bnc rgbs cables vs rca cables with bnc adapters?

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deezdrama
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bnc rgbs cables vs rca cables with bnc adapters?

Post by deezdrama »

So the cheap monoprice 10ft RGB bnc cables I usually get on amazon seem to have went up in price and now out of stock.... Will there be any signal degredation just throwing some rca to bnc adapters on some component cables, using an audio line for sync?

Just need a couple extra rgb cables to connect a couple rgb muxed consumer crts to a rgb distrobution amp connected to mister/240p.

Thanks
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kitty666cats
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by kitty666cats »

There shouldn't really be any noticeable difference / you can totally use YPbPr+audio cables for RGBHV - though, just keep in mind that SOME RCA cable sets have thinner cabling for the audio lines. I've found that isn't super-common... just look close when you order stuff (or buy at a thrift store) to double-check.

I'd keep an eye out for some decent BNC<->RCA adapters, though. Some of them are seriously so shitty and flimsy
deezdrama
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by deezdrama »

kitty666cats wrote:There shouldn't really be any noticeable difference / you can totally use YPbPr+audio cables for RGBHV - though, just keep in mind that SOME RCA cable sets have thinner cabling for the audio lines. I've found that isn't super-common... just look close when you order stuff (or buy at a thrift store) to double-check.

I'd keep an eye out for some decent BNC<->RCA adapters, though. Some of them are seriously so shitty and flimsy
Awesome...thanks
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NewSchoolBoxer
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by NewSchoolBoxer »

Only thing I want to add is be sure that RCA to BNC connectors are 75 ohm and not 50 ohm. If sales description doesn't say then don't buy. I paid a little more for gold connectors cause shiny is beautiful.

There is some power loss on the extra connection but I seriously doubt it's humanly perceptible. I'm happy to go RCA -> BNC when I don't have a BNC cable.
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Gara
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by Gara »

Dang, it looks like they discontinued the 10ft version.
https://www.monoprice.com/product?p_id=573

I wonder if the other lengths are on their way out as well.
deezdrama
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by deezdrama »

Gara wrote:Dang, it looks like they discontinued the 10ft version.
https://www.monoprice.com/product?p_id=573

I wonder if the other lengths are on their way out as well.
Yeah it sucks, and the price on the other lengths went up on amazon.
I wish I would of ordered a bunch last time I bought one
deezdrama
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by deezdrama »

NewSchoolBoxer wrote:Only thing I want to add is be sure that RCA to BNC connectors are 75 ohm and not 50 ohm. If sales description doesn't say then don't buy. I paid a little more for gold connectors cause shiny is beautiful.

There is some power loss on the extra connection but I seriously doubt it's humanly perceptible. I'm happy to go RCA -> BNC when I don't have a BNC cable.
These are what I ordered. They dont state termination ohms but alot of reviewers said the use with pvms so figured they would be ok

RuiLing 10 Pack RCA Female Plug to BNC Male Jack Adapters Coaxial Connector for CCTV Video https://a.co/d/1o2GFdq
Dochartaigh
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by Dochartaigh »

My first 2 or 3 setups used these exclusively (with BNC adapters), on recommendation of Dak (mod of the Reddit CRT group). No signal loss I could detect on my BVM/PVM's (ran everything through an Extron which does bump up the sync line) and I mostly used the 12' long version:

https://www.amazon.com/gp/product/B008UGEJ94
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NewSchoolBoxer
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by NewSchoolBoxer »

deezdrama wrote:
NewSchoolBoxer wrote:Only thing I want to add is be sure that RCA to BNC connectors are 75 ohm and not 50 ohm. If sales description doesn't say then don't buy. I paid a little more for gold connectors cause shiny is beautiful.

There is some power loss on the extra connection but I seriously doubt it's humanly perceptible. I'm happy to go RCA -> BNC when I don't have a BNC cable.
These are what I ordered. They dont state termination ohms but alot of reviewers said the use with pvms so figured they would be ok

RuiLing 10 Pack RCA Female Plug to BNC Male Jack Adapters Coaxial Connector for CCTV Video https://a.co/d/1o2GFdq
Title and sales description state use for video and they are listed under Audio & Video Connectors & Adapters, so I'd feel comfortable about them being 50 ohm. You're good.

I bought the Monoprice BNC Male to RCA Female Adaptor - Gold Plated since description states 75 ohms. Still two people asking under questions and receiving answers that they will work on 50 ohm equipment. Yeah, if you don't mind a 4% = 0.18 dB power loss that compounds at transmission line length.
Sirotaca
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by Sirotaca »

The impedance is a result of the physical dimensions, so if you know what to look for, you can tell the difference between 50 ohm and 75 ohm BNC connectors visually. 50 ohm connectors have dielectric layers around the connection, whereas 75 ohm connectors have little to no dielectric.

Image

That said, I wouldn't worry about it. RCA connectors are nowhere near 75 ohm impedance anyway (I've seen claims that they're in the neighborhood of 25 ohm), but it's such a short length that it doesn't really seem to matter. Even respected professional AV brands like Extron don't bother using actual 75 ohm BNC connectors half the time. Just make sure your actual cables are 75 ohm impedance and you'll be fine.
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maxtherabbit
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by maxtherabbit »

Sirotaca wrote:RCA connectors are nowhere near 75 ohm impedance anyway
this. worrying about impedance matching on an RCA adapter is comical
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NewSchoolBoxer
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Re: bnc rgbs cables vs rca cables with bnc adapters?

Post by NewSchoolBoxer »

Wait what, 50 ohm adapters have a thicker dielectric? I never knew. The formula has the term [natural log of (radius of outer conductor / radius of inner conductor)] which I thought meant lesser characteristic impedance would have a thinner dielectric.

Altona's AT19062 RCA Component cable I bought is RG-6 coax where having 75 ohm connectors matters. We can make our own RCA cables with coax. But sure I agree every RCA cable sold for video game consoles back in the day and 95% now are not and it's silly to worry about having 50 or 75 ohm in those cases. That 75 and 50 ohm RCA to BNC connectors cost the same, still should buy the correct ones.

Just connecting 75 ohm cable to 50 ohm connector, you take an immediate power loss due to the reflection coefficient = (50 - 75) / (50 + 75) = -0.2. So 1Vp square wave in gets 0.2Vp square wave reflection back and its power is stolen from your video's. Now the further damage from the reflection interference with video is negligible at 4.2-6 MHz Standard Definition with cable length < 3 meters / 9.8 feet. At 480p/576p, you need to be well under 2 meters / 6.6 feet to dodge.

The greater point is you need a high quality signal to begin with for a 0.2 dB or so loss to be perceptible. I can use RG-6 cable for Composite but that's overkill and I don't.
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