GSXH2 HEADPHONE LIMITER

This unit has been developed in conjunction with the Capital Radio group to provide a new way of controlling headphone levels.  The aim is to enable the user to achieve adequately high listening levels without hearing damage.
Hearing damage is caused by noise exposure. This means it is safe to listen at a higher level for a short period or a lower level for a long period. Typical possibilities of reaching the maximum permitted exposure are as follows:

A full 8 hours at 85dB(A)
1 hour at 94dB(A) and 7 hours at 75dB(A)
12 mins at 100dB(A) plus 48 mins at 85dB(A) plus 7 hours at 75dB(A)

    GSXH2 Front.jpg (73026 bytes) GSXH2 rear.jpg (72625 bytes)
FRONT & REAR VIEWS OF GSXH2

The Glensound GSXH2 & GS1U-044 are headphone limiter units that enable higher levels of audio to be used for short periods in a controlled way.  They are stereo, mains powered active units, the GSXH2 being designed to mount under a desk and containing 1 stereo headphone limiter and the GS1U-044 being a 1U subrack containing 2 separate stereo headphone limiters.

Both units contain a compressor with a large compression ratio controlled by side chains that contain ‘A’ weighting filters and special rectifiers.  This effectively limits the maximum voltage level.  In addition to the compressors there are also circuits designed to monitor the level to the headphones.

In its normal usage the compressors will keep the noise levels below critical.  However a key type switch is provided that allows the user to increase the maximum level. Information that this switch is operated is available on the rear panel D connector, thus allowing ‘management’ to log and control the correct usage of the limiters.

Different makes & types of headphones have different sensitivity levels, therefore the GSXH2 & GS1U-044 need to be calibrated for individual types of headphones. To ensure that the correct output audio levels are emitted depending on the headphone type connected a calibration resistor (of a specific value for a specific type of headphones) is used mounted in a 5 pin XLR connector used as the headphones connector. Click here for an up to date list of headphones that the unit has been calibrated for use with.

The maximum output levels that the limiters allow the headphones to emit are +85dB(A) with the user operated key switch turned off or +90dB(A) with this keyswitch in the ‘on’ position. If a loop is made on the units rear panel D connector then these levels both increase by 5dB.

As an indication for the user, of the audio level to the headphones yellow & red large LEDs are provided on the front panels of the units. ‘Open collector’ outputs are also provided on the rear panel D connector for external indication of this level. Without the ‘D’ connectors loop made the yellow LED indicates a level of 85dB(A) and the red LED indicates a level of 90dB(A), with the loop made and the key switch in the on position then the yellow LED indicates a level of 90dB(A) and the red LED indicates a level of 95dB(A).

Headphone connections, remote key switch operation, the loop to increase overall levels, remote LED indication and increased level selected information is all available on a rear panel 15 way ‘D’ connector.

The limiters are designed to work with input levels between –20dB & 0dB.

 For further information regarding noise exposure see www.tonywoolf.co.uk

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