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Old 4th August 2012, 03:10 PM   #1
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Default 300b

I want to adjust the flow of two different brands 300B
The strength that I have is 880 ohm adjustable and if I could adjust
You have to drop the resistance I insert the milliammeter of resistance
ground to fine adjust?
Another issue is that capacitors are good for power, I have
a 47uf-600v solen of the input and filter after the shock of two
Mundorf of 47 +47 and the other is the step that I have I have two Dynamicap.
a greeting.The valves 300B gold Lion and Electro-Harmonix
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Old 4th August 2012, 05:16 PM   #2
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Rather than insert an ammeter between the cathode resistor and ground you can insert a 10 ohm resistor. Then measure the voltage drop across the resistor and use ohms law to determine the current. This way you can measure the current whenever you want without having to unsolder a connection.
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Old 4th August 2012, 06:23 PM   #3
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Hi!

If I understand correctly you are using auto bias with a cathode resistor of 880 Ohm.
Why make it adjustable? The point of this bias scheme is that it's automatic and the tube finds its operating point all by itself.

Thomas
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Old 4th August 2012, 06:24 PM   #4
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Old 5th August 2012, 12:23 PM   #5
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Default 300B

for fine adjustment Adjustable think is ideal for when you switch
valve mark differences. On the other hand it could put a jack
to see the current. an issue that was impossible to leave for the delay
buy a sophia electric, when it enters the high tensiion shakes my cone
Speaker TannoyMonitor gold could anyone know where to put.
thanks
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Old 5th August 2012, 01:44 PM   #6
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Hi!

The cathode bias method allows the tube to settle where it 'feels most comfortable'.
The proper way to make current adjustable is with fixed bias. The name is mis lieading. fixed bias means to supply an adjustable bias voltage to the grid and ground the cathode.

Bets regards

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