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Discussion Starter · #1 ·
I have been comparing Picture Quality between two different component cables and wanted to share the results and generate discussion. I am not mentioning price or online retailers at all.


The issues for me were as follows:


1. Does the use of those BNC-RCA adaptors affect picture Quality?

2. Do the impedance characteristics of a 50 ohm adaptor vs a native 75 ohm BNC termination with no adaptor needed make a difference?

3. Can I see any difference in picture quality between these two component cables that I purchased?


1. The component cabling compared were the well known AV Fusion Component Video Cable RCA-RCA with use of 3 BNC-RCA adaptors to allow connection to the BNC connections native to my Panny42 commercial ED monitor, versus a BNC on one end RCA on the other cabling with Canare terminations ( 75 ohm). Length was 6 feet. DVD Player is a Panny XP30. Mode is progressive scan. DVDs were reviewed, not any HD signal.


2. "Reference" DVDs were the somewhat recent Blue Crush release and an onstage theatrical production dvd called Blast! . I watched the Blue Crush DVD with each interconnect back- to-back. Attention was given to the sunset scenes, pipeline wave scenes, and some of the sand on green nature scenes. The Blast! DVD I have watched 10 times using the AV Fusion Cabling then switching to the Canare BNC-RCA product. Blast! uses incredible color, motion, and lighting schemes throughout that really challenges Black level, color separation etc. red, orange, blue, green, and purple square backdrops on a sectioned stage go through every imaginable lighting combination and costumes change constantly, bringing similar and contrasting costumes, light and backdrop together for evaluation. Viewing was in dark and medium light conditions for both.


3. Result was that the Canare ended BNC-RCA product offered a perceptibly superior result. This is a VERY general statement. I am happy to go into detail in a PM if anyone wants a scene by scene, color by color, rundown.


4. Non-objective totally subjective non-expert statements:

a. The use of a BNC-RCA adaptor may cause a degradtion of PQ, even with a very short 6 foot length.

b. A 75 ohm end should be mated to a 75 ohm cable.

c. Crimped mating of a cable termination to the cable retains 75 ohm impedance better than soldered mating in general, giving less return loss, signal bounce etc.

d. BNC native termination on the commercial Panny may be a superior connection to the RCA option on the consumer version. ( OK- I am now running for cover but I did a bunch of reading on this trying to understand why I might be seeing a difference and this is one offshoot of that reading)


Also, Canare aspects of cabling can be found in many component cabling products not just one. There are additional characteristics of the cabling not discussed here and obviously its important to get all the interconnects hooked up just right. My main point is I think that one less interface is better and therefore it might be worth trying a cabling that doesn't need any adaptors for whatever product someone might have. I understand that not all adaptors are created equal.


Looking forward to learning from any posts to follow.
 

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Quote:
Originally posted by Rysa4
an onstage theatrical production dvd called Blast! .
A fellow corps-head I presume. I hadn't even thought about using Blast! as a reference DVD. Of course not knowing it was out on DVD probably had something to do with that. You're right, it would present a good challenge for image processors and color balances.


Now then, for your actual test results. Can you give any percentages around the PQ differences? Your results imply that the adapters did affect PQ, but how much?
 

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Thanks for sharing your test results with us. I always thought that BNC plugs were designed for a travelling salesman to do presentations and he wont accidentally pull one wire off bec of the lock-in design of BNC. Did you used a 50 cents adapter or Monster gold plated adapter in your test.
 

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BNC plugs are much more than just a won't-pull-out alternative to RCAs. They are a true RF plugs, and can be used in situations where a precise 75 ohm impedence match is critical. For example, all the antennas on most airplanes are connected with BNCs, where a slight mismatch would seriously harm transmitter performance. Also, I once worked around a lot of radio astronomy gear, which works with unbelievably low s/n ratios, and most of that was connected with RG-6 and BNCs. RCAs were originally designed for audio frequencies, and given the vageries of how they are connected, I'm sure the characteristic impedence and shield integrity are all over the place when you try to run RF through them.


Given that video frequencies run well up into low RF, these test results aren't surprising. Regardless of the cable distance, an impedance mismatch from RCA plugs would cause a slight amount of the higher frequency content to be reflected back up the line, resulting in a slight fuzzing of the finer picture details as well as a distinctly non-linear transfer function (i.e. roll-off or peaking) at the plug itself.
 

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Spoffo - I've got the gold plated BNC adaptors from Rat Shack - as recommended by probably a dozen or so people on this board......plugged in to Monster 2's from an XP30 to a panny....


are you suggesting that I am better off going with some new cables with BNC terminations on one end and composite on the other ?


How much is this "impedance mismatch" an effect? very slight? night and day?


......just when I thought I was out........they bring me back in.


Vsapra
 

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Vsapra:


Do you remember the part number of the gold plated connectors/adaptors from rat shack? I can't seem to find them on their web site.


Thanks in advance.
 

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Discussion Starter · #7 ·
Improvement in PQ: Just giving a percentage would also be very subjective. In Blast!, as red shirted performers are flying across red lighting past multi colored background the RCA-RCA interconnect mildly distorted or fuzzed into an almost animated appearance. With BNC-RCA interconnect, the picture remained closer to how I have seen the performance ( three times). In viewing La Nouba ( Cirque Du Soleil), the flourescent green costuming of the Asian girls with the string and European yoyos was simply stunning with the BNC-RCA product over the RCA-RCA AV Fusion with BNC Adaptor. ( My reaction was -Geez I was missing that?) In Blue Crush, Sunset and Pipeline scenes in the background were simply more distinct with the native BNC-RCA interconnect. In general, the improvement was from ( Gosh this is so much better than my 32" Mit TV, to "I am now looking through a Window.")

AS far as the BNC-RCA Adaptor specs, I will get them for you I dont have them in front of me. Very important I wont forget. AS I read a bunch of stuff on the net about this issue I came across the fact that most professional video products and very high end consumer products use BNC plugs and RCA is considered "lower grade" for video (not Audio.) One site did a very interesting review called an "RCA Plug Shootout"-- LOL-- http://www.enjoythemusic.com/magazin...cashootout.htm


An old secrets review stated that the use of adaptors should be avoided if possible


A tech definition manual defined RCA plugs as for use in baseband video without RF Modulation ( see Spoffos Post)


One wild site called wearcam.org (head mounted displays) states that BNC is for high quality professional grade video transmission and RCA is described as " lower quality consumer grade."


Ideally, I would have had multiple products from Monster, Silver Serpent, maybe Audience High Res, AV Fusion, coat hangars, and the brand I got. Two of each, one RCA-RCA using identical adaptors, and the other bnc-RCA for each brand. Unfortunately, I don't have the time or the money, but I sure would read that article.


Heres hoping we all get the best out of our plasmas!!!
 

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VSPRA -


I've never messed with the RCA/BNC adaptors, so I couldn't tell you for sure. It's just that Rysa's results jibe with what I would have expected from my EE days. Where I must use RCAs for video, which is honestly most of the connections in my rack, I use RG 59 or RG 6 coax with compression-fit RCAs. (You put them on with the same compression tool cable guys use.) These have good geommetry and shield integrity and probably come as close to a 75 ohm RCA connecction as you can get. For the long component run to the plasma, I have a set made from RG 59 with these on one end and BNCs on the other, and I'm very happy with the result.
 

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What would 10 feet of component to BNC cable cost?
 

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If I have three 6 foot lengths of RG6 coax, how would I go about making a component cable that had RCA plugs on the DVD end, and BNC plugs on the plasma end?


Is it easy to do? Special tools required? Dumb idea?
 

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Discussion Starter · #12 ·
I wanted to follow up on the question regarding which bnc-rca adaptors I used in my little test--with emphasis on impedance rating. They were from smarthome.com. Product 7809RB. I asked them for the specs. At first they said connectors have no impedance!!! I approached them again. This time they said their supplier was unwilling to reveal where they got the adaptor from or the specs. Since they were 10 for 12.50 ( I got mine free from the online retailer) we can assume that at best we are looking at 50 ohm adaptors. Perhaps not suprising that the native bnc--rca cabling won out for me. Cheers.
 
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