Tape Recording Magazine - AmericanRadioHistory.Com

N
-o
-o
Left: The transformer hookup that
is shown in Figure 2B on the facing
page. The transformer and condensers
can be mounted neatly
next to the volume control in the
radio or TV set as shown. The volume
control is at the bottom of
the picture. Right: The simpler
hookup shown in Figure 2A. This
will work in most cases but hookup
2B may be required in stubborn
cases of hum. The parts may be
obtained from any radio supply
house.
impedance (AC resistance) of 4 to 8 ohms. The mike input
on your recorder will have an impedance of from 10,000
ohms up. If you connect the 8 ohms to the 10,000, your
recording will sound distorted or tinny. You have a great
mismatch. In a case such as this you buy a transformer, one
coil of which has an impedance of 8 ohms and the other
coil 10,000 ohms. You connect the 8 ohm side to your
speaker and the other side to the mike jack. You have now
"matched" the output to the input and whatever goes in one
end should come out the other unchanged.
The best point to make a take -off for recording is generally
at the volume control of an AM FM tuner, radio, TV set
or another recorder. At this point, if properly connected,
each of the prerequisites are met with no noticeable effect on
the volume or quality of the equipment being tapped. (See
Fig. 2A).
Use only high impedance coaxial (single conductor
shielded) microphone cable not exceeding 25 feet in length
connected as shown. Make sure that the shield provides the
ground by connecting it to both chassis. The condenser
value may be increased to a maximum of .1 mfd. if addi-
tional bass response is required by some tape recorders and
the addition of the "R" resistor of 25,000 ohms at the recorder
input may be required to reduce mismatch in some
types of recorders which have one input for both mike and
phono or radio.
When connecting to a crystal phono pickup connect directly
to the crystal output leads being sure to connect the
shield to the frame of the turntable, if possible. If a reluctance
/magnetic type of pickup is used connect to the
pre -amplifier unit with the shield conductor connected to
the pre -amplifier chassis ground.
Figure 2B shows the connection required for audio units
such as an AC DC radio or TV set. These have the "chassis
connected above ground" for Bias purposes and cannot be
connected as shown in Fig. 2A. The "chassis above ground"
means that there is an actual voltage on the chassis itself
instead of being neutral or "grounded."
In some stubborn cases, where a hookup such as is shown
in 2A would normally be adequate, the hookup shown in 2B
must be used instead. The connecting cable should be high
(Continued on page 49)
---
The Cornell- Dubilier AC line filter is shown at right. Into this is
plugged a three -way adapter and all units, radio, TV and recorder
plugged into it for best results. The terminal at the top of the case
is for the ground wire which may be connected to the center screw on
the outlet face plate or other good ground. The line filter will
eliminate clicks and noise coming in over the commercial power wires.
45