Russ Long, a Nashville-based producer/engineer, owns The Carport recording studio. He is a regular contributor to Pro Audio Review.
With the introduction of the Octane, M-Audio once again proves that professional audio is not always synonymous with expensive audio. The Octane is an 8-channel microphone preamp that provides an ideal audio path from microphone signal through to any lightpipe-compatible device such as a hard disk recorder and/or digital mixer. Each of the 8 channels has its own input level control, pad and meter. The Octane's first two channels can act as high impedance instrument-level inputs, perfect for guitar, bass and keyboards. The last two channels offer M/S matrix encoding circuitry for mid/side stereo recording. The Octane even includes direct outs for each channel.
Product Points
Applications: Studio, project studio, broadcast, post production, sound reinforcement
Weighing 7.1 pounds, the 2U 5 inches deep M-Audio Octane costs $749. On the Octane's rear panel, a row of eight female XLR connectors provide input to the unit's eight microphone preamps. The preamps provide 50 dB of variable gain and a frequency response of 20 Hz - 20 kHz, ±0.11dB. The circuit's impressive specs reveal a signal-to-noise ratio of 120 dB (A-weighted), a dynamic range or 120 dB (A-weighted), and a THD+N of 0.00041% -107 dB, 1 dB below clipping, 22 Hz - 22 kHz. The preamp's input impedance measures 2.85 kohms or 3.600 kohms if the pad is engaged.
A row of eight 1/4-inch TRS connectors provide A/D (analog to digital converter) input. These inputs accept either balanced or unbalanced signals and have an impedance of 20 kohms (balanced) or 13.3 kohms (unbalanced). The inputs have a frequency response of 20 Hz - 20 kHz, ±0.04 dB and a signal-to-noise ratio or 110 dB (A-weighted). The dynamic range is 110 dB (A-weighted) with a THD+N: 0.00067% -103 dB, -1 dBFS, 22 Hz - 22 kHz.
A second row of eight 1/4-inch TRS connectors provides direct outputs for each channel. These outputs are half-normaled to the Octane's A/D line inputs, allowing them to function as eight independent channel insert sends. When a connector is plugged into the A/D line input, the signal from the XLR input is interrupted but when a connector is plugged into the line output, it is not. The maximum analog output (digital clip) with a 600 ohm output impedance is +26 dBu (balanced) or +20 dBu (unbalanced).
A pair of 75 ohm BNC connectors provide word clock I/O for synchronization to other digital devices. A TOSLink connector provides ADAT eight-channel digital output and a power jack accepts input from the Octane's 18VAC 3500mA power supply.
On the Octane's front panel, each of the eight channels is equipped with a mic level control that adjusts the input level of the channel's mic preamp, a pad switch that activates a 20 dB pad when pressed and a three segment LED input level meter. The green LED illuminates when the input level reaches -20 dB, the yellow LED illuminates when the input level reaches -10 dB and the red LED illuminates when the input level reaches -3 dB (0 dB is clipping).
Pressing the Phan 1-4 button activates +48V phantom power to Channels 1-4 and pressing the Phan 5-8 button activates +48V phantom power to Channels 5-8. Each phantom power button has a corresponding LED that illuminates when phantom power is activated.
The three position Sample Rate Selector switch determines the sample rate of the Octane's digital outputs. Selecting 44.1 kHz or 48 kHz sets the internal clock to the corresponding rate; selecting Ext locks the Octane's output to the sample rate being fed to the rear panel word clock input (an LED illuminates to confirm the clock is locked). The external word clock slave sync can range from 33 kHz to 59 kHz.
Two front panel mounted 1/4-inch jacks provide instrument input to the first two channels. When a 1/4-inch connector is plugged into Channel 1 or 2 Inst in, the XLR mic input for the corresponding channel is disabled. Two Instrument Level controls adjust the input level of the channel. The instrument inputs have a variable gain of 44dB and an input impedance of 3 Mohms. Their frequency response is 20 Hz - 20 kHz, ±0.03 dB and the signal-to-noise ratio is 133 dB (A-weighted).
Channel 1 has a low-cut filter (-12 dB/oct @ 80Hz) that is activated by pressing the Low Cut button. Channels 2, 4, 6 and 8 feature phase reverse switches that reverse the phase of the corresponding channels output. Channels 7 and 8 feature M/S matrix encoding. Pressing the M/S switch engages the matrix encoding, Channel 7 becomes the mid channel and Channel 8 becomes the side. The width knob regulates the apparent width of the stereo signal.
In Use
In designing this box, M-Audio wisely made the decision to give certain features only to certain channels thus keeping the price down while providing more features than any other mic pre in its price range. Even though phase reverse is only provided on even channels, instrument input is only provided on channels one and two and the high-pass filter is only available on channel one, the box can pretty much handle any situation with a little planning and preparation.
I found that the Octane's mic preamps sound quite flattering. When I received the unit I was about halfway through a month-long Christmas album that was using a combination of Focusrite, Daking and Gordon mic preamps. I immediately began using the M-Audio box for nearly everything and it amazingly held its ground. The producer I was working with was also pleased with the box's performance.
Over the last two months I have been able to use the Octane to record acoustic guitar and mandolin with a Sony C-800G, flute, oboe and sax with a Royer Labs SF-1A, vocals with a BLUE Cactus, electric guitar with a Royer Labs R-122 and several percussion instruments with Shure SM-57s, AKG 414s and an Audio-Technica 4047. In every instance I was pleased with its performance.
I was also pleased with the sound of the Octane's converters, though I did find that they sound substantially better when clocked to my Lucid Gen-X-96 clock rather than the internal clock. Clocking to the Lucid clock resulted in more depth and a cleaner more defined sound.
Unfortunately, the Octane only supports 44.1 kHz and 48 kHz recording. High resolution recording (88.2 kHz, 96 kHz, etc.) is still a rarity in my world so I don't find that too discouraging but anyone primarily working with higher sample rates or planning to make the move to high resolution recording soon should factor that into the equation when considering the Octane.
I was happy to see M/S matrixing as one of the Octane's features. I love recording using M/S stereo and had wonderful results using the Octane to record drum ambience using a Sony C-800G as the mid and a Coles 4038 as the side.
Summary
Frankly, I'm surprised that you can actually get a decent mic preamp for under $100/channel, especially one that includes analog to digital conversion, but M-Audio has proven that it's possible. Any financially challenged studio or engineer in need of multiple mic pre's should take a long hard look at the Octane.
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