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newbie question about choke

5/28/2000 8:34 AM
newbie question about choke
In a Bassman-style circuit (5F6A) could the choke be removed ore replaced by other components?  
Thanks in advance
5/28/2000 12:08 PM
Carl Z

If you completely remove the choke your screen will be running at the same voltage as the plates. Not good!  
The combination of the choke and the caps creates an LC filter network called a PI filter. Very good at smoothing out the ripple in your rectified DC. If you don't use a choke here you're going to get a substantial increase in power supply noise.  
You can replace the choke with a 300 ohm(ballpark value) resistor rated at around 10 watts but as you start to run the amp harder you're going to drop a lot of voltage across it and you'll lose headroom. Also, because of the reduced ripple reduction, wow does that sound redundant, you'll need more input filtration which may overstress the rectifier tube and cause it to fail.  
So I guess the answer is no, unless you're prepared to completely redesign the power supply.  
Carl Z  
5/28/2000 5:28 PM

Many thanks for your explaination. Actually I am considering to rebuild a Sovtek Mig-50 head (no circuit board inside) to 5F6A design. I noticed that Sovtek design has no choke but has huge filter caps. I have to decide between Sovtek and Bassman supply design, considering that in any case I'll use a SS rectifier.  
Any suggestion will be appreciated.
5/29/2000 10:30 PM
Don Symes

Grab a copy of Duncan's power supply designer software at  
It will help you tremendously.

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