Biamp CPA650 - Manual (Page 10)

8
70V MONO-BRIDGE OUTPUT
When using a CPA650 to drive a distributed 70V speaker system, a distribution transformer at the output of the amplifier is not required.
The CPA650 is capable of driving a 70V line directly. In order to protect the amplifier (and in case of amplifier failure, the speaker
transformers) one side of the 70V line must be capacitively isolated as shown below. This is necessary since the bandwidth of the
CPA650 extends well into the low-frequencies, and some protection is required to keep the amplifier from seeing the extremely low
impedance of the 70V line below 100Hz.
The two 100uF / 100V non-polar capacitors wired in parallel form a High Pass Filter at 100Hz. In addition, they provide DC protection in
case of amplifier failure. Any equalizer in the signal path should not have the low-frequencies boosted, since this will excessively load the
amplifier. All bands below 125Hz should be flat or cut only. If more low-frequency is needed, a directly driven sub-woofer should be used
to extend the low-frequencies below 100Hz.
output 2 output 1
+ + --- ---
325W/4
Ω
325W/4
Ω
100uF
100V
non-
polar
100uF
100V
non-
polar
speaker
positive
speaker
negative