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Benz Micro Lukaschek PP-1 Phono Preamp
The small size of the PP-1 allows close placement to the turntable, minimizing signal leads from the tonearm. The whole power supply is inboard the PP-1 chassis except for an external power transformer, which is outboard to eliminate magnetic field interaction. The miniature size also allows all circuit components to be very close to one another. This significantly reduces circuit board traces, which could introduce noise and sonic degradation. The PP-1 is optimized for moving coil amplification, thus does not provide switches and/or jumpers for gain setting or resistive loading. This elimination of unneeded circuit junction points preserves the low noise/high performance characteristics of this superb phono preamp.
By using only two transistors in each amplifier stage, perfect stability and extreme fast transient response is achieved. This provides the high degree of transparency and accuracy of the PP-1. High quality double-sided glass epoxy circuit boards with carefully designed topology (CAD) have been applied in order to ensure shortest possible signal paths. Low-noise, matched bipolar transistors were selected for this purpose. All resistors are high quality metal film with 1% tolerance. Within the RIAA network, only 1% polystyrene capacitors have been used, with high quality metalized plastic-film capacitors in the coupling function.
Each channel of the input amplifier stage works around a phase non-inverting two-stage negative feedback amplifier. Available gain is set at 40dB and the upper frequency limit has been set at 650kHz/-3dB. Input impedance has been set at 22k ohm in order to eliminate interconnect cable and phono connector influence on the sound quality. A 10Hz sub-sonic filter has been incorporated between the input stage and the RIAA equalizer.
As with the input amplifier, RIAA equalization has been achieved through an inverting two-stage amplifier of ultra high accuracy (+0/-.5dB within the RIAA standard). Available gain is 22dB/1kHz and it has an extended high frequency roll-off. This section of the PP-1 connects directly to the output of the unit. Total gain of the PP-1 is 62dB, ideal for cartridges with output as low as .2mV.
In his latest revision of the PP-1, Albert Lukaschek has redesigned the regulation circuitry of the unit's power supply, bringing across-the-board improvements in the areas of clarity, focus, and bass control. Integrated circuits are now employed only in the pre-regulator, which provides a constant 25 volts to the independent regulators for each gain stage, which are now implemented with fully discrete transistor regulators.
Benz Lukaschek PP-1 Specifications # RIAA equalization: +/- 0.5dB # Integrated rumble filter: 10Hz (-1dB at 20Hz) # Gain at 1kHz: 1280 (62dB) # Crosstalk: below measuring range # Signal/noise ratio (0.5mV 0 ohm): 82dB (IHF “A”) # Maximum input voltage: 5mV (1kHz) # Input Impedance: 22k ohms