Интегральные усилители — Copland CTA407

The CTA407 is an integrated valve amplifier from the Danish company Copland, built around four push-pull output tubes and fitted with a phono stage and a motor-driven volume control. Copland ships it with KT88 tubes but designed the circuit to take other members of the same family, so owners can change output valves without a technician. British buyers paid GBP 6,500 for it, with either a black or a silver front panel.

Key specs that matter

Rated output is 50 W per channel into both 4 and 8 ohm, and from matched pairs of 6550 or KT-family tubes the amplifier can deliver up to 100 W in high-bias mode. Frequency response runs from 10 Hz to 150 kHz within 3 dB, distortion stays below 0.5 percent at all levels, and Copland states 100 dB for noise, measured IHF-A. Line inputs need 200 mV for full power into a 50 kohm load, and the phono input needs 2.5 mV into 47 kohm. The chassis measures 435 x 215 x 420 mm and weighs 20 kg.

Engineering and use context

Inside, Copland fits four 6550 or KT88 output tubes, a pair of 12BH7 for the driver and phase splitter stages and a single ECC83 in the preamplifier, with one pair of beam tetrodes per channel. The output tubes work in ultra-linear push-pull mode with a high bias, so the amplifier stays in class A for most of its output before moving into class AB. An automatic bias circuit adjusts itself to KT88, KT90, KT100, KT120 or KT150 tubes, and 40 LEDs, ten per output tube, act as a diagnostic system that shows the state of each valve. There are five line-level inputs plus a tape monitor loop, and the built-in RIAA circuit takes MM cartridges and also high-output MC designs. Mains versions exist for 115 V and for 230 to 240 V, and in either version the amplifier draws 300 W from the mains.

Pairing

Because rated power does not rise into 4 ohm, speakers with an easy load and good efficiency make the best partners, especially where high levels are needed. A turntable with a moving magnet or high-output moving coil cartridge connects directly, while low-output MC pickups have to go through an extra step-up device first. The Copland RC102A remote handles full control, including the motorised volume.

Alternatives

The Copland CSA100 is a more powerful hybrid integrated amplifier with a valve input stage and a MOSFET output.