D-fend SA300 User Manual - page 12
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D-fend™ SA300 User Manual
Tweeter Protection
In Figure 2.3, we have an example of a planar ribbon tweeter typically found in a high end studio monitor. Often these
tweeters are powered by their own dedicated amplifier as shown in our example. Here the output of the amplifier, a 300
watt per channel into 8 ohm unit, is connected to the input of the SA300. The tweeter is an 8 ohm 50 watt unit connected
to the output of the SA300. Actual programming of the SA300 will be covered in the Advanced Programming section on
page 17.
Notice there is an external power supply being used with the SA300 in this example. The use of an external power supply
(sold separately) will allow the user to protect the tweeter at a very low voltage level if needed (below the normal threshold
of basic D-fend operation). It gives extremely fast reaction times and provides the ultimate in sound quality. Typically the
SA300 will be powered by the audio signal, but there are situations where using external power will be best. Protecting a
$1,000 ribbon tweeter is one of those situations.
25-70-100 Volt Distributed Systems
Attention! The SA300 can not be used AFTER an audio transformer.
The SA300 can be used in 25 and 70 volt distributed systems that use either a transistorized high voltage, low output
impedance direct drive amplifier (without an internal step up transformer) or with a normal amplifier and an external step-
up transformer. If you are not sure if your amplifier has an internal transformer you should contact the manufacturer of
the amplifier, or you can call us and we will try to research it for you. If in doubt, do not connect the SA300. If you use the
SA300 after an audio transformer, system damage and damage to the SA300 can occur.
Most modern amplifiers designed to drive 25, 70, or even 100 volt systems do not use internal step-up transformers. In
this case, the SA300 will be connected to the output of the amplifier and the output of the SA300 will be connected to the
lines that drive the small step-down transformers at each speaker. Please see fig 2.4 for proper connection of the SA300 in
a 70 volt distributed system using a high voltage direct drive amplifier. Again, only connect the SA300 to the output of your
amp if you are 100% sure there are no internal output transformers.