Audio Toys Inc 8MX2

Hugh Robjohns takes a look at yet another studio unit designed to partner the new generation of digital 8‑tracks, this time from a company new to the UK market.

The most popular recording format today is the 8‑track digital tape machine. Professionals in broadcast and post‑production generally seem to use the DA88 format, while the musical fraternity seems to prefer the ADAT system. In both cases, one of the most common problems is that of finding a suitable microphone preamplifier which can feed all eight channels of the machine, as well as letting you build a monitor mix to hear what's going on.

Audio Toys Inc of Columbia, USA, have produced a purpose‑designed preamp/mixer to meet these very demands, using circuitry derived from their Paragon series of mixing consoles. The 8MX2 provides eight channels of microphone preamplifiers (with peak limiters), feeding directly to the multitrack tape machine, plus a stereo monitoring system with feeds from the mic signals (pre‑ or post‑limiters), the multitrack returns, or a stereo tape machine return, plus a stereo recording mixer with its own level and pan controls.

The Box

The 8MX2 is housed in a sturdy, 19‑inch, 1U rackmounting box, with a bright and distinctive red front panel. The rear of the unit is festooned with socketry — eight XLR microphone inputs to the right, six quarter‑inch jacks in the centre, and four D‑sub connectors towards the left, finishing the collection with an IEC mains socket on the extreme left. The review model did not carry a CE approval mark.

The electronically‑balanced mic inputs each have two miniature toggle switches associated with them. The first provides 48V phantom power, and the second provides an earth‑lift facility — particularly useful if the 8MX2 shares microphone splits with another mixer. The microphone inputs have 20dB of headroom and maximum input levels of +24dBu.

The collection of six TRS jack sockets provide the monitoring system inputs and outputs: loudspeaker/headphone monitoring and mixer outputs for recording on a 2‑track machine, plus a 2‑track return — all in stereo, of course, and all electronically balanced. The two 25‑pin D‑sub connectors provide balanced line‑level inputs and monitoring returns, and are wired for compatibility with Tascam DA88s and Fostex CX8/RD8 machines, although suitable cables are also available for interfacing the 8MX2 with Sony PCM800s, Panasonic MDA1s, Roland DM800 and Alesis ADAT machines, amongst others. Two 9‑pin D‑sub connectors provide a means of interconnecting the monitoring busses between multiple 8MX2 units, to allow elaborate systems to be constructed — offering, say,24‑track recording capabilities whilst allowing easy monitoring from a master unit.

Twiddly Knobs

The front of the 8MX2 is a mass of dual‑concentric rotary controls (18, to be precise) and small push buttons (27, no less!). Unfortunately, squeezing this number of controls onto the limited real‑estate of a 1U box has resulted in rather cramped and confusing labelling, although once you've become familiar with the control functions, the labels become much less important.

Each of the eight channels has a pair of dual‑concentric rotary controls and four push buttons. The microphone input gain is set by the blue‑capped inner knob of the lower control, which has a fine, 41‑position detented action and a range of 0‑65dB. In most applications I'm sure this gain range will be perfectly acceptable, but personally I would have preferred a slightly wider gain range to accommodate quieter sources or the more distant microphone techniques. As the input is capable of handling signals up to +24dBu, an input pad is not necessary. The bottom two push buttons relate to the microphone signal: the upper of the two reverses the polarity of the microphone signal, and the lower one makes the channel available on the monitoring system.

The outer knob of the lower pair of controls sets the peak limiter threshold for the channel, and since overloads on digital formats are so unpleasant, the inclusion of independent peak limiters on each channel is an excellent idea. The threshold is continuously variable between +24dBu (effectively out of circuit) and +4dBu, and the ratio is said to be infinity:1. No information was given about the attack and release times, but they are clearly extremely short — in practice, the limiter provides a useful and effective overload‑prevention system, although care should be taken to set it such that it really does only operate in emergency situations.

The upper set of concentric controls provides level and pan facilities for the stereo mixer output, which are pretty self explanatory. A push button directly below these knobs routes the signal to the mix buss, whilst another to the left selects the input to the level control. The default is the microphone signal, but pressing the Return button selects the corresponding multitrack return signal, allowing the 8MX2 to be used to handle overdubs as well as straight recordings.

Stereo Mixer

The stereo mixer couldn't be simpler: the eight inputs are selected between multitrack returns and microphone signals (after the recording gain and limiter thresholds have been set), panned and balanced appropriately, and passed on to the master level and balance control at the right‑hand side of the unit.

I don't understand why Audio Toys Inc felt it necessary to include a balance control on the stereo recording feed — it seems to me that this would have been more appropriate on the headphone/loudspeaker monitor output, which presently has no such facility — strange...

With the 8MX2 as supplied, the 2‑track return is only available to the monitoring system, but a couple of internal jumpers allow the return signal to feed into the mix buss if desired. In this mode, the return is at unity gain (there is no provision for any level control) and the idea is to make use of this input as an effects return for the stereo mix. This could prove to be a useful facility for a reverb return, although care should obviously be taken to avoid returning the output of the stereo mix recorder back into the mix buss.

Monitor Section

The monitoring section on the extreme right of the front panel consists of a pair of LED bargraph meters, a headphone socket, a monitor level control and three push buttons. The level control speaks for itself, but the metering is a little unusual. One 10‑segment bargraph provides a level meter, while the other shows the amount of gain reduction applied by the selected channel's limiter.

The basic arrangement is that the monitoring section allows the user to audition each input channel individually, to set up the gain and limiter. In this case, the level meter shows the output level for that channel (from ‑3 to +24dBu in 3dB steps), whilst the other meter (labelled Atten) shows any gain reduction from the limiter (scaled from ‑2 to ‑20dB). A push button to the left of the section causes the channel cue signal to be taken from either pre‑ or post‑limiter processing or from the multitrack return signal.

When no channel is selected to feed the cue monitor system, it defaults to the output of the stereo mixer, the level meter showing a mono sum (left plus right minus 6dB) of its output. A push button adjacent to the monitor level control allows the 2‑track return to be monitored in stereo.

The manual carries warnings that the headphone output is only suitable for driving high‑impedance headphones, and not the common domestic 8Ω types. I don't understand why, in a mains‑powered unit, the headphone amplifiers could not be designed to drive all headphone types, and I didn't have any low‑impedance models to find out what happened! With 400Ω and 2kΩ headphones, however, there was plenty of output level.

Conclusion

The 8MX2 is a useful piece of equipment for any DA88 owner. If you wish to make multitrack recordings direct to DA88, but with the advantage of a stereo monitor mix, this is the tool for the job. Generally well designed and with good sonics, it is really only let down by one or two bizarre design features, such as the balance control on the stereo mixer output. In use, it proved reliable, quiet, easy to set up and, above all, transparent (assuming that the limiters were not active). I found the 8MX2 an indispensable partner for the DA88.