Valve anode voltage.

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pre65
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#1 Valve anode voltage.

Post by pre65 »

I'm embarrassed to ask this question, but perhaps others might not know either.

I tried Google, and looked in MJ's book, but can't seem to find the answer.

When a valve data sheet lists recommended settings, is the anode voltage inclusive, or exclusive of the cathode voltage ?

So, if anode V = 135V, and cathode is 9V, what should the voltage at the anode be, 135V or 144V ?
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Nick
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#2 Re: Valve anode voltage.

Post by Nick »

When a valve data sheet lists recommended settings, is the anode voltage inclusive, or exclusive of the cathode voltage ?
Repeat after me, the valve only knows the voltage at its pins :-)

Its the potential difference between the cathode pin and the anode pin.
So, if anode V = 135V, and cathode is 9V, what should the voltage at the anode be, 135V or 144V ?
I don't know how to parse that question so I can't give the correct answer.

I think you mean 144v. Remember there is no real 0v
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#3 Re: Valve anode voltage.

Post by IslandPink »

Just to expand on what Nick has said, the valve datasheet is going to show anode voltages, and the grid lines ( for A1 ) will be labelled in negative volts. So it's all assuming cathode = 0.
Hence in the example you've given, grid is likely to be -9V, so if you use auto-bias, then as you say, cathode will be +9 , grid 0V, and anode 144V relative to the amp earth.
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Nick
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#4 Re: Valve anode voltage.

Post by Nick »

Hence in the example you've given, grid is likely to be -9V, so if you use auto-bias, then as you say, cathode will be +9 , grid 0V, and anode 144V relative to the amp earth.
And the valve will see Anode +135v, Grid -9v, Cathode 0v. Valve voltages normally assume the cathode is the voltage reference point. Such a standard over the years that they never thought it was worth saying.
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Paul Barker
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#5 Re: Valve anode voltage.

Post by Paul Barker »

Nick wrote: Fri Jun 12, 2020 4:11 pm
Hence in the example you've given, grid is likely to be -9V, so if you use auto-bias, then as you say, cathode will be +9 , grid 0V, and anode 144V relative to the amp earth.
And the valve will see Anode +135v, Grid -9v, Cathode 0v. Valve voltages normally assume the cathode is the voltage reference point. Such a standard over the years that they never thought it was worth saying.
When it does have to be said, it’s like pulling teeth.
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Paul Barker
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#6 Re: Valve anode voltage.

Post by Paul Barker »

I think the problem is majority of people don’t construct an internal view by getting inside the world of a valve so it’s not as clear as day thought it ought to be. A bit like why differently conceived members of human race can’t parallel park or play the piano.
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