ATI Technologies PB2X8 Instrucciones de funcionamiento

Audio Technologies Inc.  856-719-9900  sales@atiaudio.com  www.

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PB2X8

DISTRIBUTION AMPLIFIER

OPERATING AND MAINTENANCE MANUAL

Audio Technologies Inc.  856-719-9900  sales@atiaudio.com  www.

audio.com

DESCRIPTION

The PB2X8 is an analog audio distribution amplifier with special features making

it ideal for a Press Distribution system. It provides two high quality XLR inputs

that can be individually switched or mixed into any of eight isolated line level

outputs. Each input may be individually switched for microphone or line level

operation with phantom power and low cut filters available for the microphone

inputs.

A calibrated test tone oscillator can be switched in place of either input for

system test and level checks.

A bargraph LED display meters either input, or any of the eight outputs. The

meter may be switched for OVU indication at nominal XLR line outputs of +4, +8

or +18dBm with the top position an effective headroom indicator. A headphone

output follows the meter selection for audible monitoring.

Each of the eight XLR outputs is a separate, independent and isolated amplifier

channel which may be switched to the A input, the B input or to the A+B sum to

mix both inputs. Each output channel has its own level control and a transformer

isolated XLR output, which will drive balanced or unbalanced 600 ohm and

higher loads at full line level. In addition, alternate output positions provide either

a 1/4-inch or a 3.5mm TRS jack with an attenuated output at -10dBu IHF level.

Internal jumper plugs can convert any of the –10 outputs to a nominal

microphone level at –50dBu. Either balanced TRS (Tip/Ring/Sleeve) plugs or

unbalanced TS (Tip/Sleeve) plugs may be interchangeably plugged into the

PB2X8.

A pair of 1/4-inch TRS jacks parallels the main XLR inputs to allow convenient

loop-thru connection into another PB2X8 for further system expansion. A ground

lift switch isolates the shields of the loop-thru TRS jacks to prevent ground loop

induced hum.

PURPOSE

Use your PB2X8 to clear out the usual forest of podium microphones by

distributing just an unobtrusive single or back-up pair of microphones.

Safely Isolate and distribute audio to all types of professional, semi-professional

and consumer grade recorders with no interaction or hum loops.

Easily match multiple level requirements and connector types.

Cleanly mix or switch both inputs into any or all eight outputs.

Audio Technologies Inc.  856-719-9900  sales@atiaudio.com  www.

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Efficiently distribute stereo, left, right and summed mono audio from a single

stereo microphone, IHF or 600 ohm line level source.

CIRCUIT OPERATION

Input signals applied to the rear panel XLR or TRS jacks are RF filtered by a

ferrite balun and capacitor network and limited by zener clippers. Low noise

balanced input instrumentation amplifier ICs A1 and A2 are individually switched

to boost microphone inputs by 40dB (MIC position) or provide unity input gain for

line level inputs (LINE position). A second MIC low-cut position on the two input

switches inserts a two pole active 150Hz low cut filter, A3 and A4, into the

microphone signal path to block wind noise and reduce room reverberation.

Input levels A and B are adjusted by pots R13 and R14, boosted l9dB by A3A

and A4A, high pass filtered, fed to the A and B distribution busses by A3B and

A4B and metered by positions A and B on the meter selector. Nominal A and B

input levels should be maintained around OVU on the +4 meter scale.

A 750Hz sine wave test tone oscillator, A5A and A5B, can be switched (via S5)

into either A or B input path just after the input level controls. The test tone

provides a nominal OVU +4 A or B internal buss level to the system. Turn down

the input pots when feeding test tone thru the system, set your XLR line output

levels using the internal meter (1 to 8), OVU LEVEL (+4 or +8) meter switch and

the individual screwdriver output level adjustments, then turn off the test tone and

turn up your input to match your nominal A or B input buss level to the test tone

OVU.

Each of the eight output channels may be driven from either the A input, the B

input or the A+B sum of both inputs. The summing switches are S6 thru S13

driving eight unity gain summing amplifiers (A6A-D and A7A-D) and the output

level pots M45...R87).

Eight 21dB gain output stages (A8 through A15) drive the eight output isolation

transformers (T1 through T8). RC networks across each output transformer

maintain smooth peak free high frequency response even if the line output is not

loaded. The transformers drive the XLR 600 ohm line outputs directly and also

feed their associated 1/4" or 3.5mm TRS output jacks thru resistive balanced

attenuator networks. Jumper plugs P1 through P8, located just inside the rear

panel and accessible by removing the top cover, convert any TRS output from a -

10dBu IHF level to –50dBu microphone level. Tip/Sleeve plugs for unbalanced

loads may be inserted into the TRS jacks with no ill effects on balanced or

unbalanced line level outputs. Shield pin 1 of the XLR output connectors is

ungrounded to avoid hum loops. If necessary, ground jumpers may be inserted

into the PC board directly behind the #1 pin of the output XLR connectors.

Audio Technologies Inc.  856-719-9900  sales@atiaudio.com  www.

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The meter circuit, A16, drives the ten-segment bargraph display with a very close

approximation of VU ballistics. The OVU LEVEL switch, S14, sets the meter OVU

point to +4, +8 or +18dBm equivalent output. The meter CAL trimpot is R176.

Headphone amplifier A17 drives both sides of a stereo headset with an in-phase

signal from the mono input or output channel selected by the rotary meter select

switch. Internal trimpot R186 sets the headphone level. If necessary, readjust

R186 for a comfortable listening level at OVU. Use stereo headphones only;

mono phones short one output.

A5C and A5D form a 40kHz oscillator and voltage doubler to generate the

+48VDC microphone phantom power. Phantom power is applied to both HI and

LO input lines thru matched 6810-ohm resistors only when the input channel is

set for microphone operation and only if the rear panel phantom power switch

(S2) is ON. Regulated + and –15VDC power is provided by IC regulators A18

and A19. A separate +10VDC unregulated supply drives the LED bargraph meter

display. PC board jumpers W1 and W2 set the nominal AC input voltage to

117Vrms. Removing W1 and W2 and inserting W3 sets the input for 234VAC. A

1/2A fuse is required for 117V operation and a 1/4A fuse for 234V.

INSTALLATION

Open the Press Box and adjust output jumper plugs before mounting the unit

under other equipment in your system.

The 1/4" and 3.5mm TRS output jacks are shipped set for -10 dBu (.25V) output

level. If you would like to dedicate some or all of them to -50dBu (2.5mV)

microphone levels, remove the top cover (4 #6 side screws, 2 #4 top screws) and

move the selected jumper plugs (Pl-M). Mark the rear label!

Plug a stereo headphone into the front panel jack and run the test tone oscillator

to check headphone loudness. Adjust PHONES trimpot R186 if necessary.

The PB2X8 Press Box may be desk mounted on its suction cup mounting feet or

EIA rack mounted in 1.75inches using optional heavy-duty rack mounting

brackets P/N 21181-501. Remove the four #6 screws from each side to attach

the optional rack mount brackets.

If you are looping inputs thru to another PB2X8 place the rear panel loop shields

switch in the LIFT position on the sending unit only. This will prevent ground loop

hum via the AC line green wire ground. If you use a TRS loop in jack as your

main (or loop) input, be sure the shield switch is in the GND position. The XLR

input jack’s pin 1 (shield) is permanently grounded.

The wiring convention used on the PB2X8 XLR connectors is pin 2 HI, pin 3 LO,

pin 1 shield. TRS connectors, Tip HI, Ring LO, Sleeve is shield.

Audio Technologies Inc.  856-719-9900  sales@atiaudio.com  www.

audio.com

SPECIFICATIONS

Output Levels XLR: +4dBm nominal, +22dBm max

TRS: -10dBu (.25V), balanced or unbalanced,

-50dBu via internal jumper plug

Input Levels Microphone: -50dBm nominal from 50 to 600

ohm microphone

Line: -10 to +4dBm nominal

Distortion: 0.1% maximum THD, 20 Hz to 20 KHz

+20dBm level

Response: +0, -.25dB, 30Hz to 20kHz

Noise Mic. Inputs -124dBm EIN

20KHZ Bandwidth Line Inputs: -94dBm EIN

MIC Filters: Two pole active low cut, 150Hz

Phantom MIC Power: +48VDC, rear panel switch

Headphone Output: .2W into 600-ohm stereo TRS phones

Test Oscillator: 750Hz at internal buss levels equivalent to

nominal levels

Connectors: XLR type, 1/4inch TRS, 3.5mm TRS

Size: in. (mm) 17(432) W x 1.75(44.5) H x

10.5(267) D

Shipping Weight: 15lbs (6kg)

Mounting: Suction feet for non-slip desk mounting,

optional Rack Mounting Kit 21181-501

Power: 117/234VAC +/-10%, 47 - 63 Hz, 10VA

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