Leak stereo 30 owners manual

Page 1

STEREO 30 PLUS
INTEGRATED TRANSISTORISEO
AMPLIFIER

INSTALLATION ' OPERATION ° MAINTENANCE

IMPORTANT

Do not connect any ACIDC device (TV. Tape or Radio) to the Stereo 30 Plus amplifier. These devices
may have high AC potentials on their chassis capable of causmg serious damage to the Stereo 30 Plus
amplifier.

INSTALLING THE STEREO SO RLUS

IQ

JI

(i.

If you have bought the 'Stereo 30 Plus already installed in the standard LEAK decorative wood case
the mounting of the amplifier is completed.

If you have bought the Stereo 3() Plus in chassis form it may be mounted in a LEAK tunerramplifier
wood case or on a panel of any thickness. through a cut-out of L? ,90 3:3" (3| .8 x l0 cms.). To mount
on a panel: pass the body of the amplifier through the cut-out until the front plate butts against the panel.
then pass the U-shaped bracket over the back of the amplifier and fix it by passing the wing screw
through the hole in the bracket and into the threaded hank-bush in the centre of the rear panel on the
amplifier. Tighten the wing screw just enough to prevent the front plate of the amplifier from slipping
on the panel.

The mains transformer primary is wound for voltages of 110. 7. I30. 2l0, 230. 250 (40-60 Hz). The

circular voltage selector (marked VOLTSon the back of the amplifier) should be withdrawn to its
fullest extent. rotated so that the arrow indicates the voltage nearest to your supply and then reinserted.

The amplifier is fitted with a l3-ft. (4-metre) power cable. either 2-core or 3-core according to the prac-
tice of the country to which it is shipped. This cable should be connected to the domestic power
supply as follows 2» -

((I' 3-core cable. If the power supply socket has a third (earth) contact. the green/yellow wire should

be connected to the corresponding pin on the power supply plug. The red or brown wire should
be connected to the live pin (usually marked L) and the black or blue wire should be connected
to the neutral pin (usually marked N').
If the socket has only two contacts then connect the red and black or brown and blue wires to
the pins of the plug fitting this socket. Cut off the green/yellow lead and run a separate earth
(ground) lead from the 'EARTH terminal on the rear of the chassis to the water system or to
the steel conduit encasing the house wiring. provided that these systems themselves are properly
grounded.

(b) 2-core cable. The plug fitted to the power cable should be connected to the domestic power
supply socket. A separate earth (ground) lead should be run from the EARTH terminal on the
rear of the Chassis to the water system or to the steel conduit encasing the house wiring. provided
that these systems themselves are properly grounded.

It is bad practice to omit this earth connection, and to ensure freedom from hum (caused by
earth loops) no other earth connection should be made.
The amplifier is switched on by pressing the button marked POWER ONIOFF.

Double sockets marked AC OUTLETS are fitted as a convenient source of power supply for turn-
tables. radio tuners or tape recorders. The power taken from these sockets should be limited to 100
watts or thereabouts. These sockets are not fused but are controlled by the amplifier switch.

The amplifier has been designed to operate under domestic conditions for the reproduction of speech
and music anywhere in the world. Due to the very small amount of heat generated by the amplifier it
is possible to mount the chassis model of the amplifier in a small cabinet and it is only necessary to
ensure that the ventilating slots in the cover plates are unobstructed. Sinewave testing at full power
output should be of short duration. particularly at high frequencies. otherwise overheating may occur

and the l.6A DC fuse may blow.

Fusing. In addition to the normal AC fuse and in order to give the amplifier maximum protection
against abuse we have fitted a quick acting 1.6A DC fuse. Care should be taken to avoid shorting the
loudspeaker leads as this may blow the fuse. but in order to cover this contingency we have supplied
spare fuses which are fitted in the clips on the rear panel of the amplifier adjacent to the fuseholders.

Loudspeakers of any impedance from 4-l5 ohms may be used and they should be connected to the plugs
fitting the pair of sockets marked LOUDSPEAKERS 4-15 OHMS R and L.

Page 2

It will be seen from the circuit diagram that one side of the loudspeaker wiring is connected to the
chassis, and no other part of the loudspeaker wiring should be earthed elsewhere.

If you wish to use a loudspeaker which has a built-in matching transformer (e.g. a full range electro-
static loudspeaker) it may be necessary to connect 2 ohm 2 watt resistors in series with one of the two
leads connecting each loudspeaker to the Stereo 30 Plus amplifier. Failure to connect these resistors
may result in a form of low frequency instability depending on the characteristics of the matching trans-
former in the loudspeaker.

Phasing. It is vitally important that the diaphragms of your two loudspeakers move in phase. i.e. in
the same direction at the same instant. To make sure of this note very carefully the following :--
First your loudspeaker cable must be colour coded. e.g. red and black. If you are using identical loud-
speakers (as you certainly should if you want true stereo) the manufacturer will doubtless have kept to
a convention when marking the terminals, very often simply red and black. In this case the loud-
speakers will be in phase when connected as shown below.

A RED wme-

- 0 RED
L :K LOUDSPEAKER L
BLACK WIRE

LOUDSPEAKERS A? 0 BLACK
4-15 OHMS RED WIRE RED

C>
R / LOUDSPEAKER 12'

(Gig QEACKWIRE EBIACK

If your loudspeaker terminals are unmarked or you are using dissimilar loudspeakers you can check
the phase as follows: place the two loudspeakers as close together as possible; depress the button
marked INPUT R and set the input switch to PICKUP 1. Connect an unscreened length of wire
(about 1ft.) to the PICKUP 1 R socket. Turn BASS control to maximum and then turn up VOLUME
control until the hum picked up by the unscreened lead is fairly loud. Then reverse the leads to one
loudspeaker; the condition which gives you noticeably more bass hum is the correct connection, i.e. the
loudspeakers are in phase.

PHONES. A 3-contact jack socket is provided on the front panel to enable the user to connect a pair
of stereo headphones for personal listening when it is not desired to use a pair of loudspeakers.

The Stereo 30 Plus is despatched from the factory with a dummy plug inserted in this jack socket to
balance the panel layout and improve the appearance of the amplifier. If you wish to use headphones
then pull out the dummy plug and insert the headphone jack plug.

We have wired this 3-contact jack socket to conform to the usual practice adopted by headphone
manufacturers. i.e., the left channel output is connected to the tip, the right channel output is connected
to the ring and the common connection to both channels is connected to the sleeve.

If the headphones you possess are not terminated in a 3-contact jack plug then a plug of this type
should be obtained from your radio dealer and connected as shown below :-~

SLEEV r TERMINAL

COMMON WIRE '/ '

-. [D

H
RIGHT'CHANNEL l socomcr

9 P
HEADPHONES me Tritium JACK LUG
LerrcHANNEL . ,
was me TERMINAL

If your stereo headphones are supplied with a four wire output lead. one lead from the right head-
piece and one lead from the left headpiece should be joined and connected to the sleeve termination.
The correct phasing of the signals from your stereo headphones is very important and in all probability
the manufacture of the headphones will have indicated which leads should be joined together and taken
to the sleeve termination. Should this information not be available then proceed as in paragraph 8
above-reversing the connections to one headpiece when the condition which gives noticeably more
bass hum will be correct.

Two 100 ohm resistors (R56L and R56R) are wired in series with the L and R headphone connec-
tions to enable most headphones to be directly connected to the socket. If. however. the headphones
that you are using do not give satisfactory results it may be necessary to connect another resistor across
each headphone. or to alter the value of the resistors that have been fitted inside the Stereo 30 Plus
amplifier. This is because the impedance and sensitivity of headphones varies considerably between
the manufacturers.