28 Appendix
Amplifi er Application Guide
Frequently Asked Questions (FAQs)
Q. How can I-Tech produce so much power with only a 20A plug?
A. The combination of Class-I technology and an innovative PFC power supply enables I-Tech to very effi ciently
draw power from the A/C mains and deliver it to the speakers. This high effi ciency, coupled with a signifi cant
amount of energy storage, allows I-Tech to deliver high power much more effectively than conventional designs,
and thus reduces the demands on the power cord.
For more information, read this short “Tech Made Simple” article:
http://www.crownaudio.com/pdf/amps/137331.pdf
Q. Isn’t Class-I just like other amplifi er classes?
A. No, Class -I amplifi ers are a fundamentally different design from all other amplifi er classes on the market.
Crown has patented the technology behind Class-I amplifi ers and is the only manufacturer in the world building
this design.
For more information about Class-I, read this technical paper:
http://www.crownaudio.com/itech/pdf/137234.pdf
Q. How does I-Tech recycle energy from the load?
A. Class-I is unique in that it always provides an electrical path between the amplifi er’s output and power supply
bulk capacitors. This means that when a loudspeaker sends energy back to an I-Tech amplifi er it stores it in the
power supply for later use. This keeps the output devices from dissipating the energy from the loudspeaker as
heat and keeps the power supply from having to work as hard.
Q. Why is the 2 ohm power number smaller than the 4 ohm power number?
A. The question may be better stated, “Why is the 4 ohm number so large?” The 4 Ohm number is so large
because Class-I is not fundamentally voltage limited, unlike ALL other amplifi er designs available on the market.
Competitive amplifi er designs require complicated multi-level (Class-H) supplies, which limit the voltage avail-
able to the output under low impedance loads. This multiple step supply topology lends itself to the typical power
matrix.
The down side of Class-H is that if the program material asks for a peak higher then the rail voltage limit the
amplifi er will distort. In other words, headroom is limited. Class-I does not exhibit this limitation. 200V is always
available to all loads. As a result the amplifi er is capable of producing very high music output peaks without dis-
torting.
Some view I-Tech’s unconventional power matrix to indicate that I-Tech is not “good” or is “unstable” when driv-
ing low impedance loads. Nothing could be further from the truth. A fundamental advantage of Class-I is that it
cares little about the load impedance. Pile on the speakers. I-Tech isn’t afraid.
Q. How does Crown measure power?
A. I-Tech output power is measured using the “Maximum Average Power” method. The Maximum Average Power
test is designed to be an easy way to more closely approximate output power with real world musical sources. The
test is simple: the amplifi er is set up with the level controls turned to the maximum setting, and then a connected
sine wave source is increased until the specifi ed total harmonic distortion is reached.
Q. What are your 20Hz to 20kHz specs?
A. All output power specs for I-Tech are provided at 20Hz to 20kHz.
Q. I heard that PFC could cause the mains to sag and shut the amplifi er down. Will I-Tech’s PFC do that?
A. No. I-Tech monitors the mains voltage and gently corrects for this rare phenomenon.
Q. Are you going to produce a lower-cost version of I-Tech?
A. When compared to retail pricing of competitive amplifi ers with similar specifi cations you will fi nd that I-Tech is
priced VERY competitively, and none of those competitive amplifi ers have DSP, 200V rails, or global power supply
with PFC.
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