appendix
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26
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care and maintenance
fuses
There is a fuse in the
power socket on the
back of your 250x3R.
To change the fuse,
unplug the power cable
and carefully pull out the
fuse carrier drawer
(1)
.The fuse carrier
contains a spare fuse; this is the first one
that you see when you open the carrier.
There are no other user-serviceable parts
inside the 250x3R.
cleaning
In order to maintain the appearance of
your 250x3R, you can clean it as follows:
• before cleaning always disconnect
your 250x3R from the AC supply;
• any grease or dirt on the case may be
removed with a soft, lint free dry cloth.
Do not use any other solutions. Do not
use water or any solvents or abrasives;
• take great care not to get any liquid
inside the case. If this happens, you
should have your 250x3R serviced.
ser vice
The only service you should do to your 250x3R is described on the previous page. All other
servicing should only be carried out by one of our authorised service agents.
If service is required, please contact your authorised TAG McLaren Audio retailer. If your
250x3R is still under guarantee, please refer to the guarantee card which gives you details
on how to claim against the guarantee.
Please keep the original packaging and use it whenever your 250x3R is transported.
1
You cannot open the fuse drawer while the plug is in the socket
about balanced inputs
Balanced inputs are an extremely effective way of providing clean signals to an amplifier
even when the surrounding conditions are less than ideal. A balanced input has three
connections- typically the three pins on an XLR connector. Standard practice is for Pin 1 to
be Ground, Pin 2 to be the “hot” or in-phase connection, and Pin 3 to be the “cold” or
phase-reversed connection.
A major advantage of balanced interconnects is the complete suppression of ground-loop
problems. If a ground-loop is present, then mains-frequency currents can flow down the
ground of the interconnect between a sending unit and a receiving unit. If the receiving unit
has an unbalanced input this noise is indistinguishable from the signal, being effectively
added to it, and is heard as a hum or buzz. A balanced input, however, does not respond
to the voltage between input and ground, but to the difference of its two inputs. Therefore
when the hot and cold connections are made to the sending unit the unwanted voltage that
exists on the interconnect ground is ignored.
For this system to work well, it is important that the balanced input performs an accurate
subtraction of the signals at its two inputs. The measure of how well it does this is called the
‘common-mode rejection ratio’. In the 250x3R this is more than 40 dB, or one hundred
times, and this is permanently fixed as it is set by precision resistors rather than by
attempting to balance variable semiconductor properties.
GRR00723.09-UK 250x3R.qxd 31/10/01 3:40 pm Page 26
