Appendix E Distributed / Constant Voltage Systems

Appendix E - Distributed / Constant Voltage Systems.

A distributed or constant voltage system, as shown in the figure below, uses

loudspeaker step-down transformers for each speaker. The transformers are

For example, if the total power demanded by the speakers is 200 watts, then:

designed to deliver a specific power level into a specific load impedance

when a specific voltage (the example here uses 70.7 volts) appears at the pri-

mary. A speaker transformer usually has taps on its primary, secondary, or

The compensation factor for transformer insertion loss is:

both, so it can be used for several different power levels or speaker imped-

x = power drawn from distributed line

Each speaker step-down transformer converts the low impedance of its loud-

Therefore, a speaker transformer with an insertion loss of 1 dB, tapped at 4

speaker to a relatively high impedance as seen by the distributed line.

Consequently, loads can be added or subtracted to the distributed line with

watts, will actually demand 1.26 times 4 watts, or about 5 watts.

very little effect on the actual line voltage, hence the term “constant voltage.”

CKV Series amplifiers are specifically designed for use with distributed or

The actual line load Z that the amplifier “sees” is determined by the formula

constant voltage systems. Each CKV Series model can drive two distributed

Z = V2/P

lines (one per channel) of the type for which they are configured, any number

of tapped loudspeakers can be placed on a line as long as the total demanded

where P is the sum of the loudspeaker power taps, compensated for trans-

power including insertion losses does not exceed the rated power of the

former insertion loss;

model chosen.

(P = X [xfrmr#1] * P [speaker#1] + X [xfrmr#2] * P [speaker#2] + ...),

If the impedance of a distributed line overly stresses the amplifier output

and V is the distributed line voltage. So, for a 70.7 volt line,

stage, the amplifier’s IGM protection circuits engage, reducing gain in order

to protect the amplifier.

Z = (70.7)2 / P

Appendix E

Crest Audio CK Power Processing Amplifiers