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previous: RJH Can someone provide a usable formul... -- 2/23/1999 8:59 AM View Thread

Re: Formula for output trans match?

2/23/1999 10:11 AM
Re: Formula for output trans match?
There really isn't a simple formula to determine what load impedance is suitable for which tubes. These things are usually determined by the tube designer/manufacturer by actual testing & measuring. It's rather complex and results vary with tube characteristics, operating voltages, power output and distortion characteristics. There isn't one perfect load for each tube, either. Everything's a compromise.  
There is a way to determine a load graphically (along with some simple equations) using the manufacturer's published plate curves, and for instance the method is shown in the front pages of an RCA tube manual. It will take a while to go through this method, but it does help and I think it's worthwhile to get a feel for what's going on.  
Since most of the proper matches have long since been determined, usable loads are tabulated in tube manuals and even transformer manufacturers' catalogs.  
It's not a dumb question, and it's damn frustrating to grasp the operating characteristics of vacuum tubes. They look simple, but they are actually complex multi-dimensional devices. I've only scratched the surface myself and obtained a somewhat usable working knowledge that gets me by. There's still an awful lot I'd like to understand.  
Keep up your interest and don't get frustrated.