This full-featured box makes some of the best sounds on earth.

By Peter Freeman

Over the last decade, Avalon Design has gained a reputation for making top-of-the-line recording and mastering gear. But for most Avalon equipment, the superb quality is matched by prices that are beyond the reach of mere mortals. Recently, however, company founder and CEO Wynton Morro developed a product that occupies a more affordable range of the price spectrum yet maintains the same quality and attention to detail found in the rest of the Avalon line.

The VT-737 is a single-channel, vacuum-tube, class-A device that combines a tube mic preamp, DI, compressor, and parametric equalizer in a 2U rack-mount package - all for $2,195. By most personal-studio standards, of course, that's still a colossal chunk of change; but relative to the prices of Avalon's other offerings - $1,800 for a mono mic pre, $4,200 for a dual-mono compressor, and $5,200 for a dual-mono parametric EQ - it's an attractive deal.


The unit's rear panel provides three balanced XLR connectors, one each for mic input, line input, and line output. There is also a 1/4-inch stereo-link jack that allows two VT-737s to function in stereo mode. The unit is powered internally and offers a removable IEC power cord.

In keeping with the VT-737's myriad functions, its hefty front panel - a 1/4-inch-thick slab of machined and brushed aluminum - is densely populated by knobs and push-button switches. We're not just talking ordinary knobs, either: these are molded in a distinctive cross shape and colored bright purple to match the front panel's purple silkscreened lettering. The switches are distinctive, too, with each one clear red and backed by a yellow LED that glows brightly when the button is engaged.

A 1/4-inch, unbalanced, high-impedance DI jack is thoughtfully provided on the lower left side of the front panel, a very convenient feature for direct inputting of guitars, basses, and other instrument-level signals. This feature, however, is but a small indication of the VT-737's versatility.

The Avalon VT-737 combines a tube mic preamp, Dl, optocompressor, and 4-band parametric EQ into a gorgeous 2U rack-mount box. The unit is superlative in every regard.

Also occupying the left side of the front panel is the preamp section, which offers knobs for gain; selection of instrument, line, or mic input; and a switchable, variable highpass filter with settings at 30, 32, 35, 40, 50, 60, 70, 80, 100, 120, and 140 Hz. (How's that for exacting?) Adjacent to the preamp control knobs is a column of four Input Mode switches labeled High Gain (adds a boost to overall gain), Phase (reverses polarity), +48V (phantom power on/ off), and Hi Pass (filter in/out).

Next up is the compressor section, which provides knobs for Threshold (-30 to +20 dB), Compression (1:1 to 20:1), Attack, and Release (each labeled simply F and S for fast and slow). Three switches complete the compressor section. The first, labeled EQ>Com, inserts the EQ before the compressor. (Normally it's postcompressor.) A second switch, labeled Meter, switches the analog VU meter to monitor gain reduction rather than VUs. The third switch, labeled Compress, switches the compressor section in or out.

In the center of the unit, framed by an oval window beveled into a fat block of machined aluminum, is a large, backlit, very elegant-looking analog VU meter. Below that, centered on the same aluminum block beneath the words "Avalon Vacuum Tube," sits the unit's power-on indicator, a bright red LED. The block of aluminum, bolted to the reassuringly chunky front panel, not only looks good but adds to the VT-737's aura of mass and solidity. (Incidentally, I took the review unit on tour in Europe, and it was the only device in my rack that didn't suffer a bent front panel from the stresses of shipping. Clearly, the beefy build isn't just for show.)


The VT-737's EQ section, which takes up most of the space to the right of the VU meter, is thoroughly implemented and very impressive both in terms of design and sound. It offers 4-band parametric-style equalization via eight knobs and four switches. The top four knobs, labeled Bass, Low Mid, High Mid, and Treble, provide cut/boost while the lower four offer variable, fixed frequencies for each band. The bass and treble bands are passive, a design choice that, according to Morro, results in smoother, more natural-sounding equalization. This is not to say that the low-mid and high-mid bands sound harsh or "electronic" as compared to the bass and treble bands, but they do possess a different character.

The EQ section is remarkable for a number of reasons. First of all, the frequencies chosen for the four bands cover an extremely wide range of the spectrum, more than just about any other device I've seen. For example, the bass-frequency control, a 4-way selector knob, offers four settings: 15, 30, 60, and 150 Hz. Moreover, up to 24 dB of cut or boost is available for the bass frequencies, which is very unusual indeed; typically, equalizers offer about 12 to 15 dB.

Four frequencies are offered on the treble end, as well: 10, 15, 20, and 32 kHz, with up to 20 dB of cut/boost available. Although some might argue that 32 kHz is above the range of human hearing and thus is impractical or unnecessary, I found the band quite useful. On source sounds that contained substantial high-frequency content - cymbals, for example - the 32 kHz added "air" to the signal in a very musical way. Of course, this frequency range isn't that practical for most sounds, but it does constitute an important and thoughtful inclusion. The low-mid and high-mid bands allow for 16 dB of cut or boost each. The low-mid band offers settings of 35, 40, 50, 75, 100, 200, 250, 300, 350, and 450 Hz. However, these frequencies can be "ranged" to a power of ten by engaging the FREQ (x10) switch located between the knobs. Ranging the low-mid frequencies, for example, bumps them up to 350 Hz, 400 Hz, 500 Hz, and so on. This frequency-multiplying system is implemented on the high-mid band as well, which offers initial settings of 220, 250, 350, and 550 Hz, and 1, 1.4, 1.6, 2, 2.5, and 2.8 kHz. (The 2.8 kHz setting, when ranged times ten, becomes 28 kHz!)

VT-737 General Specifications
Audio Inputs (1) balanced XLR, mic-level; (1) unbalanced %", line-level (front panel)
Audio Outputs(1) balanced XLR
Frequency Response10 Hz—120 kHz (~ 0.5 dB)
Distortion THD, IMD0.5%
Output Gain-45 dB to +10dB
Noise-92 dB (20 kHz unweighted)
Equivalent Input Noise, Mic-116 dB (22 Hz—22 kHz unweighted)
Dimensions2U x 12" (D)
Weight 22 lbs.,/p.


Bandwidths for the low-mid and high- mid bands can also be varied by en- gaging the switch labeled HI-Q. With the HI-Q switch in the out position, bandwidth is approximately 3.5 octaves; the in position narrows it to 2 octaves.

Rounding out the EQ section are two other switches, one for EQ in/out, and another, labeled SC<EQ, that switches the two Mid bands from the audible EQ circuit to the detector of the unit's compressor section, allowing for de-essing and other frequency-dependent compressor applications. This is an unexpected bonus, adding even more power and flexibility to the VT-757. As you might imagine, the VT-737's EQ provides extensive control and rep- resents one of the most comprehensive designs around. In fact, in this price range, this much control is all but unheard of.


used the VT-757 on a variety of instruments, from trumpet to voice to electric bass, both in a studio context as a front end for Digidesign Pro Tools and live as part of my bass rig. With the voice and trumpet, I mainly relied on the unit as a mic preamp, using the compression and EQ only sparingly. On bass, however, I employed the compressor and EQ sections extensively, creating a range of sounds from straightforward to "hyped."

The first thing I noticed about the VT-737's sound is its immediacy and integrity. There's a wonderful directness to the sound, allowing all the subtleties of the source to be heard. Every signal I put through the unit exhibited a startling degree of clarity, as if a cover had been lifted off the sound. This is no doubt a result of the pure, Class A circuitry and highest-quality components; the benefits of Avalon's uncompromising design philosophy are clearly audible in the VT-737.

On trumpet and voice, the VT-737 did an amazing job of presenting their respective sounds both accurately and beautifully, with no noticeable coloration. In fact, the mic preamp sounded so good that practically no EQ was necessary, though I did get good results when adding a very small amount (less than 0.5 dB) of 16 or 20 kHz for a little extra "air."

Also apparent was the extremely high headroom of the mic pre's input stage. A trumpet produces large amounts of concentrated midrange energy. All the other mic preamps I've tried on trumpet (including one quite expensive, high-end unit) have produced some distortion. But with the VT-737, I was able to get a pure, clean, undistorted tone with just a bit of careful tweaking of the preamp gain control.


I had the most fun with the VT-737 on my main instrument, the bass guitar. The unit provides a pristine bass sound, and I appreciated the convenience of having the DI jack on the front panel. But it wasn't until I began working with the compressor and EQ sections that things really came to life.

The VT-737's compressor is very, very smooth and sounds quite natural and musical no matter how you set it. Even with high ratios and a low threshold, I still got pleasing results, despite the degree of "squashing" that was taking place. This musicality allows the compressor to be

used in a wider range of applications than is possible with a lesser device; it flatters rather than flattens the sound.
VT-737 Processing Specifications

Preamp Gain

40 dB

High-Gain Boost

20 dB mic and instrument; 10 dB line

Phase Reverse

available on all three inputs

Phantom Power


Highpass Filter

30—140 Hz, 6 dB/oct.



-30 dB to +20 dB



Attack Time

2-200 ms

Release Time

100 ms—5 sec.

Makeup Gain



Bass Band

15-150 Hz, ~24 dB (stepped, passive)

Low-Mid Band

35—450 Hz, 300 Hz-4.5 kHz, ±16 dB (stepped, active, ranged), high/low Q

High-Mid Band

220 Hz-2.8 kHz, 2.2—28 kHz, ±16 dB (stepped, active, ranged), high/low Q

Treble Band

10—32 kHz, ±20 dB (stepped, passive)

In the EQ department, the VT-737 is extremely impressive. Equalization is one area where inexpensive equipment usually falls down hard because it's pretty much impossible to create a gentle, musical-sounding EQ circuit cheaply. The best way I can describe the behavior of the VT-737's EQ is to say that it makes instruments sound as if they already possessed the equalization you've chosen. In other words, there's no sense of the EQ being "imposed" on top of the original signal. The EQ is so natural sounding that even with large amounts of cut or boost, a musical quality remains, devoid of any harshness or ugliness. Again, this is something that normally costs big money.

I found the EQ's design to be extremely flexible, particularly with the two mid controls and x10 frequency multipliers. The tonal coverage goes well beyond that of any other EQ I know of in this price range. And being able to send the mid bands into the compressor sidechain only extends the unit's value.

In general, no matter what applications I threw at the VT-737, it sounded amazing. I have absolutely no reservations about its sonics. This is a totally stellar-sounding box.


Avalon offers the VT-737 in another version, the VT-737sp, which is different in two respects. First, it replaces the standard purple plastic knobs with the solid, machined-aluminum variety found on the rest of the Avalon product line. Secondly, it employs a larger input transformer in the mic preamp section, which according to Morro yields greater low-end handling capability before saturation.


The Avalon VT-737 bears witness to an obsession with quality at every turn. For example, instead of normal potentiometers for the front-panel knobs, Avalon chose expensive, conductive-plastic pots for their superior performance. Furthermore, there are 22 sealed silver relays inside this box, along with ceramic tube sockets, and military-spec Russian tubes - not to mention a 150W toroidal power transformer and discrete, Class A power-supply regulators. There's even an internal tube-life LCD indicator to let you know when the tubes need replacing. Indeed, the VT-737 is so impressive in every way that it's difficult to avoid the feeling that, even at $2,195, one is getting away with something.

I have no complaints about the VT-737. How could I? It looks great, sounds fantastic, is built like a tank, and costs less than I would expect for such a premium device. When was the last time that happened? My only suggestion (the word "complaint" is inappropriate here) is that a secondary output-level control - postcompressor - be provided for applying makeup gain. That would be useful, but it's not essential. The Avalon VT-737 is a top-notch, world-class device that will greatly enhance just about any instrument or recording path. We're not talking "personal-studio quality" here, people - this is the real deal. If you need any of the things the VT-737 does, just buy one and ask questions later. You won't have any, I'm willing to bet.

Peter Freeman is a freelance bassist, synthesist, and composer living in New York City. He has worked with such artists as John Cale, Jon Hassell, Chris Spedding, Nile Rodgers, Shawn Colvin, L Shankar, Sussan Deihim, Richard Horowitz, and Seal.

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