Интегральные усилители — Closer Acoustics 300B Provocateur Signature Edition

The 300B Provocateur Signature is a single-ended triode integrated amplifier from Closer Acoustics, a Polish brand based in Jastrzebie Zdroj in Silesia. The circuit was designed by Robert Rolof and the external design is by Jacek Grodecki. The Signature is the upgraded version of the standard 300B Provocateur, and Closer Acoustics prices it at EUR 8,907. Chassis and transport cases are the work of Andrzej Grodecki.

Key specs that matter

A single 300B triode per channel forms the class A output stage, giving 8 W into 8 ohms. Drivers are CV-181 double triodes, equivalent to the 6SN7, and a 5U4G rectifier tube supplies the high voltage, with Psvane tubes throughout. Frequency response is 18 Hz to 23 kHz within 2 dB, THD is 0.3% at 1 W and channel separation exceeds 70 dB. Four line inputs have a sensitivity of 200 mV and an input impedance of 100 kohm. The case is 400 mm wide and 455 mm deep, stands 198 mm high at the body and 325 mm including tubes, and weighs 28 kg.

Engineering and use context

Over the standard model the Signature adds output transformers with amorphous cores, higher grade tubes and a choice of RCA or XLR inputs. Its circuit board was redesigned with gold-plated traces, and V-Cap ODAM capacitors and Amtrans AMRG resistors are fitted. Polypropylene capacitors are used in the signal path and power supply circuits, with electrolytic types kept to the heater circuits only. A Khozmo resistor ladder attenuator with 48 steps controls the level, driven by a motor which lets the listener change level from the supplied remote handset. Speaker terminals and RCA inputs come from the WBT nextgen series, and power enters through an IEC socket. The cabinet uses plywood sides with black acrylic top, front and back panels, the Signature covers the plywood in Italian Alcantara, and knobs and feet are made from Corian. Custom finishes are available.

Pairing

With such low output power, speakers of high efficiency are the logical match, so horn or wide-range designs with a sensitivity well above 90 dB suit it better than low efficiency multi-way boxes. Any line level source, from a network player to a phono preamplifier, connects straight to the four inputs, and buyers who run balanced cables can order the XLR input option. The attenuator makes a separate preamplifier unnecessary.

Alternatives

The Closer Acoustics 300B Provocateur in its standard version uses the same single-ended 300B circuit without the amorphous core transformers and Signature component upgrades.