Nearly a DIY disaster

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activexp

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Nearly a DIY disaster
« on: 29 Nov 2010, 04:36 pm »
I made some changes to the XO in my Wilmslow Audio 'Nemesis' clones and was quite satisfied with the end result, cured a midrange honk. All good so far.



After an extended listening session I went to switch off my NAD C325BEE amp
and was shocked to find that it was extremely hot. It always gets a little
warm on the right side of the case but this was the entire unit. There's a
turntable sat on top and that was cooking too.

Obviously it was drawing high current for some reason so I put a meter
across the 'Nemesis' and was surprised at the result of 0.4 ohms! At first I
couldn't see anything wrong with the XO as there are only 3 components, an
inductor in series with the woofer, and on the tweeter, a parallel inductor
and a series capacitor. Then I noticed that I'd put the capacitor after the
inductor. When I rearranged the layout with the cap before the coil, all was
well. 6.5 ohms!

Credit must go to the stability of the NAD amp and I reckon I was lucky not
to have blown it!

Another lesson learnt.