ContentedLife

I’ve become quite a fan of this sound device since I got it about a year ago.

For its price, the sound quality is excellent. It’s fairly packed with features, has a good range of options for input and output connectivity, plus MIDI. And it works flawlessly, out of the box, with Linux — no special setup or drivers required, ALSA knows what it is and how to deal with it in any mode.

The same is true of Mac OS, but only in the basic mode which restricts you to 16-bit 44.1kHz I/O – a driver is required for Advance mode to get up to 24-bit 96kHz support (either in, or out – we’ll come to this under Limitations). This driver can be downloaded free from the Edirol website, and seems to work fine on my new unibody Macbook Pro with OSX 10.6 Snow Leopard, though I haven’t used it extensively on there yet.

I guess it probably works in Windows too, but I wouldn’t know anything about that 🙂

The sound quality (for what I’ve used it for anyway) is very good. It’s stacked with features, and quite versatile… within certain limits.

First we’ll take a quick look at the features packed into this gadget, which is information you could probably find elsewhere but I include for ease of reference, and after that we’ll get to discussing those limitations in more detail.

Features

Packaged in a far more robust metal casing than you might expect in a sub-£100 device, the UA-25 provides A/D and D/A converters, digital S/PDIF I/O (unfortunately optical, rather than coax, so you may need to budget for some converters and Toslink cables), and 5-pin DIN MIDI I/O.

Analogue audio input is via combo balanced XLR and 1/4″ TRS sockets. The XLR inputs have mic preamps (see limitations below) and switchable phantom power, while one of the TRS jack inputs has switchable high-impedance (Hi-Z) mode for connecting guitars etc. Each input has a separate sensitivity (gain) control.

Analogue output is via pairs of both 1/4″ jack and RCA phono connectors on the back, and a stereo 1/4″ jack headphone socket on the front. A single Output level knob controls both the main output volume and the headphone level. I’d have preferred a separate headphone level control, but fair enough, there really isn’t much room left on the front panel!

Sample rate is switchable between 44.1kHz, 48kHz and 96kHz, 16- or 24-bit (but see below). Other features include headphone socket (but note that there is no separate headphone level knob, the Output Level controls both the level of both the main outputs and the headphones); switchable zero-latency monitoring (this does have a separate level); switchable limiter; and an LED which supposedly warns of clipping, or tells you when the Limiter threshold is exceeded… “supposedly”, because…. well, we’ll come to that…

There is no software mixer in the UA-25 at all. All the level controls, including input sensitivity, output volume, monitor volume and the various switches, are hardware controls on the unit itself. I prefer it that way, because I use the UA-25 in a fairly static configuration to record from my mixer, so I like being able to “set and forget” the input gain controls.

Finally, the UA-25 can be powered either from an included “wall wart” plugin PSU, or from the USB bus. In theory, using the separate PSU should give you better sound quality, but in practice I’ve never detected any problem from using USB power; your results may depend on what else you have drawing power from the bus — I generally don’t have anything else on there at all that has a significant power requirement, so the UA-25 isn’t competing to get power. If you have a busy bus, probably best to use the PSU.

Limitations

The UA-25 two significant limitations that you need to be aware of when deciding whether it will suit your needs.

One is well documented, and common for USB soundcards: it cannot do 24-bit 96kHz duplex (input and output simultaneously) – I think because standard USB is simply not fast enough.

The UA-25 has two modes. When Advance mode is OFF, the bitrate is fixed to 16-bit 44.1kHz and the device is full duplex. When Advance mode is ON, the device is EITHER input OR output, 24-bit, at the sample rate selected on the back (44.1/48/96kHz).

If you switch modes, or sample rates, or input/output direction in Advance mode, you have to reboot the device by unplugging and replugging from USB. The device takes a few seconds to boot up every time you do this. If you are going to do a lot of work at 24×96, that’s likely to get tedious and you ought to be looking at a Firewire device – and obviously it’s no use at all if you need full duplex I/O. I suppose you could buy two UA-25s and leave one dedicated to input and one to output. Personally, 16×44 is perfectly adequate for my requirements most of the time so I tend to leave Advance OFF unless I specifically need 24×96 for something.

In either mode, both digital and analogue outputs are available simultaneously, but input is either/or, switched from the front.

The OSX driver for 24×96 support appears to make the Advance Mode UA-25 available for both input and output simultaneously, but in fact you can only do one or the other, as indicated by the fact that the device will be called either UA-25 96kHz PLAY or UA-25 96kHz REC.

The other limitation is completely undocumented, even in the audio path diagram on top of the unit, and I only discovered it by experience: The XLR inputs are hardwired to the Mic preamps. You cannot use them for line-level inputs. I found this slightly annoying as I wanted to plug the XLR outputs of my mixer into them, but you simply cannot reduce the sensitivity enough, and risk overloading the mic preamps if you feed a line-level signal to them. So I had to invest in XLR-to-balanced-jack cables to feed them into the jack sockets.

If you are using the analogue inputs at line level from a device with balanced outputs (such as a studio mixer or a professional DJ mixer), I recommend getting decent balanced cables. Since you can’t use the XLR inputs for this, you’ll need TRS balanced jacks on the UA-25 end of the cables. If you use unbalanced cables, not only will you be more prone to pick up noise within the cable, but you won’t get the best sound quality out of the device (I don’t know why this should be, but every piece of equipment I’ve ever owned which will support either balanced or unbalanced jack into the same socket, seems to sound muddier, not just noisier, if you use unbalanced.

No Peaking

There’s a single LED on the front panel. When the Limiter is switched off, this lights up red, supposedly to indicate clipping. Unfortunately, it doesn’t indicate anything of the sort. It lights up way below 0dB (I’m not sure exactly how far below, but I’d guess about -20dB). ie this light is not really indicative of anything. I wouldn’t mind if is threshold were set a couple of dB below zero, so that you can guarantee seeing a flash if it’s actually clipping, but it can be lit up constantly and the level is still nowhere near clipping. If you enable the Limiter, the colour of the light changes to green and allegedly indicates that the Limiter is kicking in (ie its threshold, which I’d have thought should be 0dB otherwise what’s the point, has been exceeded). But in Limiter mode the LED lights at exactly the same level, still way below necessary. Whether it’s actually triggering the Limiter at that level is hard to say – it doesn’t appear to adversely affect the sound until the peaks start to creep much closer to a level that would actually clip, but the fact of that LED lighting up destroys my trust that the limiter is only kicking in when it needs to.

For live broadcasting on my radio shows, I need to be peaking fairly close to 0dB, so this makes the limiter useless and I have to ignore the LED.

Now, this situation is not unique to the UA-25: my old Phono Plus also cried wolf with the peak LED. Building in some headroom to a peak indicator kinda makes sense in 24-bit where you have a theoretical 144dB dynamic range, and indeed the norm is to “pretend” that -24dB is zero, to make absolutely sure you never clip… but in 16-bit, with only 96dB total, if you turn the gain down so the peak LED never lights you’re sacrificing an unacceptable amount of dynamic range. Or if you use the Limiter, you might be allowing the sound to be coloured by it despite the fact that there’s no need for it to be triggering at all.

Conclusion

I should point out that I only use a subset of the UA-25’s features. I’ve never plugged a guitar into it. I’ve tried a mic but only as a test. The features I’ve used are the line-level analogue I/O, digital I/O, and MIDI.

The Edirol UA-25 is a good quality, robust and versatile little box which offers excellent sound fidelity and a great range of features for the price. The limitations I describe above are annoying at times — particularly the peak LED — but overall, having owned the UA-25 for a year, for the uses to which I’ve put it, I’m very happy with its performance.