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Aphex Model 1788

Remote-controlled Mic Preamp By Hugh Robjohns
Published August 2001

FROM A DISTANCE

Aphex have provided an elegant way to avoid the detrimental effects of long cable runs on delicate mic signals. Hugh Robjohns evaluates the Model 1788.

A couple of hundred feet of cable can make a big difference to the quality of a microphone's output signal — high‑frequency losses, poor transient response and increased input noise being the main side effects. Therefore, it makes sense in any situation where there is a large physical distance between mic and mixer to place preamps as close as possible to the mic, allowing the signals to be sent to the mixer at line level. However, to do this successfully, you need also to be able to control these preamps remotely.

The Aphex 1788 is designed precisely for such applications, and offers XLR inputs for eight channels of mic preamplification. Two sets of analogue line‑level outputs are available simultaneously, one set on eight XLRs and one set on a 25‑pin D‑Sub connector. A digital output option can be fitted, and this further bolsters the output count with no fewer than three sets of simultaneously active digital outputs — AES‑EBU and TDIF via 25‑pin D‑Sub connectors, as well as ADAT optical.

The front panel is roughly divided in two, with the left half being given over to status LEDs and metering for each of the channels, under which are Channel Select buttons. All indicators and meters can be viewed over the remote control interface. Selecting one or more channels allows parameters to be modified with the illuminated buttons and rotary encoder to their right. These buttons cater for Mute, +48V Phantom, 26dB Pad, 75Hz Low Cut, Polarity Reverse and Enable Limiter, and a further button allows the encoder wheel to alter either the input gain (from +26 to +65dB), or the maximum peak levels of the main and auxiliary analogue outputs (between 0 and +24dBu). The 1788's peak limiting system is of the same innovative design found on other Aphex mic preamps, providing over 20dB of overload protection, and allowing near‑ideal use of available bit resolution if converting to digital.

All of these functions may be controlled remotely, over MIDI, RS232 or RS422 interfaces, although the protocol in all three cases uses a MIDI instruction set. Any equipment capable of generating MIDI data can therefore be used as a remote controller for the 1788, though Aphex manufacture a dedicated 1788R controller panel similar in looks to the Model 1788, as well as a bespoke PC software control utility. A further RS422 output allows up to 16 units to be daisy‑chained from a single controller. In addition to the remote control facilities, the 1788 can also store snapshots of its settings internally, usefully extending the facilities of many budget digital desks which don't have the ability to recall analogue input gain settings.

The remaining front‑panel controls cater for the eight‑channel 24‑bit digital output option. The conversion can be clocked internally at 44.1kHz or 48kHz, or from an external AES‑EBU or word clock input. An AES‑EBU clock output is on a further XLR.

After the digital control section is a headphone socket with level control and channel selector, and an internal test tone generator which may be allocated to any channel output and set to either 0dBFS (peak level) or ‑20dBFS (nominal signal level).

Verdict

The preamps exhibited a nice clean sound, as you'd expect from the wide, smooth frequency response and low noise floor. Distortion and crosstalk figures were also excellent. The A‑D converters were of good quality, and the limiter system was difficult to catch out in normal use. As for the control options, I was supplied with both the PC program and the 1788R panel, and they both worked reliably, with little impression of processing delay.

The Aphex Model 1788 provides a lot for the money, and beyond its obvious live uses, it would also be be useful in large recording installations, such as those recording orchestral music. In addition, the onboard snapshot facilities could be very useful in studios based around digital consoles, especially where a very fast turnaround for projects is required.

Pros

  • High‑quality mic preamps.
  • Innovative and effective input limiters.
  • Flexible analogue and digital outputs.
  • Multiple remote control interfaces.

Cons

  • Relatively expensive

Summary

This is a great‑sounding and flexible option for anyone who's after remote preamplification, though at a price.

Published August 2001