ART USB Dual Pre

This unit is marketed as a preamp with a built-in USB interface, but most of the time I use it as a good quality portable external sound card. The sound is noticeably cleaner than my laptop's built-in sound card, with crisp top and better low end (and the latency seems lower as well). It has a volume knob and a 'mix' knob that sets the balance between the USB output and the preamp signal.

The case is very solid metal, as with most ARTcessories gear it's an 1U high, palm-sized box with rubber feet and jacks/controls at the front/back. The front houses the preamps with their combi jack/XLR sockets and gain controls.

I normally look at the back where the headphone jack and output volume controls are. This side is hugely crowded with the opening for the 9V battery taking up 1/3 of the space. The rest of the back (an area about the size of a match box!) is shared by the USB connector, mix and volume knob, 1/8in headphone socket, 1/4in balanced jack outputs, an illuminated on/off switch (for when using a battery only) and a non-illuminated switch for phantom power. It is moderately inconvenient especially when the master outputs are in use, but the volume/mix knobs are reasonably accessible being on top. Still, kudos to the engineers at ART for cramming all this in this little box.

In: 1/4 in jack (balanced or unbalanced) or XLR
Out: 1/8 in headphone, 1/4 in balanced output
Computer: USB 1.1, 2 in 2 out at 41100Hz (or maybe 48000Hz) 16 bit.

The preamps sound clean (and compared to tube preamps, thin of course). They do not like clipping at all, but at least you will notice it when they clip :) There are two leds for setting the level (signal and clip), in practice this does the job fine.

There is one headphone output that has enough power to drive a 250 ohm headphone, but not quite enough for a 600 ohm one. The impedance for the master outputs is 600 ohm but the signal level appears the same here (line level).

Can be powered from USB, a 9V battery or the included PSU or any other DC PSU between 7.5-12V -- this is really, really nice touch as you'll probably never need to carry its wall wart. It can provide phantom power from the PSU, from the battery or probably even from the USB port itself. Phantom power can only be switched together for both preamps. The spec sheet claims that it's true +48V.

I should mention that I've never felt it get even slightly warm despite containing so much in such a small space.

Audio interface is USB 1.1 41100Hz (or maybe 48000Hz) 16 bit max. No driver included, this will 'just work' with any modern operating system (I use it on Linux, but should work with Windows and Mac without having to install anything).

You can monitor the signal from the preamps, mixed with the computer output at your taste (the ratio can be set with mix knob). The only annoyance is that the preamp output is hard wired to the left and right output. If you only use one preamp, you'll only hear it on one side. It makes it annoying for the performer to monitor herself on headphones.

There is no bundled software (it's not needed).

The unit works just as well as a standalone preamp. No ground lift or polarity reverse switches for the inputs.

You can use the screw that secures the cover for the 9V battery as a grounding post -- not sure if it's a deliberate design feature, but the DTI isolator has the exact same screw (without battery cover) for grounding purposes.

I've used this unit almost every day for the past four months or so. It is very versatile and I lug it with me along with the laptop everywhere I go. As such, I've noticed a few oddities (some of which must be caused by having to cram everything in the little box):

1. The headphone jack is slowly giving up on me. It's cutting out sometimes when I move the cable. I need to pull it apart to see if it can be fixed by resoldering one of its legs or something.

2. The USB socket seems a little shallow, and this makes the plug feel a bit loose (as if it wasn't fully plugged in). It won't come out but it can be moved a little in all directions. I have a feeling that doing so sometimes causes dropouts in the audio.

3. The battery holder is too tight for rechargeable batteries. You have to be careful that you don't get one stuck or it's stuck for good!

4. When plugged into my laptop and the laptop is plugged into AC power and I touch the chassis, there is an annoying digital interference-type noise heard over the outputs. It's not very noticeable but definitely present. Not sure if it's also present on the inputs, if it was, that would be a lot worse.

These are the only quality issues with the box. Still, I think it's really good value, and I would recommend it to others. I would probably get another one if it was lost or stolen as I don't know of anything else that is so portable and versatile at the same time. If I got eg. a Focusrite Saffire, I would probably not carry it around the same way.

What I wish it had:

1. some way to route the preamp signals to both outputs -- either a "mono" button (I wouldn't even mind if it also mono-summed the computer output); or a switch on the right jack that detected if anything was plugged in and sourced the signal from the left preamp if it wasn't.

2. an illuminated switch for phantom power might be good -- if for nothing else then because I first thought that my unit was faulty because there was no light when I switched it on :)

3. Phase invert on the preamps could be useful but I can live without that.