Quantcast S-video audio switcher recommendation? - digitalFAQ Forum
  #1  
01-29-2021, 02:35 AM
latreche34 latreche34 is offline
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I need a S-Video switcher for at least 3 sources (S-VHS, ED-Beta and Hi8), Looking for an active device (non mechanical switcher that uses an IC instead of physical buttons), There are a lot out there but one US company stood out, it's called Shinybow and was wondering if anyone used their products before? It's cheaper on B&H. Here is another box, I don't know what's the difference.
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  #2  
01-29-2021, 07:33 AM
dpalomaki dpalomaki is offline
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I've not used one, but the difference I see immediately is that the SB-5450M is listed as rack mount, size and weight are thus a bit different, and is comes in an arguably more professional looking black case for about $50 more. B and H lists both models.

Two issues I note are:
- it does not convert composite in to s-video put or visversa. (Not necessarily an issue.)
- the bandwidth of -3dB at 100 mHz is based on a 200 mV signal. Analog video is 1 v Peak to Peak including sync. That looks like it might reflect a slew rate limit on internals; that may or may not be an issue for your uses.
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01-29-2021, 12:21 PM
latreche34 latreche34 is offline
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No I don't need composite conversion, Just S-Video switching. Yeah not sure about the millivolt, but I just assume it switches the signal in full voltage since there is no processing going on.

Right now I'm using a S-Video coupler and S-Video cables to switch between them to avoid damaging the S-Video sockets on the devices themselves but I got tired of doing it, I just want something that can do that for me without loosing signal or introducing noise since this is going to be used for the capturing workflow.
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  #4  
01-29-2021, 02:08 PM
dpalomaki dpalomaki is offline
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Quote:
...but I just assume it switches the signal in full voltage since there is no processing going on.

Read more: http://www.digitalfaq.com/forum/video-workflows/11450-video-audio-switcher.html#ixzz6kxwt4f4M
If it is all electronic (no mechanical switches) it probably amounts to a unity gain amplifier (at low frequencies) that is electronically switched on/off. In that case there is still processing going on so it will add what ever internal amplifier noise and cross talk there is to the signal, and it will have high frequency roll off (specified -3 dB at 100 mHz) for 200 mV signal amplitude. The high frequency roll-off and input limitation implies with the SB-5450.

I read the spec to mean that an 100 mHz input signal of 200 mV or less will have a undistorted output that is down -3 dB at the output. Inputs in excess of 200 mV may be distorted. If this is a slew rate driven limitation than it implies a 50 mHz signal input of 400 mV could be passed cleanly, and a 25 mHz signal input of 800 mV cold pass cleanly.

The published frequency response, S/N, and cross talk specifications do appear to be adequate for SD video.

FWIW: I recall some past threads where folks have created a patch panels for changing connections while saving wear on the gear I/O jacks. I've use a simple 4-input mechanical selector switch such as the Sony SB-V30S
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01-29-2021, 07:24 PM
latreche34 latreche34 is offline
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If processing involved then this is not what I'm looking for, I was thinking the switching is done with solid state gateways instead of mechanical switches or elctro-mechanical relays which suffer from signal leak and noise exposure, I guess I will have to stick to my S-Video coupler then or find another switcher that can do the solid state switching instead of mechanical or electro-mechanical via a relay.
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01-30-2021, 07:56 AM
dpalomaki dpalomaki is offline
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The specs indicate signal leakage between inputs of -55 dB (0.13%), and noise -50 dB (0.3%) in the SD video range.

Because this is handling video signals, which are at radio frequencies, it should preserve the 75 ohm input/output impedance common to analog video systems, and thus needs amplifiers to provide the necessary buffers between input and output while maintaining unity gain on pass through signals.

The as with the electronic system, cross talk and environmental noise pick-up of mechanical switch systems would depend on their layout and construction including shielding. What is lost is the noise and distortion introduced by the active components (e.g., ICs, transistors, etc).

The good (??) news is that most SD analog video sources of current interest, such as VHS and Video8 tapes have a fairly high noise floor and limited bandwidth to begin with so the above limitations may not be at an objectionable level. Cross talk issues can be managed by turning the unwanted source off.

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  #7  
02-01-2021, 02:18 PM
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You don't want this. It add processing.
In practice, it also adds lots of noise, I've never found an s-video switcher that was any good.

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