I run them with plate voltages of up to 200V triode connected @ 20mA and so far have not had any issues. Note that I connect G3 to cathode. How long they last at this power level remains to be seen.
Here's a thought: You might want to consider running the D3A as a pentode follower with somewhat lower G2 voltage, output impedance should be lower and linearity possibly better. You could stand G2 on a zener referenced to the cathode..
Here's a thought: You might want to consider running the D3A as a pentode follower with somewhat lower G2 voltage, output impedance should be lower and linearity possibly better. You could stand G2 on a zener referenced to the cathode..
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Hi kevinkr, I must run the plate at 310 V to make sure the grid1 doesn’t go lower than -1 V bias because the grid is at 150 V (DC coupled to previous stage) I will connect G3 to the anode. I want lowest THD at low signal and d3a in pentode makes me fear about noise level as well as distortion , even if the curves looks better (they move with 120Vpp of Vg2). Thanks for the suggestion but I will use another type of pentode with higher g2 max voltage. I want a tube that last 10 years thus I will not permit the grid to be overdriven.
Btw nice website and good looking amplifiers! I will need some help checking out the amp schematic for possible problems before I build it.
Btw nice website and good looking amplifiers! I will need some help checking out the amp schematic for possible problems before I build it.
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Hi, I realize this is old thread, but I feel this is the appropriate place to post this.
I am about to test few triode connected pentodes as a driver in my 211 amp, using Interstage Transformer. I noticed 2 ways to connect a pentode as a triode; G3 to cathode or G3 to anode.
In D3a data shows that this changes grid to cathode capacitance (7.3pf for G3 connected to cathode vs 6.7pf when G3 is connected to anode).
Are there any other considerations to keep in mind when choosing which way to connect G3?
I am about to test few triode connected pentodes as a driver in my 211 amp, using Interstage Transformer. I noticed 2 ways to connect a pentode as a triode; G3 to cathode or G3 to anode.
In D3a data shows that this changes grid to cathode capacitance (7.3pf for G3 connected to cathode vs 6.7pf when G3 is connected to anode).
Are there any other considerations to keep in mind when choosing which way to connect G3?
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