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In Reply to: RE: Choke inductance - lower currents? posted by vbenonisen on March 02, 2012 at 14:22:43
hey-Hey!!!,
At 100 mA of DC you'll be well into the largely constant inductance zone. You don't say how many volts you'll be applying to it though; with input service the AC component will not be small. I can give you a point at which that particular choke served well. 400-0-400 applied full wave with a DC component of ~170 mA. It stood this w/o complaint like buzzing or saturation. The output DC matched PSUDii well, indicating it was still behaving like a 10 Hy choke.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Follow Ups:
Thanks! Good to know. Was a bit worried about mechanical noises, but IŽll guess the monstersized choke can handle it.
I have just one more question regarding LC-supplys:
When used as a power supply for the output stage of a single ended amplifier the current in the output transformer swings up and down with the music around the bias point, and the minimum current is a little difficult to pinpoint precisely. Do I just draw the loadline of the output tube and use that as a reference?
Vidar
Vidar,
A SE topology will run class A. You won't see enough current swing to be concerned with your choke inductance range.Draw your load line on the published plate curves. Keep in mind that a Choke input will drop your B+ around 10% down stream.
Stuben
Hi!
Those current swings due to the music signal will be mostly supplied by the last filter cap in your supply, so your input choke will not see them, at least only to a much lesser degree.
I'd recommend a bleeder resistor which ideally ensures critical current draw at all conditions even if the output tube fails and does not draw current. Depending on the voltage this might require to dissipate an unpleasantly high power in the bleeder. In that case make sure your caps have a voltage rating which is able to cover such falut conditions in which the voltage rises by up to 50%.
I'd rather get a choke which is speced for the applicatoin than getting one with much higher current and hoping it will not procude noise
Best regards
Thomas
Hello!
Thank you for your answer. Good to know that the input choke doesnŽt need to "swing" as much as I first thought.
If I follow your recommendations my 300B monoblocks probably need bleeders with a current draw of around 40-50 mA and that will indeed produce a lot of heat. I probably make separate power supplies for the input and driver stage to get better flexibility when experimenting, AND to reduce the risk of destroying everything if something goes wrong.
Regards, Vidar
Vidar,The critical current, in mA., roughly = V/L. When a 10 H. 1st inductor is used, a 10 KOhm bleeder is correct. You take it from there.
Eli D.
Edits: 03/03/12
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