Усилители мощности стерео — Aries Cerat Diana Forte

The Diana Forte is a two-channel amplifier built by Cyprus-based tube specialist Aries Cerat, and completes the company's Diana series alongside the Diana integrated and the Diana Mezzo preamplifier. Its circuit takes the output and driver stages of the Diana integrated and scales the output section up to more than twice the power, and the company places it among the most powerful single-ended triode stereo amplifiers built. It was launched in the US at around 27,500 dollars.

Key specs that matter

The Diana Forte delivers 60W per channel in single-ended Class A, with about 70W peak. Its output stage uses paralleled 813 tubes, two per channel, driven by an 814 tube per channel operated as a triode, for a complement of four 813s and two 814s. Power bandwidth extends from 15Hz to 110kHz, combined gain is 26dB (x20) and the noise floor is quoted at 100dB. The chassis measures 570mm wide, 590mm deep and 350mm high, and weighs 110kg.

Engineering and use context

Paralleling two 813 output tubes per channel keeps the output stage single-ended, with no push-pull pair splitting the waveform, while doubling the current available to the output transformer. That transformer uses an oversized core and special winding methods so bandwidth stays wide at full power, where single-ended transformers usually lose extension. The 814 driver is loaded by a double-C-core, bifilar-wound interstage transformer, and all stages use Aries Cerat's AC link coupling instead of coupling capacitors. The same AC link connects the Diana Forte to the Diana Mezzo preamplifier, so the pair works as a two-chassis version of the Diana integrated, and owners can buy the preamplifier first and add the power amplifier later. The output stage has two completely separate choke-filtered capacitor banks built from the company's film super-capacitors, specified with ESL and ESR about 100 times lower than electrolytic types, while the driver stage has its own choke-filtered supply and separate power transformer to prevent crosstalk between supplies. Two meters on the top plate let every tube be biased and monitored during listening, and the amplifier can act as a simple tube tester for matching replacements.

Pairing

Its output lets the Diana Forte drive a much wider range of loudspeakers than typical low-power SET amplifiers, although speakers of good sensitivity remain the natural match. It needs a sturdy, well-ventilated floor position given its weight and heat output.

Alternatives

Aries Cerat's own Diana integrated combines a similar all-DHT circuit with a preamplifier section in one chassis, at 25W per channel.