The veteran and renowned Swedish firm Copland, one of the most traditional High Fidelity icons, has just launched the CTA407 on the market, a stereo integrated amplifier with 100% valve architecture which was born with the objective of enhancing the role of the aforementioned component as an interface between the signal sources and the speakers, in order to bring the restitution of music to its highest levels of naturalness. Of this distinguished electronics, the first thing to be highlighted is the fact that its creators have compromised the usual conceptual simplicity of Copland’s creations by introducing a complex circuitry intended to support the audio stages. Thus, the 40 LEDs on the front panel (10 for each of the 4 power valves) are the visual part of the polarization management and valve diagnosis system that it incorporates, although they can be deactivated if the user so requires. want it.
As far as compatibility is concerned, the new Copland is will automatically adjust acany outlet valve from the 6550/KT88/KT120/KT150 family, thanks to a key innovation: a servo system that not only adjusts the bias automatically and without losses, but also is an integral part of the device’s internal high-pass filtering circuitry, closely matched to the transfer function of the amplification section. Also the connectivity has been very careful, with five line inputs (including a loop in/out for monitoring recordings) and one phono input (accommodating moving magnet cartridges and high output moving coil cartridges) based on that of the celebrated CTA405 model. As for the output stagesare push-pull type and consist of two power valves mounted in a fixed ultralinear arrangement that simultaneously provide the low distortion of the triodes and the generous output of the tetrodes. In fact, a pair of 6550 and KT family tubes mounted in push-pull can deliver more than 100 watts.
Moderating this figure, the CTA407 supplies 2×50 watts in Class A/AB high bias, which means that in practice the amplifier can supply most of its power in A class. On the other hand, as a consequence of the outstanding quality of the output transformers, a superb linearity before applying feedback, thus reducing the costs inherent to the use of internal compensation circuits and ensuring a high stability before closing the loop with 18 dB negative feedback. The result of this thoroughness is a extraordinarily accurate music restitution without the slightest tendency to listening fatigue, to which is added robust dynamics and great flexibility when choosing speakers.
