Putting some tube warmth back into signals is all the rage these days, but Aphex's new microphone preamp doesn't stop there. Roger Brown plugs in his voice sticks and experiences a Tubessence tumescence...

It's fast forward into the past, these days. As digital technology develops at an ever increasing pace, so a parallel movement has sprung up, with old technology re-emerging alongside the new.

Having taken advantage of the advances in digital control and stability, analogue synths and amplifiers are back in a big way. Aphex have a well established reputation for high quality audio exciters, with their Aural Exciter (featuring 'Big Bottom') having transformed many a dance track from a mediocre rhythm workout to a stomping bass-driven groove. Now they're getting in on the retro techno movement, with a tube preamp aimed squarely at that most retro of musical instruments, the human voice.

The Aphex Model 107 Dual Channel Thermionic Microphone Preamplifier, or Tubessence as they more playfully call it, is a 1U-high, grey, rack-mountable preamplifier which combines a solid state input section with a vacuum tube stage, to deliver the 'real' character associated with vacuum tube signal processing.

At the same time, it retains the fast attack transients and low distortion for which solid state circuits are fabled. Employing the tube circuit's low voltage drive level is claimed to extend the life of the tube to infinity. A pretty proud boast, and the time allotted to this review prevents me from fully examining that claim, but the Tubessence's startup routine checks all circuits, and certainly doesn't appear to activate the tube circuit until it has ascertained the power supply is stable.

Only time will tell us whether Aphex have their chips in order, on that score. As most peoples' trepidation about buying a tube preamp stems from concern about tube life, and Aphex are marketing this unit on the strength of that claim, we can only assume they know what they're saying.

First impressions

They certainly know what they're doing when it comes to designing circuitry like this, and I have to report the sound emanating from the Tubessence certainly seemed louder than simply patching my mic in from the desk, and providing phantom power from there. For this test I had the use of Audio Technica's radio-controlled headset mic, and THE MIX's favourite, the AKG C3000. The Audio Technica didn't require phantom powering of course, and proved not to be an ideal candidate for preamplification, with previously inaudible levels of RF signal becoming hissingly audible.

But a little adjustment of the squelch knob on the Audio Technica's receiver unit lowered those to a usable level, and consequently this is the mic I chose to record this month's sequencing tutorial. If you compare that to last month's vocals, recorded without the luxury of the Tubessence, I think you will agree there is a marked 'realness' or presence to be heard.

As I said at the beginning of this paragraph, the levels seemed louder, but on checking the metering at the desk and the recording stage, no appreciable difference materialised. I can only put down the perception of extra 'loudness' to the increased 'naturalness' the tube circuitry had added to my voice.

In use

The Tubessence is simplicity itself in operation, its input points and controls all readily accessible from the front, with only the two outputs and two footswitch mute insert points to be found at the rear, all on 1/4" jacks. At the front, the two channels are both provided with an XLR input, and then switches for a 20dB Pad for cutting levels on very high input mics, an 80Hz bass cutoff to reduce low frequency rumble from wind, bad mic handling or vocal articulation, a polarity switch for tracking down polarity differences in microphones and cables, and a 48v phantom power switch for condenser microphones.

There is also a rubber gain control knob for each channel, as well as LEDs to indicate the state of the aforementioned switches, plus one for signal and overload. Of these latter two, the green OK LED will light up at -20dBu, while the red clip light will illuminate at approximately 6dB before actual clipping, allowing you a little headroom. Simply plug in your mic, allow about fifteen minutes for the tubes to warm up, activate the phantom powering if required and the 80Hz low cut, adjust until the green light is the most active, and there you have it! A perfectly warm, solid, stable mic signal to run into your mix.

There is one other LED on the front of the Tubessence, this one to indicate whether the rear-mounted footswitch mute has been activated or not. Simply plug a normal footswitch into the 1/4" jack, and you have ready control over the muting on that channel. This does mean two footswitches are necessary to provide this facility on both channels. In use, I found no use for the second as I simply turned the phantom power off on the AKG, to quieten that circuit.

The phantom powering is quiet and very stable, and coupled with the presence-enhancing tube stage, really extracted the best from the AKG. I've used that setup to record the vocals for next month's sequencing tutorial, so you'll be able to make the final comparison then.

Verdict

In the final analysis, all this 'perceived naturalness' may sound like a load of old fanny, and those of you who have grown up without hearing tube amplifiers may be forgiven for wondering what all the fuss is about. Anyone who works with sound, and especially vocals for any length of time, will know exactly what I am on about when I talk of the increased warmth and 'presence' the Tubessence offers to these ears. Most sound engineers spend ages setting up mics and reverb to achieve just such an effect.

The Tubessence doesn't supply this in bucketfuls, as an effects processor does, but rather in quality amounts. You might not notice the difference at first, but take it away and then you will. Add to that the dual nature of the preamp, allowing you to match up mic and/or vocal levels before sculpting them in your mix, and the Tubessence certainly comes out a winner. It won't be an essential piece of kit in everyone's studio, but those who do invest in one will find the satisfaction that only owning quality gear can provide.