ATI HDA600 User Manual

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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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and output jacks. Individual direct inputs can also be configured as BALANCED MONO inputs (HI-LO-SHLD = TRS) by moving internal jumper plugs PX01 to the BAL MONO position and adding a jumper plug at PX02 to combine left and right output channels. PX02 can also mono sum a single output if desired. (X in a part number indicates channel 1 thru 6).

A SIGNAL PRESENT indicator for each output channel indicates at about 30dB below nominal input levels. The HDA600 includes an internal bi-polar power supply that will operate at 115 or 230VAC by changing internal jumpers. The power cord is a standard IEC320 type that you can easily swipe from someone else if you lose it.

CONNECTIONS

Balanced inputs are connected with their HI to XLR pin2 or TRS -TIP and LO to XLR pin3 or TRS-RING, Shields go to XLR pin1 or TRS-SHLD. Unbalanced input lines should be connected with their center hot wire to XLR pin 2 or TRS-TIP and with the cable shield to XLR pin 1 or TRS-SHLD. Be careful to observe HI-LO input polarity to avoid monaural or center stage cancellation effects

The HDA600 is shipped setup for -10dBu nominal Program input level (+12dBu peak). An internal jumper plug P2 may be moved to accommodate levels at +4dBu nominal (+22dBu peak). To change P2, remove the top cover by removing the four upper Phillips head screws (two on each side). P2 is located on the right side of the PC board directly behind the volume control and has two positions; for –10dBu inputs move the plug to the left, for +4dBu inputs move the plug toward the right. Ensure that no internal wiring is caught or pinched, replace the cover and screws.

Use only TRS output plugs and stereo headphones. The use of TS plugs on mono headphones shorts one headphone output to ground. Although this will not damage the HDA400, it will load down the power supply and reduce maximum output levels to the other output channels. Output TRS plugs should all be wired Left to TIP, Right to RING and common to SHIELD.

CAUTION

The HDA600 provides a comfortable listening level of 1mW at around 12 o’clock on the volume control for most headsets. The HDA400 is capable of driving many headsets to DANGEROUS LEVELS over 120dB SPL. If you can hear distortion, it is TOO LOUD! Levels near 120dB SPL can easily cause PERMANENT HEARING DAMAGE.

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PERFORMANCE SPECIFICATIONS

OUTPUTS: Six high compliance 6V/80mA stereo drivers capable of over

100mW into six 32 to 600 ohm stereo headphones

DYNAMIC RANGE: 110dB Typical at output into 600-ohm headphones

DISTORTION: .10% THD max, .01% type, 20-20000 Hz, any level below

clipping

RESPONSE: +0/-.5dB, 20-20000 Hz

GAIN: Program Inputs 26dB.

Cue Input 65db Mic, 35 or 25dB line, Direct Input 10dB.

NOISE: Program Input -90dBu E.I.N., 20 – 20000 Hz Cue Mic Input -

110dBu E.I.N.

Direct Inputs –90dBu E.I.N.

SEPARATION: 70dB minimum at 1kHz

INPUTS: Program: Stereo, 20K balanced, bridging, -10 or +4dBu

nominal Cue: Mono, 2Kohm balanced, diode protected, -50, and -10, 0dBu nom. Direct: Stereo 10K unbalanced or Mono 20K balanced, 0dBu nominal

PHANTOM PWR: +12VDC available for Cue Microphone, selected with P3 and

S2 in MIC position, Resource = 600 ohms

INDICATORS: INPUT CLIP - onset of input stage clipping, Yellow LED CUE CLIP – onset of cue input clipping, Yellow LED

SIGNAL PRESENT– lights 20dB below nominal input level. Six Green LEDs

POWER – monitors internal DC voltage - Red LED

POWER: 115/230VAC +/- 10%, 50/60Hz, 24VA, and IEC320 3 pin

connector

SIZE: 1RU package; 19”(48.3cm) W x 1 ¾”(4.5cm) H x

7.5”(19.05cm) D 15lbs (6Kg)

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ATI HDA600 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual