Bass Player Magazine (March 1993)
By Tom Mulhern
Type: Rackmount tube preamp
Dimensions: 3" x 10" x 19"
Weight: 9 lbs., 3 oz.
Front panel: High and low 1/4" inputs, volume control, bright switch, treble control, middle control, bass EQ switch (60Hz/120Hz), bass control, presense EQ switch (3kHz/6kHz), presence control, power switch w/ LED
Rear panel: Two 1/4" outputs, 1/4" effects return and send jacks, flat/EQ switch, XLR direct output, ground-lift switch
Other models: VTBP-201L, w/out Jensen transformer; VTBP-202DB, w/ bi-amp crossover
Using a separate preamp and power amp is a great way to get the tone you want and the volume you need, plus the flexibility to upgrade easily. You can also "slim down" for distant gigs; rather than lugging your whole rig, you can walk in with just your bass and preamp and use a rented power amp and speakers.
One of the best, and most straightforward, preamps around is the Demeter Tube Bass Preamp, a 1-1/2-rackspace unit that provides clear, robust sound with a minimum of knob twisting. Despite its Spartan appearance, make no mistake: this preamp is of the bare-knuckles, rather than bare-bones, variety.
Design and construction. There are two circuit boards inside the steel enclosure: one for the power supply and one for the audio circuitry. Both are held firmly on metal standoffs, so there's little chance of damage in transit. The wiring is very clean, and when two or more wires run for more than an inch, they're twisted around each other, providing extra strength and reduced wiggling. The Jensen transformer employed for the direct output is of very high quality, as are all the other components: close-tolerance, high-wattage resistors and reliable polypropylene capacitors populate the audio circuit board, and all the jacks are super-strong Switchcrafts. The power-supply board and the AC transformer are located far from the audio board, reducing the possibility of hum creeping into your signal. Two 12AX7A/ECC83 tubes glow inside the chassis; they're well protected, and the vent holes in the top offer more than adequate ventilation. This all adds up to quietness and reliability.
The effects loop comes right after the tone controls, the optimum location in the circuit. You can tweak your tone and then send it to the effects loop, thus routing the full flavor of your EQed bass through your reverb, chorus, or whatever. I found the loop didn't work as well with stomp-box effects as it did with rack units, which operate at a different level and have input and output gain/volume controls, simplifying level matching.
To connect to a power amp, you can use either or both of the 1/4" outputs. The jacks are wired in parallel, so you can send the output to two different power amps or to two channels of a signal processor. One of my favorite schemes is running parallel outputs to separate channels on a mixer; I use one as a full-range feed while I cut the bottom out of the other. I add effects to this second channel, so I can have flanging, chorusing, or reverb without diluting my primary tone.
Controls and operation. The Demeter has a pretty spare front panel, but its no-nonsense controls get right to the heart of your sound. Some preamps have incredible boost/cut ranges that can be abused easily; the Demeter's tone circuits, however, provide smooth and even control over their entire range. And if the feel of a good pot instills confidence, then the Demeter will make you secure.
I started with all of the knobs at their midpoints and settled in for a knob-twiddling session. My first adjustment was the treble control, since I wanted to add a bit of cutting power for slapping. I quickly discovered how the treble and presence controls (and the bright switch) work together to sculpt high-end response. Even when I wanted an extra-bright tone, I didn't have to turn the treble and presence knobs all the way up. Naturally, an old Gibson EB-3 needs different settings than a new bass with a graphite neck and EMG pickups, but rest assured that this preamp can bring out the shine in active or passive instruments of all vintages.
If you activate the bright switch and raise the treble and presence to their full-up positions, you hear some hiss. Chances are, though, you won't like the tone yo get with this much treble, anyway. Backing the presence down to about its mid-point and adjusting the treble knob, I was able to get as much brightness as I wanted without enduring any brittleness or hiss.
The bass and midrange controls are real standouts for their smooth response. Many midrange circuits add a hellacious nasal quality when they're cranked up, but the Demeter's simply boosts or cuts the midrange frequencies without introducing any "quack." I also enjoyed the scooped-out '70s funk tone I got by backing off the midrange and cranking the bass and treble.
The bass control is well behaved, covering a good range without being ridiculous (I've tried preamps that let you boost the lows by 15dB, creating a rumbling swamp that engulfs everything). The bass EQ switch lets you select the frequency center of the bass control, 60 Hz or 120 Hz, and the knob gives you 9dB of boost or cut. I like having the center set to 120 Hz, even with a 5-string bass; this seems to give the tone more body, and I found it particularly good for slapping (of course, your gear and playing style may guide you differently). The presence EQ switch chooses between 3kHz and 6kHz frequency centers, allowing you to boost as much as 12dB above these points. I'm really on the fence as to which setting I prefer: both are well beyond the fundamental frequency ranges of even a 6-string bass, so the effect manifests itself in overtone colors, finger noise, and cutting ability.
The VTBP-201DBL preamp is also a direct box. That is, it has an XLR output with transformer isolation, ready to plug right into a mixing console. Like any good direct box, it has a ground-lift switch for getting rid of the hum that often comes from having multiple ground connections in one circuit. The flat/eq switch is a great feature: the flat setting lets you send your straight sound (with buffering) to the board while using effects and tone tweaks onstage; the EQ setting takes the signal after it's passed through the tone controls and effects loop and routes it to the XLR jack.
Note: If all you need is a direct box, Demeter offers the VTDB-2 single-channel tube direct box for $449. It uses a single 12AX7A/ECC83 tube to add warmth to your sound and features a unity/boost (10dB) switch, 1/4" input and output jacks, an XLR direct out, a ground-lift switch, and AC power. Its sound is clean, solid, and smooth, just what the doctor ordered.
Comments: The Demeter Tube Bass Preamp is a professional-quality unit that offers what most bassists really need: easy-to-use controls, clean tone, and very fast transient response - plus the warmth and meatiness of tube sound. It's also very quiet and built like a bunker. If you get one of these units, it will probably become the "heart" of your rack system. You may pop signal processors and power amps in and out, but I'd almost bet you'll want to keep the Demeter right where it is.
Tom Mulhern was an editor at Guitar Player for 13 years and is now a freelance writer and consultant. His current projects include editing the forthcoming GPI book Bass Heroes, a collection of 30 interviews that were published in Guitar Player between 1973 and 1989.