| Re: K200B-1 left channel makes a loud whooshing sound [message #23283 is a reply to message #23227] |
Tue, 07 July 2015 02:41   |
chicagobill
Messages: 2005
Registered: April 2003
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Senior Member |
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There are two types of transistors in the input stage, one is an NPN and the other is a PNP. Almost any transistor will work in these circuits, but low noise ones are best.
Okay, let's look at the first transistor stage and how the volume pot works to change the gain of the first stage. The gain of the first transistor stage in the preamp is partially controlled by the value of the resistor from the emitter to ground. In rough terms, the lower the value the higher the gain. Because the volume pot is connected to the emitter resistor of the first transistor, the resistance that appears on the volume pot is part of the resistance of the emitter circuit to ground. When the wiper of the volume pot is turned CCW the full resistance value of the volume pot is added to the resistance of the emitter circuit, which reduces the gain of the stage. As the pot is turned CW the wiper reduces the resistance in the emitter circuit until the resistance of the pot is zero in the emitter circuit increasing the gain.
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