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dbx 376 Vacuum Tube Channel Strip

Designed for those who do not have the need, funds or space for a high-end console, channel strips aspire to offer big-desk features at a price aimed towards project studios. Enter the dbx 376 - a $599.95 channel strip with those features and then some.

Designed for those who do not have the need, funds or space for a high-end console, channel strips aspire to offer big-desk features at a price aimed towards project studios. Enter the dbx 376 – a $599.95 channel strip with those features and then some.
Product PointsApplications: Studio, broadcast, live sound

Key Features: Tube microphone preamp; three-band EQ; compressor; de-esser; digital outputs (AES/EBU and S/PDIF); balanced analog 1/4″ and XLR outputs; instrument input

Price: $599.95

Contact: dbx Professional Products at 801-568-7660 Web Site


+ Tube preamp character

+ Full complement of analog and digital I/Os

+ dbx type IV conversion


– No memory for pushbutton controls

– Two units can not be linked for stereo operation

The Score: A great front end for computer-based recording at a bargain price.

Vacuum tubes, or valves, are turning up regularly in new pro audio gear – and they remain a mainstay in the high-dollar, boutique preamp class. Whether or not the manufacturer’s claimed benefits are legit, there is no better place to inject a little voodoo than in between a microphone and a recording medium.

The dbx 376 is a channel strip that has a vacuum tube preamp section as its centerpiece, with a modern twist: it also has three-band EQ, a compressor, a de-esser, high resolution A/D converter and digital output.

The 376’s chassis takes up one rack-space and extends about eight inches deep into a rack. A part of dbx’s Silver Series, the 376 is outfitted with an attractive silver faceplate and satin silver control knobs.

There are three inputs on the 376: a balanced XLR microphone input, a balanced 1/4-inch line input on the back and an unbalanced 1/4-inch instrument input on the front panel. There is also a line switch that, when engaged, bypasses the microphone input. Using the front panel instrument jack overrides the back panel line input. These input features eliminate the need to constantly repatch based on your input source.

The 376 has a Drive control (+30 to +60 dB microphone and -15 to +15 dB for line), a four-segment LED meter, a -20 dB pad switch (microphone only), a +48 V phantom power switch, a phase switch, an insert jack and a low-cut switch that engages 12 dB per octave shelving EQ at 75 Hz. The vacuum tube in the 376 is a Phillips 6189W, which is comparable to a 12AU7 – a common guitar amp tube.

Contrary to the manual (which claims the unit has a three-band parametric EQ), the 376 has a three-band EQ with fixed-frequency shelving controls for low and high frequencies (80 Hz and 12 kHz, +/-15 dB) and a sweepable mid that ranges from 100 Hz to 8 kHz (+/-15 dB). Surprisingly, dbx includes an EQ clip indicator in this section-a nice touch.

dbx is well known for its compressors (I own several), so it makes sense that it would equip the 376 with one. The compression section is outfitted with threshold and ratio controls, a three-segment threshold indicator, an eight-segment gain reduction indicator, an over-easy knee switch and, in lieu of attack and release controls, a slow switch. The over-easy function makes the onset of compression more gradual, and the slow switch yields a longer attack time-important controls when recording vocal tracks.

Speaking of vocals, the 376 also includes a de-esser. There are two potentiometers that allow tweaking of frequency (800 Hz to 10 kHz) and depth amount. Last in the signal chain is the 376’s output-level control and a meter-select switch that allows you to choose between monitoring the analog or digital outputs.

The 376 has a number of controls associated with its conversion section. All of these controls are pushbuttons that illuminate in a variety of colors, depending on the parameter selected. There is a dither algorithm selection switch (SNR2, TPDF or none), a shape switch, a sample-rate selector (44.1, 48, 88.2 and 96 kHz), a word length selector (16-, 20- or 24-bit) and an output-format selector (S/PDIF or AES/EBU).

The conversion process used in the 376 is dbx’s proprietary Type IV. This process is quite remarkable, as it acts like a smooth limiter and provides a usable range above the linear A/D range. In a nutshell, Type IV utilizes the top 4 dB of the converter’s linear dynamic range to create a logarithmic overload region that allows high-level transients (that would normally clip other converters) to be adequately represented in just 4 dB. In other words, you can’t clip the A/D converter in the 376.

The 376 has both analog and digital outputs. The analog output is accessed through balanced XLR and 1/4-inch jacks, while the digital output shows up on S/PDIF (RCA coaxial) and AES/EBU (XLR) connectors. All connections are made on the unit’s back panel, which is also home to the power switch and a pair of BNC connectors for word clock in/out. A standard IEC A/C power cable is included with the unit.

In use

I have been producing a regionally aired, one-minute daily radio segment for the last year and a half. Each spot contains about 45 seconds of voiceover, some segue music (usually acoustic guitar), and occasional natural sound effects (birds, waves, etc.).

I record and edit the spots in Sonic Foundry’s Sound Forge on a Pentium II 400 MHz PC. This ongoing project seemed the perfect chance to put the 376 through its paces.

Before using the 376 in a session, I spent some time testing it out. I placed it in my rack directly above a MOTU 2408, which I use to route audio to my computer. I hooked the 376’s S/PDIF output to the 2408 and connected a Lawson L47 to the dbx’s microphone input. After powering up the 376, I applied phantom power and selected the proper sample rate, word length and output type using the front panel controls.

Using the 376 was a breeze. I never had to reach for the manual as the controls are sensibly laid out and well labeled. Using the EQ, compressor, dither and noise shape controls, I got a superb vocal sound that was intimate and full of detail. By boosting the drive control and lowering the output level, I was able to get a crunchy vocal sound – but not one that would make me want to stop using a Line 6 POD or guitar amp for such effects.

When used to record a female voiceover for the radio spots, the 376 was a stellar performer. The vocal talent was not a professional voiceover artist, and she had some mic control issues that needed addressing. With a little EQ, compression and de-essing, I was able to craft a warm and punchy voice sound, similar to those heard on National Public Radio (NPR).

As you might expect, the compressor on the 376 is a capable one. It handled transients in a smooth and transparent fashion. This, coupled with the Type IV conversion, should make for high-resolution recordings that make the most of the digital recording process. I did, however, miss the flexibility of attack and release controls. Although the slow switch is effective, it is not a substitute for these controls.

Later, I used the 376 to record some guitar parts for the same project. Using an Audio Technica 4051 pencil condenser, I achieved some great guitar images on tape … actually, on hard disk. The guitar was a bit boomy, so I engaged the low-cut switch, which cleaned things up nicely.

After rolling out some mids in the 700 to 800 Hz range, dialing up some light compression and tweaking the dither and noise shape controls, I got a guitar sound that was pleasing. It was warm and detailed, and it was all digital going to the computer.

One gripe I have with the 376 is with the pushbutton controls. As mentioned earlier, these buttons change color depending on your selection. For instance, the word length button lights red for 24-bit, green for 20-bit and goes off for 16-bit. This system works fine except for the fact that the unit has no retention capability. If you don’t use the default settings, you must go through and press all the buttons each time you power up the 376. I would also like to be able to link two units together for stereo operation/processing.


I applaud dbx on the creation of a product that utilizes the best attributes of analog and digital technology for a remarkable $599.95. Whether or not the vacuum tube enters into it, this unit’s preamp has a warm, “tubey” sound. Add to that a competent EQ, a great compressor, an ingenious conversion process with digital outputs, and you have a unit that is ideal for today’s computer-based DAWs.