| scottw |
I have an amp with the ubiquitous PP UL EL34 output with a 4300:4,8,16 OPT.
When you change the output to triode mode, as i understand it, the transformer load is less than ideal. Could you improve the load for triode mode by changing which secondary tap you use? In other words, if you have 8 ohm nominal speakers could you improve the load for the triode strapped EL34 by using the 4 or 16 ohm taps? What about 6 ohm nominal speakers?
Thanks,
Scott |
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| kenpeter |
A loudspeaker can easily vary from 2 to 90 ohms depending what
it is asked to do and wether or not it abuses Zobels to fake a more
stable impedance...
Use whichever tap sounds best, and stop worryin about it. |
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| andyjevans |
Use whichever tap sounds best, and stop worryin about it.>>
Exactly! Could not have put it better. |
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| ray_moth |
For EL34, the 'ideal' P-P load normally recommended in tube manufacturers' data sheets (e.g. Mullard) for push-pull operation is 6.6k for UL and 5k for triode.
Neither of these modes is all that critical (unlike pentode mode) and I doubt if it matters at all if you continue to use the same speaker tap when you change from one to the other. You might possibly notice a slight reduction in both maximum output power and distortion.
My OPT was designed for EL34 in pentode mode, giving a load of 3.5k P-P but I wanted to use triode mode. By using the 4 ohm tap for my 8 ohm speaker, I got 7k P-P, which was 50% higher than recommended for triode mode, but it sounds fine. |
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| scottw |
kenpeter & andyjevans,
Me no worry, just curious. Transformers are still kind of a mysterious "black box" to me.
ray_moth,
Thanks for the details. Looks like the 4.3k ohm OPT will be "close enough" to the spec'd 5k ohm. Guess that's why I've never read about anyone recommending using a different output tap when changing to triode mode.
Thanks,
Scott |
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