ART HPFX Headphone Monitor System with Digital Effects

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A.R.T. HPFX Headphone Amp


The HPFX is Applied Research and Technology's stand-alone stereo headphone mixer/amplifier with microphone preamplifiers and built-in digital effects. It allows singers and instrumentalists to control the volume, mix and effects fed into their headphones without altering the master console' s mix or another player's monitor mix.


Ease of Use: 4
Value: 5
Functionality: 4

Your Own Mix

With most headphone mixer/amplifiers the overall volume of each headset is the only variable a performer can adjust to personal taste. The engineer and/or producer builds the best headphone mix possible for the performing players. Newly recorded tracks are mixed in with other backing tracks and sent back to the headphones. With HPFX, each musician is given more extensive and independent control over his or her headphone mix. The HPFX is a half-rackspace unit powered by the included wall-wart power supply.

Overcoming Latency

The HPFX expands the possibilities for headphone monitoring and also solves a problem common to computer-based recording. First of all, the HPFX takes care of the singer or musician who wants to control not only the volume but also the relationship (mix) between themselves and the backing track. ART takes this even one step further by providing the ability to add a digital effect to the player's sound--an effect that does not get recorded. Second, the HPFX lets the performer's voice or instrument be heard "live,"directly from the microphone he/she is using. This works around the latency inherent in newer (and especially lower-cost) digital computer hard-disk recording systems. Some degree of latency occurs in all computer audio systems because it takes time for the system (the computer's soundcard and software) to convert incoming analog signals to digital, process them, record to the hard drive and then convert them back to analog signals so that we humans can hear and then play along. Needless to say, excessive latency in the monitoring of a performance makes recording untenable.

Built-in Mic Preamps in a Headphone Mixer?

The HPFX has two microphone preamps that "pick off" the microphone's signal from XLR microphone input connectors on the unit's back panel. The microphone is plugged directly into the HPFX and then its signal is passed on to the engineer's recording console microphone input through the HPFX's XLR mic output connector. The front panel has a mix level control for each microphone that goes directly into the HPFX's headphone mix. These level controls do not affect the recording level or the sound the engineer is getting. It should be noted here that this is the raw mic sound, without benefit of any processing that the engineer might add when recording, like equalization or compression. In addition to level, the front panel also has a separate digital effect level for each microphone used. Finally, there is rear-panel jack called Effects Output that provides just the preamplified microphone signals with or without effects added from the HPFX. This is for recording the HPFX's output, if you should so choose, to your computer's soundcard.

16 Built-In Digital Effects

There are 16 digital effects available to the microphone signal: four slapback delays; four echo effects; five reverb settings; and three special effects such as a flanger or chorus. ART says in the manual that the effects are tailored for vocals but I found them to sound good on guitars as well. These stereo and dual digital effects use 24-bit DSP and 20-bit D/A and A/D converters. There is a rotary Digital F/X selector on the front panel which runs through all 16 effects in a proper and logical order (e.g., the reverbs start short and go on to longer settings). Once you have selected something you like, you can adjust the main parameter to your taste with the Parameter Adjust control. There is also a main bypass switch that mutes the effect quickly.

There are four separate headphone output positions on the HPFX. Each output has its own level, jack and amplifier so there is no concern that the sound will change when more than one person plugs in. Another advantage of separate volume controls and amps is that different kinds of headphones can be used at each input. There are line-level input jacks (left and right) on the back panel for feeding a stereo backing track mix from the recording console or computer. The initial level of this signal is controlled by the recording engineer but the individual headphone volume controls give you up to 18dB of additional gain if you need it.

In The Studio

I gave the HPFX a trial run in the studio at a tracking session where I needed a second headphone system. The drummer wanted his phones loud with a very hot metronome click track. The rest of the band couldn't work with that mix so I used the HPFX to give them my control-room mix. As the session progressed, everyone using the HPFX wanted more bass guitar than I wanted to hear in the control room (probably due to the volume of the drummer in the room or just the lack of solid low end in the cheap headphones themselves). I took a tap from the bass player's direct box and plugged it into the HPFX. Since I was recording analog 24-track (no computers), there wasn't any latency issue between the live bass signal and the bass signal in the control-room mix I was already sending to the HPFX. It also worked out that the two bass signals were in phase. The musicians could add more bass easily with the mic level control on the HPFX's front panel.

A good headphone system like the HPFX makes a fine addition to any home or project studio. This unit handily solves some of the problems that have come with modern recording techniques, too, making the process simpler and more flexible for the performer (you) and the recording engineer (also you).

The HPFX carries a three-year warranty and sells for $299 MSRP. Applied Research & Technology at 215 Tremont St., Rochester, NY 14608. Telephone: 716-436-2720 or Fax: 716-436-3942. Web to:

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