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The Optional Phono Stage |
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The Optional Phono Stage |
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Moving Coil / Moving Magnet Phono Preamplifier The quest for better Analog sound can be summed up as the approximation of perfection. Digital on the other hand is the perfection of an approximation. Until such time as the choice of approximation i.e. the limitation inherent to 16 bit 44.1K sampling is increased substantially, it would seem that the premier recording reproduction chain will be analog. It also seems apparent that each format has its own unique set of strengths and weaknesses. Music recorded with an analog format is best served by not overlaying digital shortcomings. Practically speaking the simple truth is that it is not a question of better, both analog and digital sources need a quality implementation in most audiophiles systems. The phono stage for the OM1 is contained on a small daughter board. The expense and sound degradation of an additional set of interconnects required by an outboard phono stages is avoided. Because the phono stage shares the same chassis and power supply as the OM1, including optional battery supply, truly world class performance is available at a surprisingly affordable price. Of course those choosing not to include records in their playback options need not pay even this price as the OM1 is available as a Line Stage Only. The Phono Stage can be configured for either moving magnet or moving coil cartridges. Thanks to the high gain option even the lowest output MC cartridges can be accommodated without the necessity for an interstage transformer. A two-stage design using a passive high frequency filter and active low frequency boost allows independent optimization of the time and frequency domains and avoids interdependence (where correcting one worsens the other). Custom 1% polypropylene capacitors and 0.1% resistors insure the highest RIAA equalization accuracy. DC servo circuitry provides operational ease with a wide variety of cartridges. This servo is socketed and can be removed allowing manual trimming of the DC offset. This "marrying" of the phono stage to a specific cartridge reveals even more of the musical information a truly fine cartridge can recover from a record groove. While some manufacturers offer balanced phono stages pointing to the phono cartridges inherent balanced operation, the unavoidable noise penalty in a balanced design combined with the proven noise free operation of the star ground and battery operation available in the OM1 dictated an unbalanced implementation. The phono stage is designed to provide capacitive and resistive loading appropriate for popular cartridges. Where better performance could be realized for a specific cartridge, Reflection or one of its authorized service vendors can make appropriate adjustments by simply substituting resistors and capacitors. Specifications: Noise floor within 1.5dB of theoretical minimum. Two stage design: passive high frequency filter; active low frequency stage 0.1% Caddock resistors and custom 1% polypropylene caps Moving magnet version: 35dB gain, 47k ohm, 100 pf Moving coil version: 60dB gain, 1k ohm (adjustable) The preamp has an additional 8dB of gain (unbalanced) and 14dB (balanced) A special high gain ( 70 dB) (78 / 84 total) version is available allowing the use of even the lowest output MC cartridges. |
The Optional Phono Stage
About the designer, Stephen Balliet