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The answer to all your questions

Posted by Russ57 (A) on May 18, 2006 at 12:16:58

In Reply to: while i'm at it, where do i find specs kt-90? posted by radiance on May 17, 2006 at 22:16:43:

Goggle up TDSL...that stands for tube data sheet locator. When you get there you will also notice that they tell you a tubes plate resistance at a given operating point. This info can also be interpolated from the tube's plate curves. It can also be scaled from a known operating point.

Now the bigger question might be what transformer impedance should you use based on the tubes plate resistance? A good rule of thumb for a triode would be about 4 to 5 times. You could go down to around 3 if maximum power was the sole goal and up around 6 if your speakers need more damping. For pentodes plate resistances are so high negative feedback must be used and typically it is best to just go with the advised transformer impedance. However the basic rules are the same...meaning if you use a transformer near the lower end of that advised you get more power but higher distortion.

If any of this isn't clear just ask again. Or if you like, pick a tube and tell me push pull or set and I'll try and walk you through it.

The way described below would tell you when the transformer's impedance matched the tubes impedance and you would never want to operate there.

Russ

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