Yah... I am pretty familiar with that. In fact, "chained sag" between sections is also the norm. Ostensibly, each resistor in series is both lowering the mean B+ voltage for the next section ("more to the left" on most conventional schematics), but with the use of very small filtering caps ... the net result is RC constants that are pretty small. Seconds.
If the "resistor sound" is what is desired, then just go with a resistor - and heat-sink the thing. If it gets "awfully hot", remember that for a power resistor, +100C to +200C is within its design spec. The ceramic ones ... could get much hotter, and stay that way for decades of hard service. After all, there ain't much removed between a power resistor and a heating coil in a toaster.
GoatGuy
If the "resistor sound" is what is desired, then just go with a resistor - and heat-sink the thing. If it gets "awfully hot", remember that for a power resistor, +100C to +200C is within its design spec. The ceramic ones ... could get much hotter, and stay that way for decades of hard service. After all, there ain't much removed between a power resistor and a heating coil in a toaster.
GoatGuy
Hi all and thanks, my objective is reached! 5W 12V Zener (1N5349) diode (this was value I found at the electronic store near my house). So, setting the current 32mA per tube (El34) I got +B=468V and the sound is perfect to my ears! Living and learning. "Some times you loose several bucks to learn things in practice!!!" 480V to 468 with only one diode working "cold"!
Thanks all!
Hi Guys
The diode is not going to be "cold" but may be cooler than the resistor while playing.
If you are pushing the amp to full output, then you still have the same maximum current through the zener as you had through the resistor. The only difference is that the zener provides a fairly constant voltage drop where the R provides a variable drop.
At the 500mA quoted above, the 12V zener dissipates 6W. The device should heatsinked.
With any component that operates hot, it is important to move the heat out as quickly as possible. Even tubes do not like being hot despite the fact they need the cathode to be hot to function.
The sag in the supply is caused by wiring and component resistances. Enhancing that with further resistance allows the sagged compression effect to occur at a slightly lower power level. On the other hand, using the zeners to provide a constant drop of supply voltage does not change sag at all but does very slightly reduce the maximum power from the amp - maybe 5% if you're lucky, which represents only 0.22db sonically.
Have fun
Kevin O'Connor
The diode is not going to be "cold" but may be cooler than the resistor while playing.
If you are pushing the amp to full output, then you still have the same maximum current through the zener as you had through the resistor. The only difference is that the zener provides a fairly constant voltage drop where the R provides a variable drop.
At the 500mA quoted above, the 12V zener dissipates 6W. The device should heatsinked.
With any component that operates hot, it is important to move the heat out as quickly as possible. Even tubes do not like being hot despite the fact they need the cathode to be hot to function.
The sag in the supply is caused by wiring and component resistances. Enhancing that with further resistance allows the sagged compression effect to occur at a slightly lower power level. On the other hand, using the zeners to provide a constant drop of supply voltage does not change sag at all but does very slightly reduce the maximum power from the amp - maybe 5% if you're lucky, which represents only 0.22db sonically.
Have fun
Kevin O'Connor
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