Crown cts1200 Guía De Referencia
what has become known as "constant voltage" distributed systems. (Radio Physics Course 2nd Ed., Radio
Technical Publishing co., N.Y., 1931).
Various voltages have been tried such as 25, 35, 50, 70, 100, 140, and 200 volts, but the 70V system has
become the most widespread.
After World War II, we find constant-voltage systems depicted in such reference works as Radio Engineering
3rd Ed. (McGraw-Hill, N.Y., 1947). By the end of that decade, several standards had evolved to regulate
70V specifications for amplifiers and transformers. (Radio Manufacturer's Association, SE-101-A And SE-
106, both from July 1949). In the 1950's we find the use of 70V systems very well established as evidenced
by Radiotron Designer's Handbook 4th Ed. (RCA, N.J., 1953 and Radio Engineering Handbook 5th Ed.
(McGraw-Hill, N.Y., 1959).
As component design improved, 70V systems began to achieve high-fidelity status, but there were two weak
links in the chain: the step-up and step-down transformers. Good broadband transformers that could resist
core saturation and distortion were expensive. Half of this problem was solved in 1967 When Crown
International introduced the DC-300. It was most likely the first high-powered low-distortion solid-state power
amplifier capable of directly driving a 70V line without a step-up transformer. And in June 1987, the Macro-
Tech 2400 was introduced with the capability of directly driving a 100V line. Thus, today only the
loudspeaker needs a transformer to step down the voltage.
APPENDIX: Transformer insertion loss
Transformers have insertion loss (power loss due mainly to resistance). This loss should be included in
system calculations for precision.
Converted to a power ratio, insertion loss can be expressed as
PR = 10
Technical Publishing co., N.Y., 1931).
Various voltages have been tried such as 25, 35, 50, 70, 100, 140, and 200 volts, but the 70V system has
become the most widespread.
After World War II, we find constant-voltage systems depicted in such reference works as Radio Engineering
3rd Ed. (McGraw-Hill, N.Y., 1947). By the end of that decade, several standards had evolved to regulate
70V specifications for amplifiers and transformers. (Radio Manufacturer's Association, SE-101-A And SE-
106, both from July 1949). In the 1950's we find the use of 70V systems very well established as evidenced
by Radiotron Designer's Handbook 4th Ed. (RCA, N.J., 1953 and Radio Engineering Handbook 5th Ed.
(McGraw-Hill, N.Y., 1959).
As component design improved, 70V systems began to achieve high-fidelity status, but there were two weak
links in the chain: the step-up and step-down transformers. Good broadband transformers that could resist
core saturation and distortion were expensive. Half of this problem was solved in 1967 When Crown
International introduced the DC-300. It was most likely the first high-powered low-distortion solid-state power
amplifier capable of directly driving a 70V line without a step-up transformer. And in June 1987, the Macro-
Tech 2400 was introduced with the capability of directly driving a 100V line. Thus, today only the
loudspeaker needs a transformer to step down the voltage.
APPENDIX: Transformer insertion loss
Transformers have insertion loss (power loss due mainly to resistance). This loss should be included in
system calculations for precision.
Converted to a power ratio, insertion loss can be expressed as
PR = 10
(L/10)
where
PR = power ratio
L = insertion loss in dB (always a positive number).
Some transformer manufacturers compensate for insertion loss by adding extra windings. In that case, the
power delivered to the speaker is the rated value of the tap. The primary draws the rated power times the
power ratio of the insertion loss. In this case, you can calculate the primary impedance as follows:
Pt = Ps + L
where
Pt = total power in dBm
Ps = power to the speaker in dBm
L = insertion loss in dB
or,
Pt = Ps * L
where
Pt = total power in watts
Ps = power to speaker in watts
L = insertion loss (as a ratio).
Then the primary impedance is calculated as follows: