Ferrograph 704 Owners Manual

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CONTENTS

Foreword ,.

General Specification
General Description
OPERATING INSTRUCTIONS

Connections

Power Supply . .

Inputs - Microphone
Tuner (radio)
Pick-up Cartridge
Other Sources t.

Outputs - Loudspeaker
Amplifier..
Tape Recorders
Headphones

Deck Operation .

Tape Loading

Tape Speed

Play

Record H

Automatic and Foil Stop
Fast Wind ,

Replay
Bass and Treble Controls

Output Switch . .
Meter Switch

Record .
Interjection
Stereo Models ..
Radio . . . .
Gramophone
Microphone .. .. ..
Characteristics . .
Placement .
Use of Microphone
Monitoring .. . .

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On a radio without a special output. the best method is to use it
virtually as a tuner and to take the signal from immediately after the
detector stage. usually across the volume control. as this avoids any
hum and distortion associated with the radio output stage. A more
convenient method (though not as good) is to connect to the extension
loudspeaker socket (twisted flex leads can be used). If the radios
internal loudspeaker is disconnected on plugging in, it is normally
necessary to connect a resistor (usually 3 9) across the leads to maintain
the correct load on the radio output stage. If one of the leads is earthed
on the radio, this must be connected to earth at the recorder (to the
longer connection blade on the jack plug).

Nate:-Great care must be taken when connecting to a radio which
will operate from both AC. and DC. power supplies as the chassis
will probably be connected directly to the mains. In this case either a
transformer or isolating capacitors will be required in the signal leads
and it is advisable to consult the manufacturer (or supplier) of the
radio before attempting to connect to other equipment. This does not
apply to a portable radio operating on its own internal batteries.

Pick-up Cartridge

Ceramic and crystal pick-ups can be fed directly into the Line input
as this is high impedance (2M0) and is capable of accepting large
signals (up to 10V). if a crystal pick-up with a very high output is used,
such that the Line gain control is operating over a very small part of its
control range, the output can be reduced as described in the Technical
Section, page 46.

With magnetic pick-ups. some form of correction is necessary to
produce a level response from their velocity characteristic output, and
usually a small preamplifier is used. The circuit of a suitable pre-
amplier, powered from the Auxiliary Socket or a 48V. DC. supply.
is available on request.

For record players, radiograms, etc., having their own pre~amp|ifiers.
these should be used and connected as for a tuner/radio above.

Other Sources

When the signal is obtained from a source not mentioned above. the
correct connection will depend on the signal strength and impedance.
Normally most signals may be fed to the Line input (50mV-10V), but
weak signals should be fed to the Microphone input (SOOuV-15mV).
In cases where there is some doubt, the dealer or relevant manufacturer
should be consulted.

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LOUDSPEAKER LOW LEVEL
MAINS OUTPUT oureurr

INPUT M'AINS
PLUG FUSE

T

c.0090

T
t AUXILIARY 1 LINE
"-- SOCKET" DrC, FUSE INPUT

SELECTOR SELECTOR OUTPUT

FIG. 3. REAR PANEL-MONO

Outputs
Loudspeaker

The Loudspeaker output will provide up to 10 Watts undistorted
output into a 15 or 8 I2 external loudspeaker for high fidelity listening.
Plugging into this socket automatically disconnects the internal
loudspeaker and the external loudspeaker signal is then governed by
the Output, Bass and Treble controls.

Nata-As with other transformerless power output stages, care
should be taken not to short the speaker leads to each other. as this will
probably overload the amplifier and blow the DAC. fuse The faulty
connection must be corrected and the fuse replaced before the amplifier
will function again On the stereo models, there are two fuses - one
for each channel - so that only one channel will be inoperative when a
fuse blowsr However, the oscillator is powered through the Upper
track fuse and should this blow. it will not be possible to record (even
on the Lower track) until the Upper track 00 fuse is replaced, 0n no
account should anti-surge or delay fuses be used

Amplifier

If it is required to use an external amplifier and loudspeaker. either
instead of or together with the internal amplifier and loudspeakers. it
may be fed from the 600 fl output. This is an emitter follower giving
approximately 2V signal at 60012 impedance from a full depth recording,
and while the impedance into which it is fed is not critical. impedances
of less than 600$! will reduce the output available. If the internal
loudspeakers are not required the Output control can be turned to
zero as the 600i! output is independent of the Output, Bass and
Treble controls

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