guitar speaker / was Re: Tube challenge!

Bill Layer blayer at uswest.net
Fri Nov 26 15:34:52 CET 1999


Hello,

>   The problem with Transformers with open secondarys mainly
>comes from the effective resistance that is presented to the
>primary, you effectivly get a massive standing wave problem and
>a tonne of relfections and if its too bad, say good by to the
>thing driving the primary. (wow look ma, I used my transmission
>line/transformer theory I leant at college!!!)

All you need is SOME type of load at the output to prevent this.. I imagine 
even  a 100Ohm resistor would do it.. But it is REALLY important to have 
something if there is the chance that the amp might get signal with no load.

I accidentally touched the input once of an EL84 based amplifier, that had 
an open output. The ball of plasma that engulfed the transformer was truly 
impressive.. looked just like one of those plasma balls that RS sold. The 
room smelled of ozone later. Reminds me of the time I put the glass bowl 
with gold leaf rim in the microwave...


+----------------------------------------------------------+
|      "The" Bill Layer - Frogtown, Minnesota. U.S.A.      |
| Vacuum tubes, Analog, Motorcycles and Other Alternatives |
+----------------------------------------------------------+
+---------------------+  +---------------------------------+
| <blayer at uswest.net> |  | <b.layer at vikingelectronics.com> |
+---------------------+  +---------------------------------+
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