Input selector switching

APK · 9th January 2009, 12:25 PM

Hi All

I am looking to build a 6 input selector and was enquiring if theseHere Vishay DG542 analogue digital switches compare with relay switching.

Also I note that in some designs I have looked at a 100K resistor is between the input signal and ground (Dantimax Input1) can someone advise why?

Regards
Tony

AndrewT · 9th January 2009, 12:33 PM

the 6way 2pole rotary switches do a good job.
Cheap ones are available from Maplin, Rapid, etc.

Most inputs have a DC blocking capacitor.
Leakage through this capacitor can leave a DC voltage on the RCA input pin.
Similarly the source can also have this leakage induced DC voltage on the output pin.
Adding a high value resistor from pin to Signal Ground shorts the leakage to Ground.
This allows interconnects to pugged and unplugged hot. But this is bad practice, we all know we should switch off before changing the interconnects.

Once both output and input are interconnected the two resistors have no further advantage. In fact, some manufacturers claim that their removal improves sound quality by increasing the loading impedance seen by the source.

APK · 9th January 2009, 02:05 PM

Andrew thanks for the info

I should have been more specific about the selector, I intend to use a Microcontroller to handle the switching via IR so I need some form of electrical switch / relay

9th January 2009, 12:25 PM	#1
APK diyAudio Member Join Date: Jan 2005 Location: NW	Input selector switching Hi All I am looking to build a 6 input selector and was enquiring if theseHere Vishay DG542 analogue digital switches compare with relay switching. Also I note that in some designs I have looked at a 100K resistor is between the input signal and ground (Dantimax Input1) can someone advise why? Regards Tony

9th January 2009, 12:33 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	the 6way 2pole rotary switches do a good job. Cheap ones are available from Maplin, Rapid, etc. Most inputs have a DC blocking capacitor. Leakage through this capacitor can leave a DC voltage on the RCA input pin. Similarly the source can also have this leakage induced DC voltage on the output pin. Adding a high value resistor from pin to Signal Ground shorts the leakage to Ground. This allows interconnects to pugged and unplugged hot. But this is bad practice, we all know we should switch off before changing the interconnects. Once both output and input are interconnected the two resistors have no further advantage. In fact, some manufacturers claim that their removal improves sound quality by increasing the loading impedance seen by the source. __________________ regards Andrew T.

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9th January 2009, 02:05 PM	#3
APK diyAudio Member Join Date: Jan 2005 Location: NW	Andrew thanks for the info I should have been more specific about the selector, I intend to use a Microcontroller to handle the switching via IR so I need some form of electrical switch / relay

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