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Gear / Technical Help => Playback Forum => Topic started by: MattD on April 28, 2004, 10:36:29 AM
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I'm looking for something to physically switch between 2 SPDIF sources. My DAC only has one SPDIF input and I have my DVD player's coax out and my sound card's coax out to contend with.
I just want a simple box with a manual switch so I can eliminate the hassle of unplugging and replugging cables all the time.
Yes, I tried google ... please post a link if you find one.
I suppose I could try something like this (but with RCA connectors):
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-1216 (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-1216)
I'm just not sure if something spec'd for video can pass a 24/96 signal. Rat Shack is good w/ their return policy, so I can give it a whirl.
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Same here! My receiver (formerly Matt's) only has one coax input and I kinda need three... ;D
Armen
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search "digital patchbay". you'll get a bunch of pro audio boxes, I think Fostex makes a relatively cheap one around $130.
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try a 75ohm video switch box, it works great for me. It has 4 RCA video ins and 1 out, that are 75ohm, I've never tried it at 24/96 though, it should work. hope this helps, take it light - discgo
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you could probably build one without too much trouble. I'd think any DPDT switch would work...
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I know I can get such a switch at Radio Shack - how many contacts does it have on the wiring side? None of the pics they have online show the bottom clearly.
I'm thinking 6 contacts is what I'm looking for ... one side of the switch would connect IN1+ and IN1- to OUT+ and OUT- and the other side would connect IN2+ and IN2- to OUT+ and OUT-.
If that's the case, then I can build this thing with some RCA jacks, 75 ohm cable, the DPDT, and a small project box.
If what I described isn't a DPDT, can you clarify exactly what it is?
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Would a homebrew switch have any affect on the signal quality?
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Would a homebrew switch have any affect on the signal quality?
Probably, but not any more than pushing a long run of cable I would think.
Matt, that's definately a DPDT
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Well ... a long run of coax cable attenuates the signal but doesn't otherwise disturb it. In theory at least.
A homebrew switch implies that the coax transmission line must be broken somewhere. Such a disturbance WILL set up reflections in the cable which could smear the digital signal transitions in the cable feed (=> jittery signal).
If you make the switch so that the size of the "broken part" is small relative the shortest wavelength contained in the signal, then the effect can be assumed to be modest.
But you will have capacitive coupling between signals and ground as well as capacitive coupling between the signal conductors themselves.
Video switches are (or at least ought to be) made to minimize reflections, signal loss and coupling. I remember one type of VHF switch using a slider that allowed the two signal feeds to be maybe two inches apart. Modern ones seem to be more compact.
So a VHF (TV) type switch is what you want. If you make it yourself, which I am ALL for, keep the coax shields intact all the way up to the switch terminals (and then some). Use a switch that separates the cable feeds. I think a homemade box would work. Let us know the result!
Jon
PS A google search should probably contain words like Hamradio, VHF, antenna switches, reflections, loss...