[analog97]

I was interested to read in the blog the conclusion that JH reached about eliminating the polyswitch in his own DIY project.  To JH, it seemed like a no-brainer and he attributed it to the "non-linear" response imposed on the audio signal due to this device.  Since I am planning to re-do my speaker x-overs, I have 2 questions:

1. Does the polyswitch act as a resistor, and, if so, if one removes it, should a resistor replace it?
2. If the above is accurate, can you remove the polyswitch, measure the inherent resistance, and then use this ohm figure to replace it with a resistor?

Non-random thoughts from a learning newbie!!  Thanks for any guidance.

[hagtech]

I need to investigate the properties of this material(s) for a better understanding.  The basic function is to act like a low value resistor until a current threshold is reached, whereupon it switches to high resistance mode.  It could actually be a thermal trip, rather than current (although related via other parameters).

Therefore, given my limited experience with semiconductor materials, I assumed some nasty nonlinear properties, especially near the threshold point.  There could definately be some parasitic rectification occuring, too.  I remember experiments we once did on the switching properties of cuprous oxide on telephone circuits.  Noisy. 

So my answer would be yes to both questions.  Although I think replacing it with a jumper and not a resistor would lead to the better solution.

Warning!  Removing protection devices puts your drivers at risk!

In my particular case that is ok.  I plan to drive the loudspeakers using a tube/transformer output circuit with no feedback.  Hence, there will never be any dc, it will clip softly, and it doesn't put out that many watts.  I am safe.  Besides, I don't mind if I do blow a driver, as I have the abilities to replace it (in fact, I already booched one of the tweeters).

http://www.circuitprotection.com/radial.asp

jh

[hagtech]

They also post this:

http://www.circuitprotection.com/04Databook/C12_loud_(121-124).pdf

I think there is a lot they are not telling.  The description and operation is greatly simplified.  Would like to see details of the semiconductor / crystal mechanics.

jh