Hi, fellows!
Need some help here. Just got a pair of Psvane 6SN7 (HIFI series) for the pre-amplifier stage of my 300B amplifier.
Being naturally curious about the maximum voltage swing I could squeeze out of these, I searched the internet for the manufacturer's datasheet, just because these are recent production '6SN7 style' but could have had some tweaks in production (more up to date materials, better technology, better batch of holly water... whatever) so I just wanted the actual manufacturer's data instead of a 1940s datasheet.
To my amazement the only anode characteristics curves I could find (in a German supplier, not even on the Psvane page) are plotted with positive grid voltages.
Here enters your expertise: why on earth does one need such curves?
in: https://www.tubeampdoctor.com/en/psvane-6sn7-hifi-series-vacuum-tube-single
These are small signal double triodes with very limited power dissipation (3W per triode). If one imagines a point on the graph, say, with 100V anode voltage and +20V on the grid, the current through the valve should be roughly 80mA which corresponds to 8W, enough to melt the anode (not to mention the thin grid wire because I suspect a lot of current will be sinked down to ground through there too).
So, what is the practical use of these curves? And why bunch down the ones that are useful in the lower fifth part of the graph, rendering them unreadable?
Please, show me the light! There must be a reason, right?
Thank you all for your time and patience and but I can't find the answers myself!
Renato
Need some help here. Just got a pair of Psvane 6SN7 (HIFI series) for the pre-amplifier stage of my 300B amplifier.
Being naturally curious about the maximum voltage swing I could squeeze out of these, I searched the internet for the manufacturer's datasheet, just because these are recent production '6SN7 style' but could have had some tweaks in production (more up to date materials, better technology, better batch of holly water... whatever) so I just wanted the actual manufacturer's data instead of a 1940s datasheet.
To my amazement the only anode characteristics curves I could find (in a German supplier, not even on the Psvane page) are plotted with positive grid voltages.
Here enters your expertise: why on earth does one need such curves?
in: https://www.tubeampdoctor.com/en/psvane-6sn7-hifi-series-vacuum-tube-single
These are small signal double triodes with very limited power dissipation (3W per triode). If one imagines a point on the graph, say, with 100V anode voltage and +20V on the grid, the current through the valve should be roughly 80mA which corresponds to 8W, enough to melt the anode (not to mention the thin grid wire because I suspect a lot of current will be sinked down to ground through there too).
So, what is the practical use of these curves? And why bunch down the ones that are useful in the lower fifth part of the graph, rendering them unreadable?
Please, show me the light! There must be a reason, right?
Thank you all for your time and patience and but I can't find the answers myself!
Renato
Because the 6SN7 is widely used as a blocking oscillator or multivibrator. Because both of those uses are regenerative, the positive grid voltage curves are required for the design process. The dotted lines are not plate current. They are the positive grid current when the grid voltage goes positive by the amount indicated on each curve, as a function of the plate voltage. These are also helpful in the design of oscillators.
The plate power dissipation limits on the 6SN7 are time averaged because the limitation is the IR thermal radiation off the plate. Instantaneous power dissipated by the plate over a smaller portion of the cycle can greatly exceed the time averaged 3W limit.
The 6sn7 was originally intended for use a vertical deflection amplifier in a television.
The 6sn7 will do 320 volts peak to peak with 450 volts and a 100K resistor on the plate.
Have a look at the Altec 1570 driver schematic if you are looking for an example of a higher output driver using a 6sn7.
Also do not fear the 450 volts on the plate. That is a running a drive in theater 10 hours a day rating for the 6sn7.
Have a look at the 6BL7 if you need even more voltage.
The 6sn7 will do 320 volts peak to peak with 450 volts and a 100K resistor on the plate.
Have a look at the Altec 1570 driver schematic if you are looking for an example of a higher output driver using a 6sn7.
Also do not fear the 450 volts on the plate. That is a running a drive in theater 10 hours a day rating for the 6sn7.
Have a look at the 6BL7 if you need even more voltage.