ATI HDA600 User Manual

HDA600

STEREO HEADPHONE AMPLIFIERS

OPERATING AND MAINTENANCE MANUAL

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DESCRIPTION

The HDA600 is a rugged, AC powered headphone amplifier that will provide excellent performance driving a wide range of typical stereo headphones. It will drive the usual 32 to 600 ohm high efficiency stereo headphones to teeth rattling levels near 120dB SPL with a combination of high output voltage swing (16Vp-p) for high impedance phones and a protected high current capability (.2Ap-p) for low impedance phones. It will do the above at distortion levels below .10% and response flat to .25db both measured over the full frequency range of 20Hz to 20kHz.

The HDA600 provides a stereo program input plus a mono cue input driving six stereo headphone output drivers. The HDA600 will bridge both balanced and unbalanced program input lines with individual left and right XLR and ¼ inch TRS input connectors. The spare connector set may be used to loop-through the input signal to additional HDAs. Inputs are electronically balanced but will operate properly when an unbalanced ¼ inch plug is inserted. An internal input stage gain selector plug (P2) optimizes the input stage gain for either -10dBu or +4dBu nominal inputs or the program INPUT CLIP indicator shows input overdrive. A MASTER LEVEL control and MONO/STEREO switch adjust the program signal fed to all output channels via an internal stereo distribution buss. The MONO/STEREO switch allows a quick check of the mono compatibility of a stereo mix and allows two separate mono signals, applied to the stereo inputs, to be easily summed for monitoring.

A balanced CUE input at either microphone or line level is input through paralleled XLR and TRS connectors. Mic or Line level is selected with rear panel MIC/LINE SWITCH (S2). Line level at –10 or 0dBu is selected with internal jumper plug P4. Phantom power suitable for most electric type microphones (+12VDC) can be selected with internal jumper plug P3 and is switched on only in the MIC mode with the MIC/LINE switch. The CUE signal may be selected into either right, left or both distribution busses with front panel pushbuttons. A CUE LEVEL control and CUE CLIP overdrive indicator are included. The CUE input is ideal to add an IFB or mix-minus feed into the mix in an onair studio application or a click track into one channel in a recording studio or instructor comments in a classroom setting or language laboratory. Six individual output channels bridge the internal stereo distribution buss and drive paralleled front and rear panel ¼ inch TRS output jacks. The high compliance output circuitry comfortably drives all stereo headphones from 32 to 600 ohms. Although designed to drive either front or rear outputs, two sets of headphones can be plugged in to a single channel with reduced drive to each. To avoid major level differences, identical headphones should be used in this case. The rear jacks can also feed remote headphone distribution boxes. Individual output channels can be setup for monaural operation by inserting a jumper plug into the PX02 position. Do not use mono headphones with a Tip – Sleeve plug with the HDA600.

DIRECT inputs into each output channel are available on the rear panel. A TRS plug wired as UNBALANCED STEREO (L-R-GND =TRS) inserted into a direct input will interrupt the main mix and feed its own stereo signal through that channel's amplifier

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