Fairchild 610 Instruction Manual

FAIRCHILD MODEL 610 10 WATT AMPLIFIER

GENERAL

The FAIRCHILD MODEL 610 amplifier is a fully siliconized, 10

watt rms monitor amplifier with short circuit and overload

protection. The amplifier features compact design, low dis-
tortion, flat response and low noise. It has bridging input,
transformerless output and an integrated power supply.

The complete amplifier, less line transformer, is on printed
circuit card. In this design, heat sink of the output stage
is coupled to the chassis of the amplifier, effectively in-
creasing heat radiating surface.

The MODEL 610 accommodates input levels from -10 dbm (.25V
bridging) and higher. Minimum level of .25V is required to

produce 10 watts rms power into an 8 ohm load, or 61/2 watts

power into a 16 ohm load.
The amplifier circuit consists of four directly coupled stages

of amplification, phase inversion and driving. DC feedback
loops stabilize the operating point over a wide range of oper-

ating temperatures with no degradation in performance of the
unit.

Instantaneous overload protection is obtained through current-
limiting transistors in the driving circuit of each half of the

output stage. As current through either of the output transis-
tors exceeds preset value (clipping point for 10 watts), output

stage is clamped down driving the output stage into non-conductive

state. Output stage is CTASS AB circuit, with maximum current
flowing through the transistors being .4 amps, and idling current

20 ma.

APPLICATIONS
The MODEL 610 amplifier is intended for professional use in systems

where moderate power levels are adequate. It is excellent for driv-

ing speakers with or without transformer isolation. 70 volt line

can be achieved b using appropriate step-up transformer with 1:8

ratio, primary being 4 or 8 ohms. The 610 can be used in cue

circuits, talkback and intercom systems where high quality and

high reliability are required. If the unit is used as a line

amplifier, a transformer may be used with sufficiently high power

rating and low distortion so that full use of available power can

be achieved.

INSTALLATION & OPERATION

- MODEL 610

The MODEL 610 amplifier may be rack mounted. A rack mounting
frame (MODEL 662RM) is available for this purpose. Five 610s

can be placed side-by-side in this frame, taking up 51/4" of
rack space. If less than five amplifiers are mounted in the
frame, either blank panels can be used to fill in or other
FAIRCHILD INTEGRA components can be mounted in the empty space.
CAUTION, however, must be exercised not to mount equipment with

mic transformers next to the amplifiers. The integral power

supply of the amplifier creates

AC

field capable of inducing

60 cycle hum into low level transformers.

ALTHOUGH the chassis of the 610 amplfier is made out of steel

for shielding purposes, it is recommended that the amplifier

be checked out for proximity interference before being mounted

next to other amplifiers.

The 610 will work off any impedance not exceeding 10,000 ohms,
and levels not lower than -10dbm (.25V). It has capacitive

input isolation. In order to run it off a balanced line, an

input transformer may be in order. However, direct operation
of the 610 from a balanced line is feasible provided that the
amplifier ground is a floating ground and the load is not
grounded (either transformer output or speaker).

CONNECTICNS

Input to the amplifier is

TERMINALS 1

and 2 -

TERMINAL 2

being

ground. Output of the amplifier is TERMINALS 3 and 4 - TERMINAL

4 being low side.

Care should be exercised in making appropriate grounding to the

load for if input and output grounds are interconnected to the

same terminal output, current could flow thioush the input
ground causing an unwanted feedback condition.

SHIELDS

If shielded wire is used for the input, shield can be tied to

either the case ground of the rack assembly, or to the low side
of the input, providing the other end of the shield is not tied
to ground and isfloating. Shield should be tied at one end only,
and it may be at the source end. Internal shielding of the
amplifier is tied to the chassis ground internally, and is auto-
matically grounded when the unit is mounted on the grounded rack.

PRECAUTIONS

The YODEL 610 amplifier is capable of taking abuse. However,

some operating precautions should be exercised. As stated in
the specifications, input level of -10 dbm will produce full
output into any load. Since the outut impedance is very low,
varying loads will not change the output level to any appreciable
degree. Short circuiting output will produce instantaneous turn
off of the output transistors. It is vfxtually impossible