[sdiy] The annual I/O impedance/protection thread! (revised)

[Stewart Pye]

What signals can be injected into your module is somewhat dependant upon 
the type of connector you use. I've repaired several input stages of 
several mixing desks because people have plugged in the output of a 
power amp (with jack socket outputs) into line inputs of a mixer. We 
don't see it so often now that speakon connectors are more common.

If you use banana sockets it's unlikely anyone will plug in anything 
greater than +/-15V unless they are in a lab, in which case they 
shouldn't be so dumb...
As someone else has mentioned 3.5mm sockets are sometimes used for DC 
and AC plugpacks.

If there is any way to plug the wrong thing in to your module some idiot 
will do it. You can't protect against everything. The main thing is to 
design it so you could patch any socket on your modular to any other 
socket on your modular without letting any smoke out.

A quick list of idiotic connections I've seen, or people have asked me 
to do and I've refused:
Jack socket for composite video right next to a speaker jack socket  - 
to connect a karaoke rack and monitor unit.
Mains plug lead connected to a 100V line PA amplifier that plugs into a 
mains wall socket wired to the PA speakers.
Mains plug-plug lead so you can plug your generator into a wall outlet 
and power up your house when electricity is out.

There's many more but I think I've blocked them out of memory!

Regards,
Stewart.



Justin Owen wrote:
> -----Original Message-----
> From: Neil Johnson [neil.johnson97 at ntlworld.com]
>
>   
>> Well, since you seem unable to provide any *specific* requirements for
>> what you are hoping to protect the outputs from
>>     
>
> You're right - I am completely unable to provide a *specific* list of all the accidental, dumb, absent-minded, drunken, drug-induced, malicious, hilarious and OMFG things that people might do to damage a circuit...
>
> ...but I'm still going to keep building them.
>
> Justin
>
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