ETS HPDA-3 Instructions

The HPDA-3 is a flush wall mounted, headphone monitoring station for use with ETS SM1 series
microphones. The HPDA-3 is housed in a double gang stainless steel plate for ease of installation
on electrical boxes. The HPDA-3 features independent amplifiers and volume controls for up to 3
headphones. The HPDA-3 also features DVR connectivity for live and playback sound
monitoring.

SM1 Microphone Placement

Do not mount the microphone near air conditioning vents, light fixtures or electrical equipment.
The SM1 should be placed as close as possible to the subject(s) to be monitored. The SM1 is
useable at distances of up to 25 feet but is dependent on the level of background noise in the
area. Experimentation in the environment will determine what distances work best.

Cable Run

Run a 22 gauge, stranded, two conductor shielded cable between the SM1 microphone and the
HPDA-3. Keep the cable run distance under 1,000 feet and away from AC power sources, light
fixtures and electrical equipment. Connect power to the + terminal, the audio signal to the "audio"
terminal and ground to the – terminal. The Ground of the power and audio signal must share a
common ground for proper operation. See Figure 1 for connection diagram.

Mounting

The HPDA-3 can be flush mounted in a wall or surface mounted. We suggest you use a remodel
box for sheet rock installations.

Adjusting the SM1 Gain

We suggest setting the gain on the SM1 microphone full clockwise and if needed make any
further mic gain adjustments with the "Mic Level" control on the HPDA-3.

Setting the SM1 Hi-Cut/Lo-Cut Jumpers

The normal frequency response of the SM1 microphone is 500-13Khz. When both switched "in",
The "HI Cut" and "Lo Cut" filters set the SM1's frequency response to 900-6Khz. Enabling one or
both of the filters is useful when background noise needs to be further reduced and intelligibility of
speech emphasized. We recommend experimenting with the switch settings to achieve the best
result for your application.

Headphones

You can plug any type of headphones into these jacks and adjust the volume with the
corresponding volume control.

DVR or audio recorder connection

The HPDA-3 can be connected to a DVR as shown in figure 1. The switch on the front of the
HPDA-3 is used to set the source to live audio or DVR playback audio. If a recorder is not used,
place the switch in the live (right) position. For playback, place the switch in the left position. If a
recorder is not used, the microphone will not be heard in the "playback" position of the switch.
HPDA-3 Monitoring Station
Instructions