Petr Žwak - tube amplifiers

Mercury - MC/MM phono tube preamplifier

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	Used tubes	2x 2SK170, 2x 6N18B-V and 6N16B-V for each channel
	Optimal input MC	0.15 mV - 0.5 mV / 10 - 1000 Ohm
	Optimal input MM	1.5 mV - 5 mV / 47 kOhm
	Optimal load	MM 80 pF - 1000 pF, MC 10 Ohm - 1000 Ohm selectable
	Gain	MM 50 dB / 1 kHz, MC 70 dB / 1 kHz
	THD distortion	MM max. 0.04%, MC max. 0.06% / 20 Hz - 20 kHz / 0.775 V
	Output voltage nom.	0.775 V / 1 kOhm / 1kHz (max +20 dB overload)
	Frequency range	20 Hz - 50 kHz (RIAA filter correction)
	Deviation from RIAA	max. +/- 0.2 dB
	S/N ratio 0 dB (A)	MM min. 78 dB, MC min. 58 dB
	Power supply	230 VAC / 30 W (0.5 W standby)
	Size (h x w x d)	90 x 135 x 240 mm (one box)

The preamplifier Mercury for MC/MM (selectable) phono cartridge is designed from legendary JFET 2SK170 and triode vacuum tubes with sound quality in mind and meets even very high demands. It is equipped with selected passive and active components of high quality with regard to the durability of the device and the desired sound expression.

The preamplifier uses two active stages, between which a passive RIAA filter is inserted. The first stage is equipped with a pair of low-noise JFET 2SK170 in cascode with a dual triode 6N16B-V or 6N18B-V. The second stage uses the Mu Follower topology with 6N18B-V, which allows you to achieve high gain with low distortion. The output uses a White Cathode Follower with 6N16B-V, which thanks to the low output resistance allows optimal excitation of another amplifier even on longer lines. The preamplifier has no global negative feedback (NFB), the tubes are paired. The topology of first stage allows you to choose to change the gain by +20 dB, so MC cartridge can be used directly without the need for a step-up transformer. The MM cartridge load can be selected between 80 - 1000 pF, MC cartridge load can be selected between 10 - 1000 Ohm. The preamplifier is designed in two separate cabinets to suppress source interference. The cabinets can have a silver or black front panel just like Jupiter. Both the preamplifier and the power supply (PSU) are controlled by a microprocessor to provide the highest optimal sequence / shutdown and thus ensure the life of the tube. The microprocessor also monitors the internal temperature of the preamplifier against overheating.

Photos of PSU Mercury will be added soon, it is very similar to Mars or Jupiter.