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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: Re: Ultrasonic AC for DHT Filament posted by dave slagle on March 6, 2003 at 10:18:52:
I'm quite convinced that the main difference between AC and DC is the amount of stuff in the signal path.One of the drawbacks that some of the DC schemes has is the loss of differential noise rejection that the AC schema has. DHT's have relativly good differential rejection and absolutly no common mode rejection on the filament.
Add to this some of the problems generating clean DC and a whole can of worms becomes apparent.
One thing I want to try is a simple LC filter with common mode choke. This should do a relativly clean job of generating DC without causing high peak currents that can get radiated all through the system both locally and reflected back into the incomming line. The common mode choke should help keep the signal currents where we want them. The residual ripple (which because of the choke input will be only low order harmonics of the line frequency) will be taken care of by having the filament of the DHT configured as if we were using AC heating. Thus we can use the tubes differential rejection to null out the remaining ripple.
I plan on trying this out when I rebuild my 45 amp.
Gary
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Follow Ups
- Yes! - Gary P 03/6/0316:51:00 03/6/03 (1)
- Re: Yes! - dave slagle 18:42:21 03/6/03 (0)
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