![]() Most amps require an input drive voltage of 1.5V RMS - the SFL-2 has a maximum drive voltage of 30V RMS! Certainly no concern about ANY music peaks being limited by the preamp! This is another one of those products you have to be at least passingly familiar with to appreciate its performance and value. 2Hz (yes, two) to 100 KHz at 0.5 dB down (350 KHz at 3dB down!) - no question at all that any harmonics are going to be attenuated. So let’s look at one or two aspects of the measured performance. The digital circuits are completely separated from the main circuit board by a physical metal partition in the preamp, and so it goes. The volume control is not the usual high-end Alps potentiometer but a switch with a resistor ladder on it (the time taken to actually make this component must be measured in hours). Only the best resistors available are used, incuding Caddock and Vishay resistors. Most preamps use a winding from the mains transformer of 6.3V A/C to supply the tube heaters - not only does the SFL-2 use DC for this purposes (to avoid any possibility of hum transfer), but it is regulated DC! Moving on to the preamp itself, all wire and RCA sockets used are from Kimber Kable. There are FIFTEEN regulators in this power supply!!! Most preamps have two or three. Not only that, but this is a dual mono power supply - nothing shared between the two channels, including the transformers! No electrolytic capacitors are used in this power supply - they are metalized polypropylene capacitors, which are considerably more expensive but they sound better. The power supply is 2/3rds of those 55lbs and is built like a tank.in fact, here is part of a user review I saw: Now when SF say "The goal was to build the best preamplifier available making absolutely no compromises", they seriously, SERIOUSLY mean it! This is a preamp with a separate chassis for the power supply. If you look at the pictures, you will see two units.one being the actual preamp, the other the power supply. This thing is 55 pounds of dead-quiet tube sound that has been used for comparison at Stereophile for SO many of their preamp reviews from this unit's time period (1993-1997). Note that it is a line stage preamp, so no phono section. It is in excellent condition and used recently and fully tested in Jan of 2012. This is from Sonic Frontiers golden age and it is such a shame that Anthem (who owns the brand now) doesn't return such amazing two-channel tube audio to Canada. You are bidding on a Sonic Frontiers SFL-2 tube preamplifier. ![]()
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