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In Reply to: RE: combination resistor/choke anode load posted by hennfarm on May 21, 2012 at 19:55:11
Why would you want to do that?
Follow Ups:
Invalid entry, that did not answer my question
Detail as to why you do things or want to do things are important in order for someone to answer your question.
Personally I think it's a silly idea and there are better ways to do it. Does that answer your question?
I assume hennfarm is talking about an anode choke load. Probably common cathode bias...B+ rail is the same for driver and output tube.
I have the same issue....
Choke for AC impedance, but the DCR of the choke is too low so cathode/anode current must be limited.
Can't be done by the cathode resistor, that has to set the bias.
If it is not done with a resistor in series with the choke, then how better to do it?
robert
Kellymon, that is exactly what I am up against. Thank you everyone for your replies, and Stephen, my apology my caffinated am mania.
It could also be in the cathode of a diff pair and a resistor is needed to bias the pair properly. Dave Slagle's post gave the options for the anode scenario.
I would prefer to use the resistor in the B+to drop the voltage to the choke loaded stage followed by a cap and then a normal choke loaded stage. Unless the 2 stages are DC coupled and then the option may be to have the resistor in series with the choke.
cheers,
Stephen
Interesting suggestion Stephan...basically you would add another pi filter stage?
For example, if the existing filter was already LCLC you would add another stage for the driver only? So the B+ to the driver would look like Rectifier> cLCLCRCL Driver Anode?
What would you suggest to hennfarm to use as a -3db rolloff point so he can determine a cap value?
robert
If there was room, funds or the parts lying about, I would use a separate supply for the driver but otherwise yes to your conclusion. But for some other people and other circuits, who knows, the series R and L might be fine. We all have prejudices and without trying out everyone's ideas, how can anyone say the have "the answer" and then only for that circuit or that person.I ended up with this exact situation in one of my phono stages but the choke loaded stage was the output. I've since rejigged it and the high value dropper is now a long tail in a DC coupled diff pair output.
Every circuit is different and without all the details of whole circuit, recommendations would be pointless which brings us all the way back to my original question ;) I tend not to calculate stuff but use LTSPICE as it can give a better overall picture.
cheers,
Stephen
Edits: 05/24/12
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