using the line, guitar and mic inputs sounded clean and quiet, but I did experience some quiet but audible background digital interference on my setup during playback that varied when I moved my (non-USB) mouse. I unplugged all other USB devices from my system, tried different USB and audio leads, plus various earthing arrangements, and consulted Edirol Europe and Japan. However, nothing cured the problem on my PC, and I suspect this was also the reason that my noise measurements were slightly higher than the manufacturer's figures.

Thankfully, this interference wasn't present on recordings made using the UA20 when played back via my Mia card, which proved that it was a playback-only issue; nor was it ever audible on either input or output signals while auditioning with the UA20 headphone output. So, it seems that like a few other audio devices I've reviewed in the past, this was down to some grounding anomaly in my particular studio setup, and hopefully it shouldn't happen to you.

Final Thoughts

If you're considering a budget USB audio peripheral, other models to consider include Edirol's own UA3D at the slightly cheaper price of £149; this has the same three input options, but with only 16-bit conversion. If you've got more money to spend, Edirol's UA5 (reviewed SOS March 2002) adds 96kHz support, balanced I/O options, and +48 Volt phantom power for about £249, while M-Audio's USB Duo (SOS October 2002) has similar features at the same price, loses the high-impedance guitar input, but adds the ability to run as a stand-alone A-D converter. However, it's important to point out that USB 1.1 bandwidth limitations mean neither of these can manage full duplex (simultaneous recording and playback) at 96kHz.

Nor does either of these products have MIDI I/O, and plugging in separate USB audio and MIDI peripherals is still asking for trouble, since their drivers could well both end up fighting for their share of USB bandwidth, resulting in audio clicks or MIDI timing problems. M-Audio's Quattro does, again for around £249, along with 24-bit/96kHz support and balanced I/O, but doesn't provide mic inputs. So, unless you've already got a suitable MIDI interface, the UA20 would seem to be a prime candidate for anyone who wants a budget USB-based solution that provides both MIDI and audio support in one convenient package.

infop.gif £159 including VAT.
infot.gif Edirol Europe +44 (0)20 8748 5949.

Edirol UA20: Brief Specification

  • Inputs: two unbalanced quarter-inch jack sockets, nominal level -45dBu to -10dBu, with impedance of 22kΩ (mic and line) and 470kΩ (guitar).
  • Line outputs: two unbalanced phono sockets, nominal output level -10dBu, output impedance 1kΩ.
  • A-D converters: 24-bit 64x oversampling (part of AK4524 codec chip).
  • D-A converters: 24-bit 128x oversampling (part of AK4524 codec chip).
  • Residual noise level: -105dBA (line in to line out).
  • Frequency response: 20Hz to 20kHz, +0.5dB/-1dB.
  • Supported bit depths: 16 and 24.
  • Supported sample rates: fixed at 44.1kHz.
  • S/PDIF: Toslink optical out.
  • Power supply: 170mA (parasitically from USB).