DEMETER VTCL-2B STEREO TUBE OPTICAL COMPRESSOR/LIMITER REVIEW

EQ Magazine (January 1996)
By Craig Anderton

Turn on the VTCL-2 and you enter a time warp - there's an all-tube signal path from the '50s, analog opto-isolators from the '60s, LED indicators from the '70s, and the improved performance we've come to expect in the post-CD era of the '80s and '90s.

If this sounds like the recipe for a golden ear kinda device (with a price to match), you'd be right. At just over $2K, this product is clearly intended for those in more upscale studios who are willing to pay for the sound that only a well-designed tube device can deliver. Is it worth the financial stretch compared to budget devices?

Specs and Basics

The VTCL-2 is a two-rack-space, 2-channel compressor/limiter (C/L) with switch-selectable stereo or dual-mono operation. Each channel has controls for input gain, threshold, attack, release, output gain, and analog VU meter monitoring mode (input, output, or amount of attenuation; an associated switch selects two different meter ranges to accommodate -10 and +4 signals). There are also dual-bypass switches and overload LEDs. There's no ratio control; the ratio is a function of how much compression you're adding, which gives an extreme "soft knee" response. This is at least partly responsible for the VTCL-2's non-intrusive processing.

The tubes used are two 12AX7A, two 12BH7A, and one 12AT7A. They're hit with 250 V of B+ voltage (enough to make the tube's plates snap to attention), and both the B+ and filament voltage are regulated. Speaking of voltage, the VTCL-2 runs on either 117 or 240 volts.

The input impedance is 27k, so guitars and such will need a preamp. Tape tracks, synths, drum machines, and other line-level signal sources work just fine.

Incidentally, Demeter obviously subscribes to the theory that you get better sound if the high-frequency response extends well above the normally accepted range of human heading; response is quoted at -3 dB at 65 kHz.

Facing the Interface

There are three unbalanced connectors for each input and output (12 total): 3-pin XLR, 1/4-inch phone, and TT. An optional upgrade using Jensen transformers can balance the XLR connectors for $150 per input pair or output pair. A Switch chooses pin 2 (IEC standard) or pin 3 hot.

Using It

The manual is one page and has no graphics; it doesn't even come close to explaining how to use a C/L. However, Demeter says a revised version is on the way with presets contributed by users.

Getting back to the unit, I like the sound of tubes and also the way the opto-isolators work in the context of a compressor - the seem to give a more "natural" sound (possibly because of small amounts of distortion inherent in opto-isolators). Demeter has managed to merge the two technologies, along with modern-day construction practices, to give the equivalent of a '50s compressor brought up to the state-of-the-art. If you're careful when setting levels, it can be extremely quiet (EIN is quoted at -110 dB with 40 dB of gain), and the controls cover enough range to be very useful (attack: 0.5 ms-100 ms; decay: 200 ms-10 secs).

Opinions

There are many compressors, each with a characteristic sound quality. In fact, people sometimes choose a particular C/L because of the coloration. I'd say that the VTCL-2 has a somewhat warm, "sedate" sound as opposed to the occasionally brighter timbre of solid-state gear. This coloration is subtle, even with relatively extreme compression settings, and is very "supportive" to an instrument. It sounds more like it's pulling sound out of the signal rather than adding an overlay.

This is not a compressor for everyone - nor is it meant to be. However, one factor that makes the VTCL-2 a bit more cost-effective is that it can also be a tube preamp capable of warming up just about any sound (try this with drum machines, synths, and digital tape track outputs; you'll be delighted). Just hit the bypass of set the threshold for minimal compression (the meter's attenuation range clues you in) and you're set.

On a more subjective level, this is a C/L with a light touch - it's kind to your signal and does not give an obviously "compressed" sound. Part of this may be due to the inherent decay time preset in an opto-isolator; the compression action is very gentle and natural. The downside is that you can't set fast enough release times to give those outrageous "sucking drum" sounds (as used on several Beatles tunes) that compressors often did back in the '60s. I assume, however, that most people would consider that a relatively small tradeoff.

Overall, if you do have $2000 to spend on a compressor - and the rest of your system is clean enough to appreciate the Demeter's sound quality - you'll like what you hear.

Applications: Dynamic range processor/tube "warmer" for voice, tape tracks, musical instruments, and other 2-channel program material.

Summary: This is a natural-sounding, non-intrusive compressor/limiter that will delight well-heeled tube fans.

Strengths: Pure tube sound; good metering options; well-built; multiple input and output connectors.

Weaknesses: Costly compared to nontube compressors; minimalist manual; captive, two-conductor line cord instead of three-conductor type.