Petr Žwak - tube amplifiers

Jupiter - MM phono tube preamplifier

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	Used tubes	6N21B, 6N17B-V, 6N16B-V for each channel
	Optimal input	1.5 mV - 5 mV / 47 kOhm
	Optimal load	47 kOhm / 80 pF - 1000 pF selectable
	Gain	50 dB / 44 dB optional / 1 kHz
	THD distortion	max. 0.05% in the range 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)	min. 78 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 Jupiter for MM phono cartridge is designed with sound quality in mind and meets even very high demands. It is equipped with selected components of high quality with regard to the durability of the device and the desired sound expression. No semiconductor element is used in the audio path, only triode tubes.

The preamplifier uses two active stages in Mu Follower topology, between which a passive RIAA filter is inserted. The first stage is equipped with a low-noise 6N21B. The second stage uses 6N17B-V, both stages allows you to achieve high gain with low distortion. At the output, a White Cathode Follower with 6N16B-V is used, which thanks to its low output resistance allows optimal excitation of the following amplifier even with a longer line. The preamplifier has no global negative feedback (NFB) and the tubes are matched so that the channel gain difference does not exceed +/- 0.2 dB over the entire frequency range. The preamplifier is equipped with extended life tubes (military types, paired). Gain switching of -6 dB allows to adapt the preamplifier to MM cartridge with higher output voltage, or to reduce the gain in case of overdriving of the subsequent amplification stage. On the other hand, due to the higher gain, for optimal output also can be used cartridge with lower output voltage. The load of the MM cartridge can be selected between 80 - 1000 pF. The preamplifier is designed in two separate cabinets to suppress source interference. Cabinets can has silver or black front pannel. Both the preamplifier and the power supply (PSU) are microprocessor controlled to provide the optimum on/off sequence to ensure the highest possible tube life. The microprocessor also monitors the internal temperature of the preamplifier against overheating.