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In Reply to: End Of Zen schematic posted by Tom §. on October 29, 2001 at 07:29:32:
I have a couple hammond chokes hanging here would the
Hammond 154E 20H, 20ma, 1666 ohms, 300VDC; be a reasonable substitute for the 1.8K ohms in the power supply? Thanks,
Nope. The current draw for that part is about 70mil with the 6N1P installed or 90mil with the 6H30Pi. In both cases the current draw exceeds the current rating of the choke. If I were to put a choke in the power supply, I'd replace the 510ohm resistor with a hammond 159M. This would provide about a 26dB reduction in the power supply ripple.
Besides knowing what the draw is on the power supply, how does the resistance of a choke come into play and does it have anything to do with the 510 ohm resistance value you had spec'd in the supply? Are there any rules for why you have replaced the resistor that is earlier in the chain (of the power supply) rather than later in the chain (the two 1.8K ohm resistors)?
159M 15H, 100ma, 256 ohms, 500VDC
How did you figure that out?
Well, I know what the current draw is because I measured it. I was also able to accurately simulate the circuit in duncan amps PSU2. This let me substitute in a choke and observe what what would happen if everything else in the circuit stayed the same.
how does the resistance of a choke come into play
The static resistance of the choke acts like a normal drop down resistor when it passes DC current. It will reduce the output voltage if you use a choke with higher DC resistance.
does it have anything to do with the 510 ohm resistance value you had spec'd in the supply?
I wanted to get the DC resistance value as close as possible to that value. The reason is so that the DC voltage at the output will not change a whole lot and the operating points of the tubes stay close to where they were before.
Are there any rules for why you have replaced the resistor that is earlier in the chain
No rules. Just a preference. You would have to buy 2 chokes if you were to replace the 1.8K resistor. You only need to buy one choke if you were to replace the 510 ohm resistor and you would still get the same reduction in ripple. Just being cost effective and effecient with real estate in the box.
Thanks, do you know how and where I can purchase the duncan amps PSU2 program to simulate your circuit and learn more? That way I can figure out how much of a difference in the DC voltage really does occur since the resistance of the 159M choke is 256 ohms at 100mA. I gather the DC voltage probably increases slightly but not by much due to the decreased resistance of the choke and the current the circuit is sitting at i.e. 70 or 90mA depending on the tube chosen.
The 1.8K resistor actually draws 35mil with the 6N1P and 45mil with the 6H30Pi. The current draws I gave earlier are for the 510 ohm resistor. Although, the 154E still isn't properly rated for replacement of the 1.8K resistor.
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