Усилители мощности моно — Trafomatic Audio Pandora

The Pandora is a push-pull Class A monoblock from Trafomatic Audio built around Svetlana 811-10 direct heated triodes. Each chassis delivers 40 W in pure Class A and is hand built in Serbia by the company founded by Sasa Cokic. The monoblocks are offered in black or white finishes.

Key specs that matter

Input sensitivity is 1.4 Veff at the XLR input, which is the only input fitted, and input impedance is 47 kOhm. Gain is 28 dB. Output taps are provided for 4 and 8 ohm speakers. Distortion is 0.2% at 1 W and 1 kHz, noise sits 88 dB below the signal, and the bandwidth runs from 10 Hz at minus 1 dB to 90 kHz at minus 2 dB. A selector on each unit sets the mains supply to either 230 V at 50 Hz or 115 V at 60 Hz, and consumption is 280 VA. Each monoblock measures 340 mm wide, 480 mm deep and 270 mm high and weighs 32 kg.

Engineering and use context

Each amplifier runs two 6N30P driver valves and two SV 811-10 output triodes, with the SV 572-10 listed as the alternative output tube. A Lundahl LL1592 line input transformer performs phase splitting with a high degree of symmetry, which is why the input is balanced only. The stages combine direct coupling with interstage transformer coupling, and an interstage transformer feeds the 811-10 grids. Negative feedback is limited to 3 dB and applied only in the output stage as cathode feedback. Trafomatic uses no capacitors in the signal path. All tubes are heated with DC to lower the noise floor. A C-L-C filter smooths the anode voltage, using Mundorf MLytic HV parts together with a choke of high inductivity wound by Trafomatic. All transformers and the choke are made by Trafomatic. Each Pandora houses an oversized output transformer weighing 6 kg, wound on a double C-core and potted in epoxy resin, alongside an oversized 10 kg power transformer that also uses a double C-core. The output transformers are highly sectioned with harmonically sized sections to keep leakage inductance to a minimum.

Pairing

A stereo system needs two units and a preamplifier with balanced XLR outputs, since the LL1592 input transformer accepts only a balanced signal. Speakers of either nominal impedance can go to the matching winding of the output transformer, and the two finishes allow the pair to be ordered in black or white.

Alternatives

Trafomatic Audio also makes the Glenn, a parallel single-ended monoblock using two 300B direct heated triodes per chassis.