The audio world is apparently based on the number eight. Consider, for example, 8-track modular digital multitracks (MDMs), 16-channel mixers, 24- and 32-track recorders, 48 and 96 kHz sampling rates — all are evenly divisible by the magic number eight. One of the first preamp manufacturers to accommodate that concept was PreSonus with its popular M80, an 8-channel mic preamp and mix bus that can serve as a convenient front end for MDMs or other 8-track recorders.
Now PreSonus has unveiled the DigiMax, a single-rackspace 8-channel mic preamp with a bevy of I/O options, including simultaneous digital and analog outputs (see Fig. 1). Designed primarily as a front end for digital recorders and digital audio workstations (DAWs), the DigiMax is also convenient for live recording applications. In this review, I'll investigate what this powerful box has to offer.
The DigiMax employs the same preamp design as the highly regarded PreSonus MP20, M80, and VXP, incorporating eight Class A discrete input buffers followed by a dual-servo gain stage providing 60 dB of preamp gain and 30 dB of headroom. Each channel provides 48V phantom power, a 20 dB attenuation pad, and two distinctive features: a Dual Domain limiter and an equalizer circuit called EQ Enhance. Three LEDs at the top of each channel section provide visual feedback indicating signal present, clip, and limiter active. In addition, each of the DigiMax's first two channels provides a polarity-reverse switch and an unbalanced ¼-inch instrument input. The latter allows the unit to function as a direct injection (DI) box for guitars, keyboards, and other instruments.
The limiter is dubbed Dual Domain because it employs both standard peak detection (the type used in most brickwall limiters) and root mean square (RMS) detection (more commonly found in compressors). The unit uses high-ratio RMS compression to handle the bulk of the limiting tasks and reserves the peak-limiting portion to catch fast peaks and thus protect the input of the A/D converter from clipping.
The EQ Enhance feature engages a bell-type EQ centered at 1 kHz and extending from 250 Hz to 5 kHz. When it is engaged, it cuts 4 dB at the center frequency.
Completing the front panel are two backlit buttons on the unit's far right: one labeled Sample Rate and the other, Ext. Clock. The Sample Rate button toggles to select from three sampling rates — 32, 44.1, and 48 kHz — each with a corresponding LED.
The DigiMax's rear panel provides eight mic inputs on Neutrik combo connectors and eight balanced ¼-inch TRS analog outputs (see Fig. 2). The rear panel is also where the 48V phantom-power switches are — inconveniently — located.
The DigiMax provides digital output through an ADAT Lightpipe port (which carries eight channels) and a 9-pin connector that outputs signals in AES/EBU or S/PDIF formats. Accessing the S/PDIF or AES/EBU output requires, respectively, the DM006 or the DM007 9-pin breakout cable ($39.95) available from PreSonus. Either cable provides four stereo connectors for a total of eight channels (see Fig. 3). The DigiMax is preconfigured for AES/EBU output, but you can switch it to S/PDIF by resetting jumpers inside the unit.
Digital output can operate at 32, 44.1, or 48 kHz sampling rates. Bit depth is fixed at 24 bits. No dithering of the output is provided (despite the manual's assertion that it is — a misprint, according to PreSonus), so connecting the DigiMax to a 16-bit device results in a simple truncation of the last eight bits of data. Word-clock I/O is provided, and the DigiMax can automatically sync to incoming word clock or a digital-input signal through its BNC connectors, which are also on the rear panel.
A cool DigiMax feature is its ability, when fitted with a breakout cable, to simultaneously output 24 channels: 8 analog and 16 digital. That solves the latency problem inherent in DAW recording by letting you monitor directly from the DigiMax's analog outputs, thus avoiding any signal delay, while the digital outputs feed the DAW. That feature alone could put the DigiMax at the top of the list for anyone who records real instruments (as opposed to those who work only with MIDI sound sources).
The simultaneous analog and digital outputs also make the DigiMax great for live recording. For example, you could use the ADAT Lightpipe to feed an MDM's digital input while sending an identical signal to the front-of-house mixer using the DigiMax's TRS analog outputs.
The DigiMax has an external power supply, which clearly helps account for the unit's impressively low noise specification. However, it's not your typical wall-wart or line-lump power converter. Rather, it is a heavy-duty ⅓-rackspace unit that can be rackmounted using the optional PSRA rack adapter ($29.95), which can hold three DigiMax power supplies.
Often you can't tell if a device's sonic signature is desirable until it accumulates on several tracks. For instance, if you record 20 or 30 audio tracks through a lame signal path, the cumulative result becomes quite noticeable. The same is true for recording through a great signal path, except that the cumulative result is good rather than bad. It all adds up, whether for you or against you.
The preamps in the DigiMax sound good and full over a broad frequency range. They also have little inherent noise, because of their capacitorless design.
My studiomates and I recorded with the DigiMax for a couple of months while working on a variety of projects for Hal Leonard Publishing, Carnival Cruise Lines, and several theater shows. We set up two rooms, one with my normal tracking rack and the other with the DigiMax. (My tracking rack consists of two channels of Neve 1272 preamps, two Empirical Labs Distressors, and a stereo Nightpro EQ3-D.)
Although we often move my tracking rig from room to room when recording critical tracks, it stayed put during the period in which I evaluated the DigiMax. If we needed to cut vocals or do MIDI transfers in the room with the DigiMax, we did so without hesitation. The DigiMax worked great as a digital A/D front end for MIDI transfers into the computer, and it also provided quality preamps for vocal and other critical recording.
That is not to say that the DigiMax sounded as good as my tracking rack; after all, one channel in my rig costs about $3,000, as opposed to $212 per channel for the DigiMax (not to mention that the DigiMax includes A/D converters). It was a testament to the merits of the PreSonus preamps that we trusted them enough to use them on real-world projects in which quality was essential. Playing with a unit for the purposes of writing a review is one thing, but actually using the unit on professional projects is something else entirely. Thankfully, the DigiMax preamps passed with flying colors.
The bonus features on the DigiMax were less to my liking. For example, the Dual Domain limiter's threshold, which is controlled by the outer dial of a dual-concentric pot (the inner pot controls the channel's gain), was difficult to set properly because there is not much of a sweet-spot range to work with. Up to a point, the limiter sounded as though it wasn't doing much at all; then suddenly, when I turned the knob only slightly more, it squashed the signal in an unpleasant way.
According to PreSonus, the limiter has two thresholds with a 6 dB difference between them. You get only light compression at lower threshold settings. When the signal hits the second threshold, the harsher peak limiting sets in. Because the threshold is interactive with the gain amount, some experimentation is necessary to find the proper settings for the desired effect. However, I never achieved a sound that I liked with the limiter; after a few days, I simply stopped using it and was quite happy thereafter.
I stopped using the EQ Enhance feature, too, because engaging it on a channel carves out a 3 dB hole from 250 Hz to 5 kHz, effectively gutting the frequencies in which most of the music lies. I did not find a single instrument, live or MIDI, that sounded better with the EQ Enhance button engaged. For that reason, I think a tamer midrange dip — say, a 1.5 dB cut at 630 Hz with a much narrower bandwidth — would better serve the DigiMax. Perhaps PreSonus could use the slot to install a highpass filter, an airband boost, or a channel mute.
LOTS TO OFFER
The PreSonus DigiMax is an affordable, versatile unit that excels at its core duties: mic and instrument amplification and A/D conversion. Its Class A preamps sound great, and the simultaneously available analog and digital outputs provide an elegant solution for the vexing problem of signal latency, making the unit an excellent choice as a front end for digital recorders and DAWs. The unit is ideal for live recording, too, and it can function as a 2-channel DI box.
The DigiMax's limiter and EQ enhancer circuit are of limited use. The unit does not support 88.2 or 96 kHz audio, which may limit its appeal for forward-looking digital recordists. Still, the DigiMax occupies its own audio niche, providing useful capabilities that no other single box offers. If you're looking for an 8-channel preamp with digital outputs to use as an A/D path for a DAW or digital recorder, the DigiMax has you covered.
mic preamp and A/D converter
FEATURES4.0EASE OF USE4.0AUDIO QUALITY4.0VALUE4.0
RATING PRODUCTS FROM 1 TO 5
PROS: Eight channels of excellent-sounding Class A preamps. 48V phantom power and 20 dB attenuation pads on each channel. Polarity-reverse switches and unbalanced ¼-inch instrument inputs on first two channels. Flexible analog I/O and digital output with 24 simultaneously active outputs. Supports 24-bit audio at 32, 44.1, and 48 kHz. Offers word-clock I/O.
CONS: Limiter feature squashes audio too easily. EQ Enhance feature carves out midrange too drastically. Phantom-power switches inconveniently located on rear panel. Does not support 88.2 or 96 kHz audio.
Audio Channels8Analog Inputs(8) balanced XLR/TRS Neutrik combo (mic); (2) unbalanced ¼" (instrument)Analog Outputs(8) balanced TRSDigital Outputs(1) ADAT optical (8 channels); (1) 9-pin (8 channels), selectable AES/EBU or S/PDIF (optional breakout cable required); (1) BNC word clockSynchronization(2) BNC word clock (input and output)Frequency Response20 Hz-50 kHzTotal Harmonic Distortion + Noise<0.009%Noise Floor-94 dBuSignal-to-Noise Ratio>98 dBAnalog Dynamic Range>120 dBHeadroom+24 dBuMaximum Gain+50 dBuAttenuation Pad20 dBLED Meters(1) signal present (-20 dBu); (1) clip (+22 dBu); (1) limiter activePhantom Power+48V (individually switchable on back panel)Polarity Reversechs. 1-2Sampling Rates32, 44.1, and 48 kHz (selectable)Bit Depth24-bit (fixed)Power Supplyexternal, ⅓-rackspace (rackmountable)Dimensions1U × 7" (D)Weight15 lb.