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Bottlehead Forum Welcome! Need support, you got it. Or share you ideas and experiences. |
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In Reply to: RE: Beat me to it... posted by Tre' on October 7, 2008 at 17:05:53:
Transformer cores are pretty complex, with many variables that trade off against each other.
Hi-nickel (80% nickel) core material is very expensive, and it saturates easily. For the purposes of argument, you don't want to run it at more than 3000 gauss. Low-nickel (around 50% nickel) is merely expensive and will handle 10,000 gauss, M6 is cheap and will handle 14,000 gauss, and cobalt is extremely expensive but will handle 22,000 gauss. For a transformer design that handles 10 watts in M6, changing to hi nickel gets you a 0.5 watt transformer, low nickel will take 5 watts, and cobalt will handle 25 watts. (The above numbers are conservative approximations; I'm sure someone else will be glad to give you different numbers for maximum gauss!)
But of course you would not use the same coil design for the different materials; the high-permeability nickel cores have greater inductance per turn so you might change the number of turns. A larger core increases the power handling. Changing the number of turns changes the distortion, which is proportional to the core distortion but reduced by the turns squared. A larger core also gives greater inductance so again you might reduce the turns if you can afford the distortion increase. Larger core means bigger wire but longer so copper losses will change.
Those are only a few of the issues that come to mind. Bottom line, a good transformer designer can make sensible compromises and come up with a workable design for any given core material. M6 transformers are usually the most practical; low-nickel will be larger and more expensive for the same performance unless the power is so small that it is not important - such as with line-level and MC stepup transformers.
Incidentally, the airgap makes no difference to the distortion, given the same core and winding. The gap reduces inductance, but the energy that must go into overcoming the hysteresis does not change. Partridge pointed this out first (to the best of my knowledge) in his ground-breaking papers on transformer distortion, some 70 years ago.
The one place I know of where designs can overlap successfully is this: an M6-based airgapped transformer can be stacked with low-nickel laminations that are not air-gapped. The result is a parafeed output transformer with lower distortion, slightly greater power handling, much greater inductance and hence bass extension, and the identical high-frequency performance.
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Follow Ups
- RE: Beat me to it... - Paul Joppa 10/7/0823:17:31 10/7/08 (0)
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