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previous: jason d How does one tell what size filter ... -- 9/12/2000 11:03 PM View Thread

Re: filter chokes

9/13/2000 12:08 AM
dpcoyle
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Re: filter chokes
The goal is to put the ripple many dB down, so you want to design a crossover with a giant L. As the L gets bigger the DC resistance goes up, unless you spend big bucks for larger wire and cores.  
 
DC resistance is generally avoided in power supplies unless you have a special requirement for it. Less than 200 ohms for guitar and 100 for bass, IMO, is groovey.  
 
Single ended, like Champs, etc. need big power supply filtering, compared to push pull, which rejects a lot of power supply noise.  
 
Choice of L depends on how quiet you want hum to be. 5 H works well and 10 H is quite enough in p/p, IMO.  
Current ratings are for what ever is downstream, like, 100 mA for a pair of 6l6's and maybe 20 or 30 for the preamp at 400 v, plus a little for bleeder resistors, etc.  
If you're running a typical amp, p/p, Fender, etc doesn't use a choke for the power tubes, so they only need a tiny current rating to feed the preamp.  
 
The thing about big L is that it, unlike big C, is not hard on a tube rectumfrier, so it can help reject hum in the power supply, if you can afford it and you want that sound.