Owner`s manual

Connecting loudspeakers to the QUAD II – forty (refer to figs. d - g above)
Valve power amplifiers require matching to the loudspeaker for optimum
performance. The QUAD II – forty has three output terminals – Common, 4
Ohms and 8 Ohms. Check the manufacturer's handbook for your speakers
and use the terminal pair that most closely matches your speakers. Even
though a loudspeaker may be broadly defined as 8 Ohms or 4 Ohms its
overall impedance varies throughout the audio frequency range so some
experimentation may be necessary to achieve the best sonic performance.
The following general provisions apply:
For loudspeakers with nominal impedance of 7 Ohms and above:
 Connect the Red (Positive) terminal of the loudspeaker to the 8 Ohm
terminal.
 Connect the Black (Negative) terminal of the loudspeaker to the COM
terminal of the QUAD II – forty amplifier.
For loudspeakers with nominal impedance between 3 and 6 Ohms:
 Connect the Red (Positive) terminal of the loudspeaker to the 4 Ohm
terminal.
 Connect the Black (Negative) terminal of the loudspeaker to the COM
terminal of the QUAD II – forty amplifier.
Some basic cautions:
 NEVER drive loudspeakers using the 4 and the 8 Ohm terminals
together and NEVER short these terminals out.
 NEVER connect or disconnect loudspeaker cables whilst the QUAD II –
forty is switched on.
Connecting cables to the QUAD II – forty loudspeaker terminals:
 Strip any outer sleeve from the cable to a depth of around 40 mm (1.5”).
 Strip the top 7mm of sleeving to expose the bare wire.
 If you are using stranded cable, lightly twist the strands to gather any
loose ends.
 Partially unscrew the knurled portion of the terminal to expose the cross
hole at the terminal base.
 Push the bare end of the cable into the hole. Ensure that the polarity is
correct and there are no loose strands which could touch adjacent terminals.
 Tighten securely.
Connecting the QUAD II – forty power amplifiers
DO NOT REMOVE THE COVER NO USER SERVICEABLE PARTS INSIDE
220V ~50Hz T1.6A Fuse
100V ~60Hz T3.15A Fuse
Fused IEC
Mains Input
Audio
Input
On/Off
Switch
Common
Loudspeaker Terminals
INSTALLATION
If this is your first valve amplifier please familiarise yourself with some issues
surrounding the safe use of the QC – twenty four and QUAD II – forty.
Valves get hot
Valves (tubes) function by thermionic emission, which requires heat.
Additionally, the power amplifiers generate a lot of heat even with no input.
Therefore it is vital to ensure adequate ventilation for your valve equipment
especially power amplifiers.
The power amplifiers should be placed upon a hard flat surface to allow air to
flow into and around the base and valves. As rising hot air from the large
output valves will heat anything placed above, the QUAD II – forty power
amplifiers should not be placed on a rack; each unit should be on its own
well-ventilated platform with at least 1m (3ft.) of free space above it.
Although the cage over the QUAD II – forty’s valves gets hot it is very
unlikely to cause a burn. For absolute safety the units should be placed out of
the reach of children and pets and away from heat-sensitive objects.
The QC – twenty four may be placed in an equipment rack, but ensure that
there is plenty of free space around the unit for good ventilation and that any
component placed above it is at least 200mm (8”) away.
Valve amplifiers work with high voltages
There are high voltages present within these components, as valves require a
high voltage to function. Do not open any of the cases. Also ensure that
nothing is poked, dropped or poured into an amplifier's case.
The environment should be dry and free from litter. You should not place or
store magnetically or thermally sensitive objects (such as credit cards or
optical discs) close to these QUAD units.
Valves are microphonic
Because valves are constructed from fine wires and tiny metal parts they can
pick up external vibrations. For that reason a good, solid isolation support is
recommended. If you place the power amplifiers too close to the speakers the
direct loud sound can vibrate the valves. 1 metre (3ft) to the side of each
speaker should be considered a sensible minimum.
Valve amplifiers prefer high impedances
Solid-state power amplifiers have a typical input impedance of 10k Ohms.
This is really too low for a traditional valve preamplifier. The recommended
minimum load impedance for the QC – twenty four is 50k Ohms.
The QC – twenty four will function well with most if not all valve amplifiers,
and the QUAD II – forty will function with virtually any preamplifier.
Interconnects and Cables
Cables that are used with QUAD equipment should be properly terminated
and appropriate to the task.
To connect the QC – twenty four to the QUAD II – forty amplifier the
equipment uses RCA phono plugs at each end of a screened cable. Such
cables are also used to connect the QC – twenty four to other audio sources.
Interconnects are electrically capacitive. In other words, their impedance
starts to drop with increasing frequency. A limit of 10ft (3m) should be
placed upon the length of interconnect between the QC – twenty four and
QUAD II – forty. This will also minimise noise pickup in the cables.
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3W - 6W
7W - 16W
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