Good source switcher

MotoMan_Yz400 · 6th March 2008, 09:14 PM

I'm in need to switch video and audio. I know they make manual switchers to do this, but I would like to make my own. I need to switch audio from multi-sources go into my amp, and video from multi sources switched to a output connector. I was thinking of using relays, but dont they have bad noise issues and just dont work well with audio/video? How can I switch reliably (with little to no switching POP) and mantain good quality?

GRollins · 8th March 2008, 01:15 AM

I'm not clear as to what noise issues you mean regarding relays. If you mean the mechanical click as the relay engages or disengages, then yes they make noise. This is easy enough to damp, however. If you're getting a pop through your system when you change inputs, don't blame the relay...there's DC offset at one or more of your inputs. Track down the source of the DC and you'll be able to cure the problem. If nothing else, you can use a capacitor to couple the offending unit to the switching unit. Keep in mind that it will pop regardless of whether you use a relay or any other kind of switch--the DC will still be there.
I don't do much in the way of video, so I'm not in a position to say if there are any special requirements involved. In general, since you're working with high frequencies, I'd suggest good shielding and ground practices.

Grey

abzug · 9th March 2008, 09:34 AM

Video is very high frequency. You should probably use relays with controlled impedance, or the far, far easier option of logic. You can buy say an HDMI switcher for something like $40 or even less. I've taken one apart and it had ICs you can probably find on Digikey or the like (I've since returned it so I don't remember the part number).

paulb · 10th March 2008, 02:45 AM

The requirements for video are different than those for audio. Maxim has some video switching products:
http://www.maxim-ic.com/products/video/
You'd have to know what you were doing to lay out a circuit board for these products. Maybe a commercial product would be more suitable.

raudio1969 · 22nd February 2009, 02:25 AM

I built such a device recently using relays and have not had any problems.

Audio/Video Auto Switch

- Richard

6th March 2008, 09:14 PM	#1
MotoMan_Yz400 diyAudio Member Join Date: May 2007	Good source switcher I'm in need to switch video and audio. I know they make manual switchers to do this, but I would like to make my own. I need to switch audio from multi-sources go into my amp, and video from multi sources switched to a output connector. I was thinking of using relays, but dont they have bad noise issues and just dont work well with audio/video? How can I switch reliably (with little to no switching POP) and mantain good quality?

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8th March 2008, 01:15 AM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	I'm not clear as to what noise issues you mean regarding relays. If you mean the mechanical click as the relay engages or disengages, then yes they make noise. This is easy enough to damp, however. If you're getting a pop through your system when you change inputs, don't blame the relay...there's DC offset at one or more of your inputs. Track down the source of the DC and you'll be able to cure the problem. If nothing else, you can use a capacitor to couple the offending unit to the switching unit. Keep in mind that it will pop regardless of whether you use a relay or any other kind of switch--the DC will still be there. I don't do much in the way of video, so I'm not in a position to say if there are any special requirements involved. In general, since you're working with high frequencies, I'd suggest good shielding and ground practices. Grey

9th March 2008, 09:34 AM	#3
abzug Account Disabled Join Date: Jan 2006 Location: whereisit	Video is very high frequency. You should probably use relays with controlled impedance, or the far, far easier option of logic. You can buy say an HDMI switcher for something like $40 or even less. I've taken one apart and it had ICs you can probably find on Digikey or the like (I've since returned it so I don't remember the part number).

10th March 2008, 02:45 AM	#4
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	The requirements for video are different than those for audio. Maxim has some video switching products: http://www.maxim-ic.com/products/video/ You'd have to know what you were doing to lay out a circuit board for these products. Maybe a commercial product would be more suitable.

22nd February 2009, 02:25 AM	#5
raudio1969 diyAudio Member Join Date: Sep 2007 Location: N38	I built such a device recently using relays and have not had any problems. Audio/Video Auto Switch - Richard