Presonus combine their respected analogue and digital technology in this affordable ADAT-equipped preamp.
While DAW systems are wonderful things — and most of us wouldn't dream of going back to our hardware days — many of the audio interfaces on the market have a frustratingly small number of inputs when we're faced with recording 'real' bands. Recording just a drum kit alone might require more than eight mic inputs, for example. Fortunately, though, a number of manufacturers include ADAT ports on their interfaces so that you can increase the interface's analogue I/O count by adding an ADAT expansion unit.
There are now a few such units on the market, from the likes of Alesis, M‑Audio, Focusrite and Behringer, and several also include ADAT outputs, in addition to the inputs. PreSonus, a company respected for both their analogue and digital designs, also feature in the list, with devices such as the DigiMax FS. The DigiMax D8, reviewed here, is their most recent addition to the list.
This 1U-high, rackmounting device features eight of PreSonus' class‑A XMax mic preamps, plus 24‑bit A‑D converters that generate ADAT-format digital output, allowing it to be used with any interface accepting an ADAT input. There's no option to add ADAT inputs to the unit itself, but PreSonus have other products that give you that — and if you only need extra inputs and plan to monitor in stereo, it means you don't pay for something you don't need.
All eight preamps have the same gain‑trim control, a 20dB pad button and 48V phantom power (separately switchable for pairs of channels), plus LED metering. Two additional instrument inputs (on channels one and two) are located on the front panel for ease of use with electric guitars and basses that have passive pickups. Each preamp also has its own balanced TRS analogue output jack on the rear panel, so if you're working with hardware recording gear and you have eight free line inputs, you can still put the DigiMax D8 to good use, as the cost per channel is actually very low — even if you don't need the digital output. There's a word-clock input on a standard BNC connector for external sync purposes, but the DigiMax D8 can also be synchronised via the ADAT connection.
To support sample rates beyond 48kHz over an ADAT connection, the SMUX protocol (which halves the available number of channels to allow up to 96kHz, and halves it again for 192kHz, using two ADAT ports) must be used. However, that doesn't feature on the D8, so the only sample‑rate options here are 44.1kHz and 48kHz, selected via a button on the front panel. Status LEDs in this section indicate both the internal or external sync status and the sample rate (when set to Internal Sync).
The layout of the D8 is very straightforward, with the gain trims, pad switches and four‑section LED metering on the front panel along with the two instrument inputs. All eight mic input XLRs are on the rear panel, alongside the eight balanced TRS jack outputs, the word clock BNC socket and the ADAT lightpipe output port. Given that there's no ADAT input, the DigiMax D8 must be used as the clock master in the system, with the audio interface set to external sync, or synchronised via its own word-clock input. Four phantom‑power buttons are available on the rear panel, which is a somewhat impractical place to put them, one between each pair of mic input XLRs. Mains comes in on a rear-panel IEC connector and the mains switch is next to it, which, again, makes it difficult to access once the unit is in a rack.
The XMax discrete-component preamplifier runs on power rails of 30V, which is around twice the norm for IC‑based designs, thus allowing the designers to build in more headroom. While excellent IC (Integrated Circuit) preamplifier chips are available, the best ones are quite expensive, and there's something endearing about the simplicity of a good discrete design. As is the case with the vast majority of discrete preamps, this one uses class-A circuitry, with a frequency response that's flat within ±0.5 dB from 20Hz to 50kHz, and only 3dB down at 150kHz. THD+N noise (unweighted, 1 kHz @ +4 dBu output, unity gain) is better than 0.003 percent, and the equivalent input noise (EIN) figure is ‑126dBu, with 55dB of gain and measured from 20Hz to 22kHz. The gain‑control range is 60dB, with maximum input signal handling capacity of +14dBu. On paper, then, the DigiMax D8 looks pretty well specified... but how does it work in practice?
Connecting and setting up the DigiMax D8 was no problem: it did exactly as expected, and was up and running within seconds of having plugged in the ADAT lightpipe. I used it as the clock master to my M‑Audio ProFire interface, and first made some test vocal recordings using the DigiMax D8, my Universal Audio Solo 110 and the preamps in my M‑Audio interface.
All preamps have a character, and you can't tell what the sound will be like just by looking at the distortion spec or the frequency response, but as I expected, the more expensive (on a per-preamp basis) Solo 110 produced the most transparent and detailed sound. The M‑Audio preamps came close to the same general tonality, albeit sounding a hint less refined. By contrast, the DigiMax D8 preamps had a generally smoother sound. The high end took on a polished quality, which I rather liked: a slight 'Galaxy Chocolate' smoothness which might be useful in offsetting the harshness of non‑esoteric converters or slightly less than optimal DAW plug‑ins. I'm not going to say it's better or worse than the preamps I compared it with, because I think that would be misleading, but it is subjectively a little different, and I liked its classy smoothness.
When you consider the price per mic preamp, the DigiMax D8 is great value. It also offers fuss‑free operation and a smooth, musical sound. The D8 works with any device that has an ADAT input port — or you could use its line outputs to connect to an analogue mixer, or a recorder or audio interface with only line inputs. Other than the somewhat inconvenient positioning of the power switch and phantom-power buttons, I really can't fault this device at this price.
The M-Audio Octane is perhaps the D8's nearest direct competitor. More expensive and fully featured is RME's Octamic D. If you want ADAT in and out, the Behringer ADA8000 is significantly cheaper — although there may be a trade‑off in terms of quality. Closer in price to the PreSonus is the Focusrite OctoPre LE, again with its own sonic signature, and again offering both inputs and outputs, but you need to pay extra for the ADAT option. Higher up the price range are products such as the 'full‑fat' OctoPre, which is about twice the price of its sibling.