At this point you should be able to listen to music.
The power supply of the amplifier is isolated from the chassis and AC earth
ground by a thermistor which connects the circuit ground to the chassis and earth
ground. This helps to prevent ground loops, but the thermistor stands by to
conduct AC line voltage to ground until the fuse blows in case of transformer or
other such failure.
The input impedance is 100 Kohms, and the input capacitance is very low, so you
will find it easy to drive it with single-ended tube equipment if you like.
The J2 has enough damping factor at 20 to work well with loudspeakers that mate
well with tube amplifiers in general, and it delivers good performance into 4 ohms
also – see the distortion curves at the back of this manual. It is designed around
relatively high efficiency speakers and it particularly shines with those that have 90
dB/watt sensitivity or greater, but you can hook it up to anything you like, as long
as you adjust your expectations as to how loud it will play.
The amplifier requires about 1 hour of operation to reach normal operating
temperature, and this warm-up time is appropriate for the most critical listening,
but is not otherwise an issue. The amplifier’s final adjustments were been made
after an hour, but the performance difference between 1 minute and 60 minutes is
not very great.
I do not personally see a reason to run the amplifier all the time, but you can do
that if you want to. The power supply capacitors are likely to last about 15 years
or so, and while they will slowly dry out just sitting there, they will have a shorter
life span with the amplifier running constantly. Also, at 200 watts it makes
economic sense to shut the amplifier off if you aren’t planning on using it for the
rest of the day.
Again, the heat sinks on this amplifier run fairly hot, and you want to make sure
that they get adequate ventilation. They will run at around 25 degrees C. above
the ambient temperature, which puts them around 50 degrees in the average
listening room. At this temperature you should be able to put your hand on them
for about 5 to 10 seconds or so.
If you have any questions, contact First Watt. I answer all questions, even if the
answer is no.
www.Firstwatt.com nelson@passlabs.com
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