DEMETER VTMP-2B STEREO TUBE MICROPHONE PREAMPLIFIER REVIEW

Audio Media (March 1995)
By Zenon Schoepe

This acclaimed valve preamplifier, with a net DI tucked up its sleeve, was first built in 1987. Now in its third generation, Zenon Schoepe checks it out.

Specifications:

• Input impedance: (mic) 150 Ohms, (instrument) 1 MOhm
• Output impedance: less than 50 Ohms
• Total harmonic distortion at 30dB gain: 0.118 at 20Hz, 0.0662 at 1kHz, 0.0682 at 10kHz.
• Bandwidth at 30dB gain: 0.06dB at 20Hz, -0.34db at 10kHz, -0.78dB at 20kHz, -3.00dB at 65kHz.
• Signal to noise ratio (150 Ohms, 52dB gain): 124.72 EIN

It is an indication of the times we live in that a market for stand-alone mic preamps remains, even blossoms, in the face of desk manufacturers' efforts (and successes) in building ever better front ends. It is perhaps because standards in desk preamps have increased that this kickback exists - raise the general standard and room consistently appears at the top end for something even better. Perhaps this is fuelled by user desire to experiment with something a little different, or simply to bypass the desk altogether in the hope of going to tape more directly. Presented with these criteria, the more esoteric, radical or even retro the preamp, the more appealing it appears.

Demeter's VTMP-2b falls into this category and while not a particularly new unit, it is beginning now to make inroads, outside of its native America. It is effectively the third generation of a design first built in 1987 and has received a pad, low cut, phase reverse, and 10dB extra gain in the last year.

The intention is to combine a core of valve technology with modern components in a package that adheres strongly to the 'valves are best' approach, particularly when working with digital media. Thus it employs Jensen JT-13K6C input transformers, polypropylene capacitors, and metal film resistors. The power supply has full regulation of the B+ voltage and the filament voltage to achieve low noise and quick response.

The valve nature of the unit is outwardly not that obvious. While you can see the glow of the tubes through the top grill (the box employees two 12AX7As, two 12BH7As, and a 12AT7A), to all intents and purposes, it looks like a typically over-engineered bit of substantial and expensive outboard. What you are getting is a dual-channel 2U with a decidedly high-quality feel and enormous rotary faders for fine gain adjustment. Each channel has switched gain settings of 40, 50, and 60dB with a peak LED, a switched 6dB/octave high-pass filter (3dB down at 100Hz), phantom power with LED, 20dB pad, and phase reverse. Interestingly on a unit of this type, but widely in line with Demeter's other activities as regards tube DI boxes, there is also a switch to select mic or instrument level inputs. Instruments enter on a front panel jack, while mic inputs are on the back, along with paralleled XLR and jack outputs.

In Use

For any listening exercise to be meaningful, you really have to stack a box like this up against a comparable quality, non-valve mic preamp. Fortunately I had such a unit to hand from a manufacturer well regarded for its achievements in this particular area in the desk sector. Throw in a selection of microphones, including some large diaphragm mics of Teutonic origin, and the results were interesting and revealing.

Not surprisingly, the non-valve preamp performed admirably, with good definition on a variety of sources. It was also quiet and very dynamic. The Demeter, on the other hand, managed to match all this but had a very apparent warming in the bass region. While it was possible to mimic this effect with a slap of EQ, the sound from the Demeter remained easier to work with. Close up vocals, for example, were more predictable, manageable, and less trouble to optimise. The Demeter also sounded smoother, or rather it made the mic sound smoother, and more extended in frequency response compared with the other box which imparted a slight feeling of treble emphasis.

I'm going to pull back on the tube cliches at this point, because the VTMP-2b sounds markedly fast and clean. It is not characterised by the traditionally soft and muddy front end that can be associated with tube gear. It actually sounds quite contemporary.

You may have noticed that I haven't used the word 'better' when comparing these two preamps and it's deliberate. I believe that at this level in operational terms things can get a tad academic, when it is valid and useful differences that are important. In this respect, the Demeter is certainly different in a way that is likely to appeal to a lot of people.

The word wholesome springs to mind when trying to describe what the Demeter does to a mic signal, because it somehow encapsulates a mic's character more proficiently. It is also immediately flattering to vocal use, providing the right type of mic is used for the singer - you can almost see them puff up a bit with the extra resonance that they discover in their voices.

I realise that I'm focusing heavily on the traditional large diaphragm condenser/tube preamp combination. This is because it is going to be one of the most common uses for the Demeter. Of course, its abilities extend well beyond this into every other mic application, and it is certainly quiet enough for hyper-critical acoustic recording, given low-noise mics and a low-noise venue. Classical music is an obvious choice.

Demeter claim in their promotional literature that the VTMP-2b "makes any ordinary microphone sound like a rare, vintage tube mic", which is rather fanciful. Firstly, it depends what you mean by "ordinary microphone", no my friends, an SM57 does not cut it, although it sounds less like a dynamic and gains a more rounded character. Secondly, it fails to introduce all those inexplicable phuuts and crackles when you need them least that a typical "rare, vintage mic" does. There is no doubt that it can do a good mic justice and the better the mic, the brighter the VTMP-2b shines. If you have grown a little tired of your mic collection, maybe you ought to look at one of these boxes. It is just the sort of purchase that can help you rediscover the mic cupboard.

Instruments

Let's face it, if you were looking at an expensive mic preamp that had an instrument input on it, you would suspect it of being a token gesture to add a little flexibility. In the Demeter's case, you'd be wrong. I half-heartedly plugged in an electric guitar - really to check if the front panel sockets worked. I got badly sidetracked into actually playing for a change. As a DI, it is quite superb but lest we forget, Demeter does big business with its tube direct boxes.

It is the best clean electric guitar DI I have heard - incredibly quiet, rounded and full, with almost eternal natural sustain. Individual guitar character is also retained and it is nothing short of spectacular on electric bass, with a phenomenal capacity to handle low notes without fuss or fizz.

It doesn't take much imagination to start plugging anything on a jack into the instrument sockets, such as synths and samplers. Before long I was hooked.

Conclusion

The VTMP-2b's DIing features add a completely different complexion to the unit as you're getting a lot more than just two excellent channels of mic pre. This will contribute significantly to the amount of use that you'll get out of your investment. It is by no means cheap, but if you acknowledge that you have to be prepared to pay for top-end tube performance, then the Demeter actually starts to look pretty good. As a mic preamp, it is up to any job thrown at it, and it will show the mic off to its very best. It would be the perfect companion for recording voice-overs alongside a digital audio workstation. As an instrument clean DI, I don't believe it has an equal. Consider this to be a real alternative to high-quality non-valve stand-alone preamp designs.