FirstWatt-F4-pwr-维修说明书手册含电器原理图

First Watt model F4Operation and Service ManualIntroductionAnyone paying attention is aware that First Watt makes unusual amplifiers withthe emphasis on performance at low power levels.Here's another oneThe F4 is Class A impedance converting amplifier,having no voltage gain orfeedback.Its input impedance is 48,000 ohms,and its output impedance is about0.2 ohms.It is suitable for driving a high sensitivity loudspeaker with the outputvoltage of a preamp or other line-level audio source.It is also useful with a lesssensitive loudspeaker in a bi-amped configuration where it takes input from theoutput of a conventional amplifier.As a stereo amplifier with single-ended inputs and outputs,it will deliver up to 25watts into 8 ohms with a damping factor of 40.It will do 50 watts into 4 ohms,andas a mono-block amplifier with parallel inputs and outputs,it will do 100 watts into2 ohms.As a mono-block amplifier with balanced inputs and outputs the power outputrating is 100 watts into 8 ohms at 0.5%,and the damping factor is 20.At ordinary listening levels the amplifier operates Class A,and the distortion is 2ndharmonic in character,rising or declining in linear proportion to the output power.The amplifier has a direct coupled input and output,with a-0.5 dB rolloff around.1 Hz and 200 KHz,and it does a clean square wave at 100 KHz.The combination of a simple Class A circuit operated without feedback and theexcellent objective performance gives us a superb sounding amplifier.The lowdistortion,bandwidth extension,and high damping results in midrange clarity,treble detail,and control on the bottom end.While these are available from most good solid state amplifiers,the F4 also bringsdepth,imaging,midrange warmth and top end sweetness.Overall,it is one of the best sounding amplifiers,and if you can live with unityvoltage gain in your amplifier,it is possibly your best choice.