Wiring:The Two-Point Earth MethodI use the two-Point Earth Method to reduce AC hum. With this method, I don't need DC heating of the final tube's filament. Please observe the schematics again. The earth symbol with "S" refers to "earth of Signal". "P" is as "earth of Power supply." I use heavy bare copper wire with a diameter of more than 3mm for the main earth buss. The signal earth buss is connected to the input terminal and the other end is connected to speaker output terminal. This line connects with the chassis at one point near the input terminal. The power supply earth line connects with the chassis at one point near the power transformer. All ground points are connected to the signal earth line. However, don't connect the end of earth line with the chassis before finishing all wiring and soldering. When the wiring is finished, touch the probes of the tester to the chassis and the earth line. If the tester shows no current, then you can connect earth line to chassis. Unfortunately, if the tester indicates cur-rent, you must search and correct a short somewhere in the circuit. Many amplifier builders bundle and tie the wires together. A Iot of noise and AC hum results from this practice. Although the inside of my amplifiers are not beautiful like the rich catalog pictures of commercial products, my amplifiers don't need DC current for the output tubes! The picture of the underside of one of my amps above shows you the wiring technique. Although this is not the 845 amplifier discussed in this article, it will serve to illustrate my method. |
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Throughout the time I am wiring it, the amplifier rests on the round table. This table is the best spot in the Concorde restaurant to enjoy both food and sound. Customers sit at this table. They eat and drink with little notice of this monster amplifier laid before their noses. I don't mind, because their frank criticisms have made my sound. It is easy to earn five stars on my food but it is very hard to get even one star for audio! |
