circuit switching

ross21 · 15th July 2011, 02:58 AM

Hi all new here...
I have a ultra low noise pre-amp that am experimenting with and need to switch a capacitor in and out without extra noise. Just switching the one leg of the cap will do.
I dont wish to use a simple on/off toggle switch with leads connected as the leads will act as antenna and induce noise..
Would prefer it as IC based smd or other wise to do the switching .. but this device should not induce noise of any sort.
The other thing is it has to be switched as I need to close up the unit and take it away from any noisy environment.. this is why the switch is needed... as I am testing as to what value of capacitor is needed.
any help on this ??
The unit is running on 7.5 volts and is converted to 12 v and 5 v dual.

ross

sawreyrw · 15th July 2011, 03:24 AM

How do you expect anyone to help you without telling us what the key switch requirements are?

ross21 · 15th July 2011, 05:18 AM

Quote:

Originally Posted by sawreyrw

How do you expect anyone to help you without telling us what the key switch requirements are?

simple switch mA and mV

glennb · 15th July 2011, 06:39 AM

Use a reed relay or a very small PCB relay.

Mooly · 15th July 2011, 07:50 AM

If there is the slightest voltage differential on the capacitor vs the points in the circuit it is being switched into then you will get a "click" noise.

My prefered option would probably be something like a jfet as the switching element.

15th July 2011, 02:58 AM	#1
ross21 diyAudio Member Join Date: Jul 2011	circuit switching Hi all new here... I have a ultra low noise pre-amp that am experimenting with and need to switch a capacitor in and out without extra noise. Just switching the one leg of the cap will do. I dont wish to use a simple on/off toggle switch with leads connected as the leads will act as antenna and induce noise.. Would prefer it as IC based smd or other wise to do the switching .. but this device should not induce noise of any sort. The other thing is it has to be switched as I need to close up the unit and take it away from any noisy environment.. this is why the switch is needed... as I am testing as to what value of capacitor is needed. any help on this ?? The unit is running on 7.5 volts and is converted to 12 v and 5 v dual. ross

15th July 2011, 06:39 AM	#4
glennb diyAudio Member Join Date: May 2004 Location: Melbourne	Use a reed relay or a very small PCB relay. __________________ Glenn.

15th July 2011, 07:50 AM	#5
Mooly diyAudio Member Join Date: Sep 2007	If there is the slightest voltage differential on the capacitor vs the points in the circuit it is being switched into then you will get a "click" noise. My prefered option would probably be something like a jfet as the switching element. __________________ ------------------------------------------------------- *A simulation free zone.* *Design it, build it, test it.*

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15th July 2011, 03:24 AM	#2
sawreyrw diyAudio Member Join Date: Apr 2006 Location: Minnesota	How do you expect anyone to help you without telling us what the key switch requirements are?

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