ART Pro VLA II Compressor Review.

ART Pro VLA II Leveling Amplifier and M-Audio Fast Track 8R.

Today was a joyous day in my little world. A little box (actually it was a pretty big box, and quite heavy at that) arrived at my door this morning from our friends over at Sweetwater.com.

The ART Pro VLA II Leveling Amplifier is a rather inexpensive tube driven two-channel compressor/limiter. Vacuum tubes are all the rage lately, (when I say lately, meaning the past decade or so) and nearly every professional audio company seems to be cashing in on the craze. The audio recording world has been no exception. Many feel that digital recording sounds "cold" or "sterile," and many companies are adding tubes in the signal chain to add some "warmth" to the sound. Now I’m not completely sure how grounded these claims are, being that any quality analog piece of recording equipment, solid state or valve, will have it’s own sonic character. Solid state mic pres, such as ones made by API or Neve, or compressors such as the dbx 160a or the famous UREI 1176 will have plenty of warmth to go around, but we’ll save that discussion for another time.

First Impression

In my little world, the arrival of this ART leveling amplifier is nothing short of a godsend. As a home recordist, I have been using plug-ins for quite some time, but through experience found that working with analogue equipment was more inspiring and easier to get the sounds that I heard in my head. I heard a many good thing about the VLA II and decided to pick one up myself. Unwrapping the unit revealed a quality piece; it had detented pots with well marked descriptors and values, two large analogue VU meters with selectable input/output metering, gain reduction and output level displayed via LED meters, a bypass switch per channel to take the compressor circuit out of the signal chain, XLR and quarter-inch TRS input and output jacks on the back, all housed in a study, stamped metal chassis.

Totally spiking the output meter. Rawr!

The controls, per channel.

Without ado, I connected the VLA II to the I/O of my M-Audio Fast Track 8R interface and began running 2 Track stereo mixes through the unit. My immediate reaction was, “Boy, this thing really colors the sound!” And it does. It rolls a bit of the high end off and even with the Ratio set at 2:1 (the lowest setting) and Input Threshold set to have a gain reduction of only about 1dB to 2dB, compression was quite audible. With a little tweaking of the attack and release times, the compression was tamed and sounded very smooth and pleasing. The overall character however sounded a little too "tubey." Even when I backed off both the input and output gain, I would run into some slight distortion in sound of fizziness on the lead vocal.

Now I’m not completely sure where the sound coloration is taking place, but my guess is that the tubes have something to do with it. Being that this unit is advertised as a "vactrol" type compressor (in other words, a compression circuit that utilizes an optocoupler) chances are the tube itself has little to do with the actual signal attenuation, and more to do with the output gain stage (output level). This however still gives the tube plenty of room to impart it's own sonic character to the overall signal.

Diving In

Opening the unit up revealed the presence of two 12AT7 tubes, one for each channel. 12AT7s are lower gain (but higher current) than the more popular 12AX7 seen in guitar amps. Upon inspection I found the stock tubes to be Ruby Tubes. Being that the VLA II is the only unit I have tried with these tubes installed, I cannot make any reliable judgment on how good these tubes are. Poking around my parts drawer, I luckily found two Tung Sol 12AT7s and quickly popped them in. I love the way Tung Sol tubes have a nice, bright chime in guitar amplifiers, and I hoped that they would sound about the same in the VLA II.

Replacing the stock tubes with any high quality type (in this case a pair of Tung Sol) will help extend the frequency response, increase headroom, and help with overall clarity.

To my luck, they did! I wouldn't go so far as to say it was a "night and day" difference, but much of the higher frequencies that were attenuated with the stock tubes did not occur with the Tung Sols. They were significantly clearer, the bass tighter and more defined, and had much higher headroom... they didn't even distort if I drove the output level very hard (the picture where I'm spiking the output meter). The addition of the Tung Sol tubes really helped the unit out, but I could only imagine that any quality tube from RCA, Phillips, GE, Mullard, or GT would help the output stage immensely. Now don't get me wrong, I'm not knocking the Ruby Tubes at all. I think possibly the VLA II is designed with a lower plate voltage that in turn lowers the headroom, and maybe the Ruby Tubes are less adept to handle such conditions, but that's only a theory.

Concluding Opinion

The ART Pro VLA II as delivered is a good compressor/limiter especially if you want to add a certain vintage character to your recordings. It immediately gave more fatness to the bass frequencies, my guess about 200Hz and below. The only caveat is that some of the high end (especially above 9kHz) I felt was sacrificed, and the mids were not very defined overall. This is not however a criticism of the sound; it is still very useable and with some careful EQ treatments on the front end, will add just enough secret sauce to your mix.

With a higher quality tube replacement, I give the VLA II two big fat thumbs up. None of the high frequency gobbling, much better headroom, more defined mids, and bigger bass without sounding muddy or messy. What was a "character" compressor becomes a solid all around performer good for single sources and 2 Track stereo mixes alike.