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

Mix Magazine (January 1996)
By Larry The O

Field Test - Demeter VTCL-2A Compressor/Limiter

Slip a piece of tube equipment into an audio signal chain and you change the sound. Whether it changes for better or worse is a subject of debate that rages as intensely as the merits of digital vs. analog recording. I've been dedicated to digital recording since the release of Sony's PCM-F1, yet my favorite format is still analog 15 ips tape with Dolby SR. But there are obvious sonic benefits of tube processing.

The two most important places to use tube technology are mic preamps and compressor/limiters. Demeter makes both, and the VTCL-2a 2-channel tube compressor/limiter is a fine example of today's resurgence of tube technology.

Once the VTCL-2a is out of the box, the difference between current tube devices and vintage gear is evident. Connect the VTCL-2a, and it's clear that interfacing is one of its strong suits: balanced XLR, 1/4-inch TRS and TT connectors for each input and output. For each input and output, there is also a switch for changing the XLR polarity between pin 2 and pin 3 hot. This makes it simple to accommodate equipment from manufacturers who, after many years, refuse to adhere to the IEC pin 2 hot standard.

The simplicity of the front panel reflects the simplicity of the circuit design inside. Each channel has Input Gain (with overload LED), Attack, threshold, release and output gain controls, plus a bypass switch. A VU meter for each channel is switchable to show input or output levels, or gain reduction. Demeter has thoughtfully included a switch that changes the meter range from normal to -10 dB to facilitate metering of lower-level signals. Finally, there is the power switch and a stereo link switch for true stereo or dual-mono operation.

It strikes me as peculiar that a number of tube compressor/limiters have no ratio control. Operationally, this results in the settings and interaction of the input gain and threshold controls becoming the critical determinants in defining compression ratio. The VTCL-2a is simple to operate, and the easiest way to set it up was by ear, cross-referenced to gain reduction metering. Fortunately, the unit is easy to use, as the bare-bones manual consists of two pages stapled together.

The VTCL-2a uses an opto-isolator for the gain element in each channel, along with five tubes in the signal paths to get that "tube warmth": a GE 12BH7 and a Sovtek 12AX7 for each channel, plus an RCA 12AT7.

Tube compressors generally have, to my ear, a "squishier" sound than solid-state ones, which I find more capable of "transparency." This makes tube compressors great for some applications and less-suited for others. The Demeter exhibits this property, but to a lesser degree than several British tube compressors I have used.

My first session with the VTCL-2a was Every New Day, a live album for singer/songwriter Caren Armstrong recorded at Strings, a private listening room near the offices of Mix. During the show, Armstrong only needed microphones for her voice and guitar, while her two sidemen, Robert Powell and Joe Craven, worked their way through numerous and sundry instruments: guitar, mandolin, violin, lap steel, pedal steel, bass, violin case, "mouth hat," bongos and assorted percussion. Almost every microphone passed through a tube on the way to the ADATs, either in the microphone, the preamp or the compressor/limiter. This was a unique opportunity to gather a lot of information and do direct comparisons between a number of tube devices (I also tried Demeter's VTMP-2 stereo mic preamp for this recording, and it proved to be an exceptional unit: clean, warm and quiet, even at high gain settings). I found the VTCL-2a to be less colored than the other tube compressors I was using, and it was more capable of subtlety.

During the recording, the VTCL-2a was used in dual-mono mode for Craven's mandolin and violin (which was strung with cello strings and tuned an octave down). Mandolin is one of those instruments that benefits from the squishiness of tube compressors, and, with the VTCL-2a set to a fast attack and a fairly low threshold, it sounded splendid, crisp but not edgy, even but retaining dynamic feeling. I had questions about how well it would perform on the violin, which tends to be extremely sensitive to compression, but, setting the attack slower and the threshold higher than the mandolin channel, the VTCL-2a smoothed out "hot" notes and level variations from Craven's stage movements without destroying the violin's fragile dynamics.

The VTCL-2a also saw heavy use during mixing. There was only one overdub for the album, a bass part on the title tune. Setting the VTCL-2a to a fast attack and a fairly low threshold resulted in a beautiful, full-bodied, round tone with a soft attack. Armstrong and I were both delighted with the smoothness of the sound and how it supported the guitar. Several other instruments were processed through the VTCL-2a during the mixing, with the most notable success being the pedal steel, which, like the violin, gained evenness without sacrificing dynamics.

After the success of the VTCL-2a on Armstrong's album, I ventured to try it in another context. I needed to transfer dialog recorded on the set of a video shoot for LucasArts' upcoming game, Rebel Assault 2TM, for which I provided sound design and supervising dialog. Production dialog is notoriously difficult to handle, with level variations being a prime component. Unfortunately, the VTCL-2a's squishiness did not work out so well in this situation. Even on very mild compression settings, the dialog ended up sounding too compressed. A wailing vocalist in a pop recording would have sounded killer with the same setup, however.

Tube compressors have their strengths and weaknesses, and the VTCL-2a is no exception. It took me awhile to get a feel for the controls and develop the touch for setting it to obtain a desired result, but after that it came very easily, and I could quickly hear what it would work for and what it wouldn't. For musical applications, I have not heard a cleaner, warmer and better-behaved tube compressor than the VTCL-2a. High-quality tube equipment does not come cheap, and you want to be sure before you plunk down the big bucks. In my opinion, there's just no doubt about the VTCL-2a.

Larry The O operates as a performing musician, engineer and producer under the rubric Toys In the Attic. He spends his days as a sound designer at LucasArts Entertainment.