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Re: shared versus separate filament suppies....

Posted by Tre' (P) on January 21, 2007 at 08:51:28

In Reply to: Re: shared versus separate filament suppies.... posted by Vinnie on January 21, 2007 at 03:31:24:

Some talk of "primary" and "secondary" (order of importance) audio path.
I won't argue with them but any part where the voltage or current is being modulated by the audio is in the signal path.

Example;

"Grounded cathode gain stage"

Parts list;
1. Grid resistor
2. tube
3. cathode resistor
4. cathode resistor bypass cap
5. plate resistor
6. decoupling capacitor (last cap in power supply just before the plate resistor)
7. coupling cap (the cap the feeds the output signal to the next stage)
8. next stage grid resistor.

1. This one's obvious. This is as far as the original signal gets. All other signal is just a response to this signal.

2. It's the changes within the tube, caused by the changing grid bias (input signal) that creates the output signal.

3. The current for the tube flows through the cathode resistor.

4. With the cathode resistor bypassed, only the DC current flows through the cathode resistor, the signal (AC component) of the tube's current flow flows through this cap.

5. All the current (AC and DC) flows through this resistor.

6. This cap is the "path" for the AC component to get back to ground without having to go all the way back through the power supply.

7. All of the usable output signal to the next stage flows through this cap.

8. Back to the grid resistor where it all starts for the next stage.

So all of these parts are "in the signal path".

With DHT's the filament and the cathode are one in the same.

Tre'

Have Fun and Enjoy the Music
"Still Working the Problem"

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