Saturday, December 28, 2013

S.A. Lab Erato























































Output transformers - 65kg each


















System price - €112,000

Tubes

Preamplifier. The WE310 pentode (Western Electric, USA 1939) was used in early cinema projectors to drive a 300В. Here this very linear tube works as a pentode whose second grid is stabilized parametrically. The main advantages of the current-production Bulgarian 40 output triode are high linearity of the volt/ampere characteristic and low distortion. The power supply stabilizers are two 6AS7, two 6ж4, two с201г (USSR, 1954) and two VR-150 (France, 1957).

Power amplifier. The mighty ГУ-80 pentode (Erato uses a Soviet specimen from 1962) is an exact replica of Telefunken's RS384 which was in active use by the Nazi Wehrmacht from 1939 on. This output tube works in triode mode with perfect parameters of 450W anode power, 500mA quiescent current and low internal resistance for a reasonably high damping factor into any load. This tube is very linear. The US VT-25 input triode (late 1950s) was designed and originally used as an output or driver tube in low-frequency amplifiers. It has high linearity and substantial initial current. Here it works as a 300B driver. Because of its high anode voltage and perfect linearity the 300В triode became the chosen output driver. Erato's high-voltage power supply uses modern tubes made in Russia's Saratov. The power supply stabilizers use two 6AS7 (Canada, 1970s), two 6ж4с (Светлана, 1964) and four сг4 (1967).


Specifications

Erato preamplifier
Output voltage: 12V
Frequency response (max. power), 50Hz to 45'000Hz
Output impedance: 9Ω
Signal-to-noise ratio: 90dB
THD (100 Ohm): 0.03%
Input impedance:< 100k
Power consumption: 370 watts


Erato monaural amplifier
Output stage mode: Single-end class А1/А2
Output power (4/8А1, 0.4% ): 75/42 watts
Output power (4/8Ω, А2, 0.6%), 102/60 watts
Frequency response (max power), 10Hz to 40'000Hz -1dB
S/N ratio: 95dB
THD (half power): 0.08%
Output impedance: 0.5Ω
Sensitivity: 7.5V
Input impedance: 275Ω
Power consumption per channel: 950 watts


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