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Aphex 1788 Eight Channel Microphone Preamplifier

Occasionally, a manufacturer offers a product that is not only innovative, but has multi-use applications, ease-of-use, loads of functions and great sonic characteristics. Aphex's new Model 1788, a quality eight-channel remote-controlled microphone preamplifier, is just such a product.

I first learned of Aphex, a name that has been around since 1975, when I discovered the Aural Exciter. Aphex is a company known for providing quality signal processing at a good price point.
Product PointsApplications: Studio recording; sound reinforcement

Key Features: Five separate blocks; eight channels with separate gain readout; polarity reverse; 75 Hz low cut; 26 dB pad; 48 V phantom power; and mic output limiter

Price: $5,000; TASCAM TDIF DB-25 connector option: $1,000

Contact: Aphex at 818-767-2929 or visit the company web site.


+ Well-designed

+ audio quality

+ Easy to use

+ Flexible


– Runs warm

The Score: This is a great sounding mic preamp that will bring your audio package to the next level
Occasionally, a manufacturer offers a product that is not only innovative, but has multi-use applications, ease-of-use, loads of functions and great sonic characteristics. Aphex’s new Model 1788, a quality eight-channel remote-controlled microphone preamplifier, is just such a product.

The 1788 provides remote control of all its functions using MIDI protocol. I am always looking for products to improve the sonic characteristics of the microphone and minimize equalization required – the Aphex 1788 responds to this call exceptionally.


The Aphex 1788 ($5,000) is 3.5″ high, 19″ wide and 13.25″ deep. It weighs in at 14 lb and occupies two rack-spaces. The front panel of the Model 1788 is arranged in five separate blocks (local, control, digital, monitor and test). The local block includes the individual channel status readouts. At the top of each channel is a two-digit gain readout LED that shows the input or output gain setting, depending on the status of the gain select button. Below that, on the right side, is a vertical 12-segment LED meter that indicates the available peak headroom, in 4 dB increments from 0 to 44.

On the left of the LED meter are several key functions: polarity reverse, 75 Hz low cut, 26 dB pad, 48 V phantom power and microphone output limiter. An associated LED lights when any of these functions are being used for each channel.

Buttons and a rotary knob on the right of the eight-channel display engage or adjust these indicators. Under each of the eight channels is a channel select button.

Located to the right of the local block is the control block, which selects communication ports and data rates. The Aphex 1788 using MIDI protocol via the RS-232, RS-422 or MIDI control ports controls up to 16 units at once. The RS-232 port is a three-wire, full duplex connection that can connect to a PC with runs between 50 and 100 ft. A Windows 95/98 remote program provides easy and maximum control of the Model 1788. The RS-422 is a full duplex differential transmission capable of runs up to 4,000 ft. A total of 128 channels of mic preamplification can be used with one control link.

The adjust button in this section selects options for the functions (MIDI, set port, local control). A six-digit global status readout display is located next to an adjust button.

The digital block is an optional module that includes an AES/EBU dB-15 digital output. It is possible to send all eight channels directly to a digital recorder or console. An ADAT digital connector is also included. A TASCAM TDIF DB-25 connector is available as an option ($1,000) for direct connection to digital recorders. This option also sets the synchronization source and sample rate.

A clock button determines either the internal or an external clock as a synchronization reference. Internal clock rates can be set to 32 kohm, 44.1 kohm and 48 kohm. The monitor block makes it possible to monitor each channel separately through headphones. The test block is used to adjust system levels with a 700 Hz test tone.

The Aphex 1788 rear panel consists of a power receptacle that works with a voltage range of 80 to 280 VAC. The eight XLR male input connectors are transformer-balanced with Jensen transformers. The output section provides two separate analog outputs per channel, eight servo-balanced XLR-type transformer-less connectors and a DB-25 multipin connector, transformerless and balanced.

The analog DB-25 connector is marked “aux output” on the rear panel. This allows the inputs to be split and used in live sound for monitors and front of house (FOH) from an optimized microphone preamp, a very nice feature. All XLR-type connectors are wired 2-pin positive (signal). The output levels of the Aphex 1788 (main and aux) are adjustable from +27 dBu to 0 dBu, with sensitive 1 dB increments.

In use

I first used the Aphex 1788 Eight Channel Mic Preamplifier while doing a recording session with Tony Bennett at The Hit Factory in New York. I used it in a live monitoring situation, which was the first time Tony Bennett was ever recorded this way, with no headphones. Having the microphone (a Sennheiser SKM5000) plugged into the preamplifier with a 20′ cable had an immediate impact sonically on the transients and clarity in the mic’s frequency response. I never heard this mic sound so good cued in headphones or through the speaker system.

Hearing the microphone this way has convinced me of one of the many advantages of the 1788’s ability to be controlled remotely, allowing it to be located near the microphones, providing sonic and operational benefits. Impedance loads affect the performance of microphones and the load impedance of the cable is a direct function of its length.

Some of the common effects of the impedance loading on microphones are the frequency-dependent losses, most noticeable on high frequency and transient response. Using the 1788 unit remotely limits cable length from mic-to-mic preamp, thus reducing these common effects.

On the live show, I used the Model 1788 as a microphone preamp and split and sent it to the FOH and monitor console, showing the flexibility of functions within this unit. Again, there was an impressive difference in the sonic characteristics of the mics split with the Aphex compared to conventional transformer or passive splits I have used with sound companies in the past.

One thing I noticed while using this unit is that it runs fairly warm. The manual specifically recommends 1/2″ of vented airspace around the Aphex 1788, and I would strongly suggest adhering to this recommendation. If using the 1788 outside in warm environments, I strongly recommend rack ventilation fans.

Another nice feature of this unit is its ability to group channels in the multiple channel mode. When it is advantageous to make gain adjustments that will affect an entire group of reeds or trumpets, for example, it can be easily done by making one gain change that affects the whole ensemble.

Another well-thought-out feature is automatic lockout, which prevents making adjustments after 5 minutes of the last command entered, unless the local control button is pushed. This prevents accidental adjustments after making final settings.


The Aphex 1788 Eight Channel Microphone Preamplifier is an extremely well-designed new product with a full range of applications, from sound reinforcement market to studio recording. It has some patent-pending circuits that make this product unique. The 1788’s audio quality, numerous features, ease-of-use and flexibility render it a product worthy of strong consideration if looking for mic preamps to take the quality of your sound package to another level.