[sdiy] protecting line level inputs

[Cynthia Webster]

on 10/20/04 9:19 AM, Theo at t.hogers at home.nl wrote:

> Diodes from signal to the power rails (both + and - supply).
> This limits the signal voltage to rails+diode drop.
> Usually rails + 0,6V is save, therefore run of the mill 1N4148 are ok.
> And for critical stuff Schottky offers a rails + 0.25V way out.
> 
> HTH
> Theo
> 
> 
> ----- Original Message -----
> From: <modraj at msoe.edu>
> To: <synthdiy at sdiy.org>
> Sent: Wednesday, October 20, 2004 3:33 PM
> Subject: [sdiy] protecting line level inputs
> 
> 
>> SynthDIY:
>> I have determined through experiment that my mixer does not like +/- 15
>> volt spikes (because now it's broken).
>> What's the best way to send signals from prototype circuits (like a random
>> spike generator) to a line level input (zener diodes, pre-amplifier)? What
>> is the maximum +/- voltage that these can handle?
>> - Justin
> 

Hi Justin!

I solved a similar problem the other day with an interesting solution.

I was getting hot spikes from a circuit but wanted to limit the output
from +15V down to a solid + 5 Volt Gate output, I didn't have the right
zener, so I put a 5 volt Voltage Regulator before the output jack and it
worked perfectly, (and added all sorts of short circuit protection in
the process...)  This would not work for an audio signal though :)

Naturally, I'd always thought of voltage Regulators as a constant voltage
level device only, it was a surprise to me that it handled momentary
control voltage swings and rapid pulses with ease!

One of those quickie "what if?" solutions that worked LOL!

Cynthia