Review of the Music Valve Electronics Vacuum Tube Direct Box by Peter Freeman as appeared in the September 1999 issue of Electronic Musician Magazine.
Overall EM Rating (1 through 5): 4.5
An important link in the audio chain of any studio that is often overlooked is the humble direct injection (DI) box. Its job is to make sure that your low-level instruments make their way safely to the balanced, +4 dBU world of your mic preamp, and ultimately to your mixer or DAW. It's surprising how little thought is given to DI devices much of the time, usually to the detriment of the instruments whose signals have to struggle through cheap and nasty circuitry that compromises their sound rather than preserving or enhancing it. Music Valve Electronics has clearly thought about this state of affairs, and judging by the quality of its Vacuum Tube Direct Box ($550) wants to provide a remedy.
Built to Last
The Vacuum Tube Direct Box is a weighty, lavender-colored beast that represents an utterly uncompromising approach to DI design. According to Music Valve's Nathaniel Priest, it is composed of the best components on the market (some of which were custom manufactured to Music Valve's specifications) so that it maintains the highest possible fidelity. These components include a beefy custom-wound toroidal power transformer, a shielded output transformer, metal-film resistors, polypropylene capacitors, and ceramic tube sockets with silver contacts, all of which are expensive and rarely found in devices of this type. Music Valve professes that the Vacuum Tube Direct Box has a frequency response of 20 Hz - 20 kHz (±1 dB) and a noise floor of -100 dB claims that I found to be quite credible after using the box. It should be noted that this is a unity-gain device; that is, it causes no gain or loss to your signal. Particularly notable is that Music Valve made the DI roadworthy. The circuit board and tubes are internally shock-mounted to prevent damage from impact and vibration, major issues while on the road. Also, the simple overall solidity of the unit¹s enclosure inspires confidence that it will easily withstand the abuse of touring. This is clearly not your average box.
Sonically, the results here are impressive: this is the best-sounding DI I've used. I normally route line-level signals through the DI section of a high-end microphone preamp/EQ device, which has always sounded very good to me. Somehow, though, the Music Valve DI box gives you an extra musical edge that's hard to describe. It seems that the Vacuum Tube Direct Box not only gets the instrument signal from point A to point B but also enhances it in a subtle way. I tried it on guitars, basses, and synthesizers and got pleasing results each time (though the box's character was most apparent on the guitars and bass). A/B comparisons with a well-known budget DI were frankly shocking: the sound seemed to suddenly disappear behind a big, woolly blanket, which promptly vanished when I plugged back into the Music Valve box.
Whether you work in an Alesis ADAT/ Mackie based personal studio or in a Studer/Euphonix equipped professional recording facility, the quality of your DI box is important. And there are several boxes out there to choose from. I definitely recommend that you give the Vacuum Tube Direct Box a listen before you buy anything else.