Quad 520 Owners Manual

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Quad 520 Owners Manual

Extracted text from Quad 520 Owners Manual (Ocr-read)

Page 1

QUQD 520

Twin Channel

instruction book

Page 2

QURD 52C instruction book

The Quad 520 is a two channel power amplifier deSigned for Broadcast. Recording and other applications in the
audio industry. providing 100 watts per channel into 8 ohms and 150 watts per channel into 4 ohms.

The Quad 520 uses a development of the Current Dumping (feed lonivard error correction) circuit technique. a Quad
invention first used in the Quad 405 and for which Quad was granted a Queen's Award for Technological Innovation.
Current dumping eliminates many of the problems associated with transistor amplifiers. and is covered by patents in
several countries. In a current dumping amplifier there is in effect both a low powered very high quality amplifier and
a high powered heavy duty amplifier. The low power amplifier controls the loudspeakers at all times. calling upon the
high power section to provide most of the muscle. The small amplifier is so arranged - it carries an error signal -
that provided the larger power transistors (the dumpers) get within the target area of the required output current it
will fill in the remainder accurately and completely. The reproduced quality is solely dependent on the small amplifier
which because of its low power can be made very good indeed.

Problems of crossover. crossover distortion. quiescent current adjustment. thermal tracking, transistor matching. all
disappear. There are no internal adjustments or alignments and the choice of power transistor types is less restrictive.

Field service normally requires nothing more than a screwdriver and a replacement module.

Page 3

QURD 52C) instruction book

Keep the packing in case the amplifier has to be sent back to Quad or to the local Ouad distributor lor sen/ice.


The Quad 520 is deSigned for standard 19 inch rack mounting. but can of course be used lree standing. Adequate
ventilation should be provrded and where a number of amplilters are mounted in a rack It may be necessary to use a
cooling lan.


The Quad 520 Is supplied tor use on either 200-240 or lOO-lZOV A.C. supplies and the A.C voltage is clearly
marked on the rear panel. A.C.voltage changes of 6% above or below the indicated range do rtot allect uerlormance
To change lrom 220 to 1 10V operation, the connections at the iunction terminal in the amplifier must be changed
as shown in Fig. 1.

170V 740V
I l l
6 O O 6 O O LI\I(Berttl
l? 0 f 9 9 9

3i :il
:il ' 3i

A C I'm." Cmuwr'nv CE[22-V

A.C. input is via a standard CEE22-V plug and socket. The amplifier chassrs must be connected l0 ground vta the
A.C. supply cord. A Slmple retaining clip ensures that the AC. connectors cannot be removed by accident.

The A.C. supply luse is located next to the A.C. connector. Correct rating for 220V operation is T6,3A and lor 110V
operation T1OA. The AC, connector must be removed to gain access to the luse holder.

The Quad 520 is normally fitted with XLR type connectors. These are wired either to I.E.C. or NAB. standards and
clearly marked on the back panel.

Input - via XLR' typo chluil mounted locket Output - via XLH typo ctr-nit mounted plug
I.E.C. Pin 1 - Blank I.E.C. Pin 1 - Blank
Pin 2 - Line A - Hot Pin 2 - Line A - Hot
Pin 3 - Line B - Cold Pin 3 - Line 3 - Cold
N.A.B. Pin 1) - Line B - Cold N.A.B. Pin 1] - Line B - Cold
Pin 2) Pin 2i
Pin 3 - Line A - Hot Pin 3 - Line A - Hot

Input and output are in phase.


Optimum performance will only be achieved it the amplifier is correctly grounded.

The cold side of the input (unbalanced) must be at or close to chassis potential. The load must not be grounded

Each channel of the amplifier is a four terminal device and care must be taken to ensure that there is no connection
between the cold sides of the input and output.