ATI Technologies DA416 Manuale operativo e di manutenzione - Pagina 2

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ATI Technologies DA416 Manuale operativo e di manutenzione

DESCRIPTION

Your DA208/416 provides two (DA208) or four (DA416) independent one in by

four out circuit groups. A four way feed is sufficient for many applications,

however, if you need more outputs, you can parallel channels by bridging several

inputs across the same line for 1 x 8, 2 x 8 or 1 x 16 operation. Since each input

circuit has 30k ohm balanced input impedance, you can simply terminate your

source line with a single 620-ohm resistor (if necessary) and then parallel as

many inputs as necessary across it.

Each input can bridge line levels up to +24dBm without clipping. Common mode

hum signals are attenuated by 70dB and the input resistor network is split and

heavily bypassed for good protection from RF signals riding on the input lines.

The input differential amplifier operates at slightly less than unity gain to optimize

input headroom and to prevent any signal clipping from occurring prior to the gain

controls.

Each output consists of an adjustable gain stage driving the HI output terminal

along with a unity gain inverter stage. The inverter drives the LO output in

opposite phase to provide an active balanced output. The adjustable gain stage

utilizes a unique circuit arrangement that allows us to provide a smooth, full

range logarithmic gain control for each output using a linear cermet

potentiometer. This circuit provides 20dB gain at full clockwise rotation, unity gain

in the 12 o'clock position and tapers smoothly to full off at the full CCW position.

Since we actually vary the gain of the output stage rather than taking the more

conventional approach of adjusting the input level to a fixed gain stage, we can

use the DA at low output levels with very little noise penalty. You can easily

match the DA outputs to console medium level inputs (-20dBm) or to drive semi

pro RCA inputs (single ended at. 10Vrms) without requiring outboard attenuator

pads.

Each balanced output stage is isolated from the output terminals by DC blocking

capacitors and 400 ohms of build out resistance. The build out resistors are split

and bypassed to prevent any RF signals that might be picked up on a output line

from feeding back into the DA.

Your DA has clipping indicators to warn you of overdriven and overloaded

outputs. These indicators individually sense nonlinear operation of any output

channel by measuring the error voltage at the feedback terminal of the HI side

output amplifier. As long as the output stage operates linearly, the error voltage

at it's negative input (for example WA pin 9) will remain very small. The onset of

clipping, current limiting or even slew rate limiting immediately causes a large

increase in this error signal, which is then fed through R25 to the error amplifier

U5A at pin 13. U5A, in turn, drives the clipping LED through Q1. Feedback

voltages also feed the error amplifier from three other output channels.

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