Test Drive: Voxbox from Manley Laboratories

voxbox-front-panel

By Steve Cunningham

Voice processors that combine a mic preamp, a compressor, some EQ, and a limiter have become quite popular. They give you all the tools you need to produce great voice tracks in one box, without all the connection hassles of using a mixer and outboard processing. In addition, the quality of the individual sections in a vocal processor is usually better than what you’ll find in a typical mixer and outboard gear combo, and the whole business is much easier and more convenient to use.

Having said that, describing the Manley Voxbox as just a vocal processor is a bit like saying the Porsche Boxster is a good transportation car. The all-tube Voxbox is not just good, it’s astonishingly good. In fact, every audio block in this product is astonishingly good.

The Voxbox incorporates several existing Manley designs into one package, including their mic preamplifier, optical compressor, and Pultec-style passive EQ. To this, they have added an optical de-esser with a limiter setting, and they’ve packaged it all with enough input and output connectors to make it flexible.

The VoxBox is designed and built by Manley Labs in Chino, California. For those of you not familiar with the Manley brand, the company has been building all-tube hi-fi and pro audio gear since the 1980s, and Manley equipment is used by some of the best recording studios and mastering houses in the world.

Manley products are not inexpensive, and with a list price of $4000, the Voxbox is no exception. But if your livelihood depends on the sound of your voice, then you need to read on—this device will improve your life.

VoxBox-Block-Diagram

SIGNAL FLOW

The Voxbox is organized in two sections. The first section contains the compressor and mic preamp, and I mention them in this order for a reason. The input signal is first sent through a passive rumble filter, and then through the INPUT attenuator. From there, the signal hits the passive 3:1 compressor, which relies on an opto-isolator to do its work. The compressor has no amplification stage, and hence adds no noise. The signal then goes to the mic preamplifier, which adds between 40 and 50 dB of tube-driven gain.

Normally you connect your microphone first to a preamp, and from there to a compressor. By reversing the order of these audio blocks, the Voxbox actually reduces the possibility of clipping the mic pre by feeding it a signal that is already compressed.

The second section of the Voxbox contains the EQ and the de-esser/limiter. The EQ is a passive 3-band design, with bands for low frequency boost, midrange cut, and high frequency boost. These are passive equalizers, with nothing but a capacitor, an inductor, a rotary switch, and a conductive plastic pot in the signal path for each of the bands. There are no tubes in the EQ, and definitely no ICs or transistors. Once again, the result is an EQ that adds no noise.

After the EQ, the signal hits the de-esser which is also passive, and uses another opto-isolator to control a passive notch filter. You can select one of four fixed “ess” frequencies set at 3K, 6K, 9K, and 12K, or you can select “LIMIT” which switches the notch filter out, leaving a full range 10:1 limiter engaged. The final stage is a tube line amplifier, which compensates for any loss created by the passive EQ circuitry and allows the Voxbox to drive long cables from its outputs.

Input signals can be at mic, line, or instrument level, with XLRs for the mic and line inputs, and a 1/4" jack on the front panel for instrument-level signals.

Comments (0)

There are no comments posted here yet