Peavey CKS Series - Manual (Page 18)

Appendix E Crest Audio CK Power Processing Amplifiers
A distributed or constant voltage system, as shown in the figure below, uses
loudspeaker step-down transformers for each speaker. The transformers are
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
both, so it can be used for several different power levels or speaker imped-
ances.
Each speaker step-down transformer converts the low impedance of its loud-
speaker to a relatively high impedance as seen by the distributed line.
Consequently, loads can be added or subtracted to the distributed line with
very little effect on the actual line voltage, hence the term “constant voltage.”
The actual line load Z that the amplifier “sees” is determined by the formula
Z = V 2 /P
where P is the sum of the loudspeaker power taps, compensated for trans-
former insertion loss;
(P = X [xfrmr#1] * P [speaker#1] + X [xfrmr#2] * P [speaker#2] + ...),
and V is the distributed line voltage. So, for a 70.7 volt line,
Z = (70.7) 2 / P
Z = 5000/ P
For example, if the total power demanded by the speakers is 200 watts, then:
V 2 /P = 25
The compensation factor for transformer insertion loss is:
x = power drawn from distributed line
power delivered to speaker = 10 Insertion loss (in dB)/ 10
Therefore, a speaker transformer with an insertion loss of 1 dB, tapped at 4
watts, will actually demand 1.26 times 4 watts, or about 5 watts.
CKV Series amplifiers are specifically designed for use with distributed or
constant voltage systems. Each CKV Series model can drive two distributed
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
power including insertion losses does not exceed the rated power of the
model chosen.
If the impedance of a distributed line overly stresses the amplifier output
stage, the amplifier’s IGM protection circuits engage, reducing gain in order
to protect the amplifier.
Appendix E - Distributed / Constant Voltage Systems.