Power tube output transformer mismatch

[bepone]

Thanks Bepone and R.G.,

Let me explain: in the design phase, how which diagram will I use for a maximum power and harmonic distortion I want to obtain?
Which parameters, including the Ra-a resistance, vary as the power supplied varies?.

now we are arriving to another graph, and this is anode current versus anode voltage for different screen voltages, with parameter Ugk=0 for all the curves!
max power is when graph is passing through the knee (and bias point) for PP amp like this

Screenshot_20230207-230653__01.jpg

[bepone]

all for class AB1 but we are mostly speaking about this class.
for lower screen voltages, available current Ia is lower like seen on the graph, and power is less..

then for more power we need to increase anode voltage, maybe also screen voltage but not so much, and change little bit Raa curve

[jazzbass]

Thanks Bepone,

I can say that I didn't understand anything and I just hope it's because of the late hour. Tomorrow, with a fresh mind, I'll study the subject well and then, if I still have any doubts (and rest assured they will) I'll bother you again.

A hug, Franco

[Stevem]

To me a simple answer is this.

When you look at ohms law wheel for wattage you se that current and voltage make up the wattage you end up with.

When you apply this to a tube amps and there many different power transformers used you will have different amounts of available voltage and current available to power the output tubes and this is mostly what forms the basis for how much wattage can be produced.

You should go look at tube spec charts and you will clearly see for a given tube the voltage and current levels needed along with the OT impedance to produce a certain output wattage.

Here for example is the data for a 5881 output.
Va is plate voltage.
Ia is plate current.
Zout is the impedance of the output trans.
P is wattage output .

Note that with any power supply that when the voltage is seen to drop down to its least amount that at that point all the current output that the power transformer has available has been used up also.

[jazzbass]

Thanks Bepone,

thanks for your generous help, now it's really clear, at least I think . All this news I had in my head only they were very confused .
Last thing, when I look for tube data, I don't always find their complete characteristics. Can you recommend me a site where the complete data can be found.

A big hug, Franco

[bepone]

No problem if you need to design something new, you are looking those data, openining many datasheets.. also you can do your "own datasheet", because pentode curves are easy to construct , for all the voltages!
Then you need only transfer curve graph , getting complicated more ? Actually is simple, just rotate few graphs and is clear.

Otherwise just take some recommended working point and voltages from the datasheet (there are many for 6L6 and 6V6) and all is fine

[jazzbass]

Thanks Bepone

A Hug, Franco