I own 3 CA 400's. As a stereo amp they exhibit many of the qualities of tube amps. They're warm, tight, have silky highs and give the listener the impression of limitless power. The bottom end is controlled and capable of a lot of reserve capacity. I run them bridged and this is where they really excel! A liquidity comes forth that is very noticable. In this mode the CA 400 puts out 2400 watts into 4 ohms, 1400 into 8 ohms. The transformer is a toroidal design(3-kVa), with the signal to noise ratio being 137 db. Thd is 0.004%. Running in ballanced mode they are dead quiet. Used, I've seen them as low as 2250$. It's unnecessary to pay more than 2500 for a used CA 400. A bargain for a "monoblock" capable of 2.4 kilowatts! Yet for all their power they can produce all the subtle nuances and, when called for, punch out bass with impressive control. This is due to a massive, shielded transformer which powers the high-speed circuitry. In a lot of high end amps, this power is sent to a small number of large capacitors for distribution. However, large caps are slow in responding to the rapidly fluctuating energy demands of music. While their previous "Top Dog", the M-1000, had 2 large 35000-uF capacitors per channel in its power supply, the CA 400 uses 2 dozen 4700uF capacitors. As a result, the CA 400 has 112,800uF per channel, versus 70,000 for the M-1000. Classe believes that connecting a series of smaller capacitors directly to output devices produces a much faster discharge and reduces power-supply interactions. So...better dynamics and greater detail. This is why the amp is so fast. The CA400 has true differential amplifier circuits from input to output.
All this power needs heat sinks and the 400 has a lot of them. They run warm and this is normal. A ceramic cup of hot coffee is almost too hot to hold. Almost. This is about the running temp of a typical 400. They do not need fans, but do benefit from adequate air circulation. In other words, don't stack a component on the 400.
Most high end amps use only one type of transistor. The 400 uses bi-polar, mosfet and j-fet: all three. This sequence makes the most of their particular voltage and input impedance characteristics.
The amp weighs in at 120 lbs. and shipping runs about 110$ with fed ex, depending on distance. In their original boxes, they are very well protected. It's a plus if the previous owner kept the boxes.
I've used this amp with Thiel 7.2's and currently with Nearfield Accoustics Pipedreams. The sound stage is terrific. The CA 400 never gives up transparancy for power or dynamics for sweetness. Nor does it trade depth for soundstage width or alter the upper octaves to make them more euphonic or to highlight added detail. The CA 400 adds a degree of life and energy to these virtues, with musical excitement rivalling the best musical dynamics and transient response of tube or class A amp designs.
So as you may notice, I like the 400. The amp dates back to 1995, and I've never had problems with any Classe product. They are built to last!
