ATI Technologies HDA600 Operating instructions

Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax [phone] | www. audio.com
© Copyright 1997-2007, Audio Technologies Incorporated - Printed in USA
HDA600
STEREO HEADPHONE AMPLIFIERS
OPERATING AND MAINTENANCE MANUAL

Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax [phone] | www. audio.com
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 on-
air 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

Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax [phone] | www. audio.com
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.

Audio Technologies Inc. | 154 Cooper Road #902 | West Berlin, NJ 08091 | Voice 856-719-9900 | Fax [phone] | www. audio.com
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)