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Hi All,
Hi All,
In a recent post http://part15.us/node/1694#comment-5516 I cast aspersions on RCA pin connectors and I thought it might be useful to share some of my experience and “wisdom” regarding the topic of connectors. So here goes….
My experience over many years (oh so many years) has taught me that the RCA audio pin connectors are not reliable. Then, you may ask, why are they used on everything? The answer is “they are cheap”. It has been suggested that gold plated RCA male connectors are good but I ask “what about the jacks? Are they gold plated also?” Don’t misunderstand, these connectors can and do work but they are not the best available and they will fail if there are many plug/unplug cycles.
If asked what in my opinion the are best connectors for audio work I will answer 1/4 inch phone plugs and jacks, especially the products made by Switchcraft. This hundred plus year old design has stood the test of time. I used them in the early days of teleprocessing in our patching and switching frames and never had a failure. I still use them here for patch applications. Another great choice is the XLR series of connectors which are used for professional microphone and audio work.
So, why are these so good compared to the RCA pin types which I disparage? To answer this we need to go back to some basics. Whenever one wants to make a good electrical connection between non-bonded metal contacts a couple of things have to happen. One is that the metal surfaces need to be electrically conductive. All but the noble metals (gold, platinum) are not surface conductive. This is because copper, aluminum, silver, nickel, and so on are corroded by exposure to the oxygen in the air. Oh woe are we, what can be done? One of the techniques employed by designers of connectors and switches is to provide a wiping action when the contacts mate whereby one contact scrapes across another and thereby removes the surface oxidation and this depends on a firm pressure on the mating surfaces. For example, even the RCA pin plugs and jacks use this but this connector quickly loses the spring tension in the female jack required for good wiping action. When you plug a plug into a jack the jack contact wipes the plug contact on the theory that this will scrape away the oxide layer and provide a good contact. It usually works, but when the spring tension on the jack contacts weakens the wiping doesn’t work effectively and the connection fails. I have had connections fail yet some of the signal still gets through yet it sounds weak and distorted. Many times the channel imbalance and distortion at my humble part 15 FM station has been traced to the RCA connectors.
The 1/4 inch phone plugs and jacks and the XLR connectors I mentioned have a large contact area which is efficiently wiped with each insertion and they maintain contact spring tension over thousands of cycles, thus the non existent failure rate (in my experience) for these connectors. One by one, all the RCAs in my world are being replaced.
So, what is a person to do? RCA type plugs and jacks work satisfactorily if there is not a lot of removal and replacement of the connections. If I am designing equipment which will have a lot of activity on the connectors I use the 1/4 phone plugs/jacks and the XLR connectors. They just simply cannot be beat for reliability.
For RF, I use BNC or N connectors. PL259s are not that good for repeated cycling or maintaining impedance. The popular F connectors amaze me that they work at all. The center conductor of these male F plugs is the copper clad steel inner conductor of the coax cable. This is essentially bare copper which oxidizes almost immediately on contact with air. I would not use an F connector in any RF application and have had many service calls from my cable provider tracable to this miserable connector. It is cheap but it is not reliable. Even for hobby use, stick with at least a BNC.
Well, I have given some of my experiences and biases about this and hope it gives some guidance for your hobby pursuits. Don’t avoid any connector system, just know the limitations, especially if repeated disconnect/connect cycles are expected.
Neil
Total posts : 45366I’m glad I found the post about Audio Connectors from Radio8Z, and what he says is indeed the best from experience.
But, we’re stuck with a whole world of low quality connectors and the reason I am all upset is because I never have the right adapters, connectors, cable lengths, despite the fact that I also have been doing this work for decades and the floor is sagging from all the equipment, cables and parts, yet I constantly need to figure out what little junk to order because I still don’t have everything.
Those dinky micro-plugs, the slightly less teensy mini-plugs, and although phone plugs are good like Neil says, they are either stereo or mono, and that can be important.
Add to it the fact some of us also have video gear, with another dozen types of connectors and specialty cables.
Not to mention computer cables, connectors, and the vast array of AC power plugs.
I might quit electronics tonight and walk away into a new life. I hope they have a good website like this one has been.
Total posts : 45366Knowing the limitations of equipment, and in this case connectors, allows one to work within the limitations.
Experience in another venue has taught me how to deal with automotive applications such as the installation of upgrade radios in cars. I haven’t done this in quite a while so things may be different now but back then the most reliable connections were made by soldering wires together and with the introduction of heat shrink tubing this afforded cheap, reliable, and neat appearing connections. Since there is little or no need to disconnect and reconnect the permanent soldered connections are preferred and if disconnection is needed a pair of wire cutters works. There have been some “bad sensor” episodes with family vehicles which turned out to be faulty connections which, as you might have guessed, were solved by soldering things together.
The commonly used barrel connections for modern electronic devices used for power connections work well which surprises me since there is very little tension on the center pin to promote wiping action but the high voltage and current compared to signal lines likely punches through the surface oxide.
In my past life I designed medical diagnostic and life support equipment so I am a bit biased about connection integrity and tend to over do things sometimes but I don’t like to spend a lot of time troubleshooting my hobby equipment so I pay attention to connector quality.
Neil
Total posts : 45366Indeed well soldered connections are many degrees better than depending on low-class small connectors, but special care must be taken with solder work.
Aside from the obvious advice – “don’t burn yourself” – spend a moment thinking about the wire you are soldering….. where is it connected at the other end?
I once detected a broken solder joint in an audio line so I heated the iron and soldered it, being startled with a loud “pop” sound and the smell of burned parts.
At the other end of the wire I had soldered was the input to a 20-Watt Audio Amplifier that was turned on at the time. The point of the solder gun sent too much “zap” down the line and blew out the output transistors in the amp.
I fired myself so there was nobody around to fix the amplifier.
Total posts : 45366I do not find my hatred as strong for the RCA connectors as I do the mini and sub-mini buggers they seem to use on everything these days. At least on the wire end, you can buy quality plugs, but it seems everything built with a mini or sub-mini jack in it has horrible quality parts and they become iffy in a hurry.
But I must say that a key component of any connector is it’s quality. There are SO many horrible, cheaply made Chinese plugs and jacks out there. If I’m doing anything that matters at all, I use Switchcraft plugs and jacks. They’re made in the USA and compared to even an overpriced import are clearly superior. If you’re plugging in and out a lot it’s worth the cost for a decent plug made of quality materials. Especially the 1/4″ units sold by Radio Shack et al. They’re thin metal that breaks easily, the parts rotate allowing terminals to short, jack terminals and springs break off. They’re just horrible.
In my work at the commercial stations I have to repair sports broadcasting equipment — nothing takes a beating more than sports headsets and mixers and interconnecting cables. I keep a healthy supply of Switchcraft connectors in stock for such a purpose. when building a station or anything else, why let all the equipment run the risk of sounding crappy just to save a few bucks on connectors? And yes, I realize that eventually you’ll probably have dozens (if not more) jacks, plugs, connectors, and spending a couple bucks on each instead of a few cents will really add up, but at least it’s over time!
One place not to skimp is on the quality of your interconnets!
Tim in Bovey
Iron Range Country
Total posts : 45366Over on my desk is a detailed purchase order being prepared for connectors and adapters. I am now glad that I have not yet submitted the order, because TiminBovey has said the right thing at the right time and I’m going to switch to Switchcraft!
Come back, if you see this, and tell a good supplier of the Switchcraft line.
Now, thanks to you, I have confidence in the future of mankind in the world.
Total posts : 45366is worth the extra money. This brand and Amphenol were the only connectors I spec’d. for medical equipment. Never had a failure.
One source is Mouser Electronics. All my orders from these folks have been great! I ordered parts on Monday and they are scheduled to be here today (Wednesday). This is typical of their service.
Neil
Total posts : 45366Sadly there are now Amphenol knock-offs. Buyer beware.
Total posts : 45366I get all my Switchcraft items from an outfit called Mid State Distributing. ( https://www.midstatedistributing.com/locations/ ) Used to be S&S Electronics, used to be in Fargo but now they have additional locations. I don’t know anything about them, but I’ve ordered parts from them for probably 30 years. I don’t even know if they sell to the general public. I’ve bought parts for engineering at the various stations I’ve worked for over the years. Sometimes they don’t have what I need in stock, but they get it. The station has a corporate account there and I just call my guy, tell him what I need, and it arrives.
I know you can also get Switchcraft from Allied Electronics, Mouser and Digikey among others.
Hope that helps.
Tim in Bovey
Iron Range Country
Total posts : 45366The old cheapy plug that caused all the problems years ago is still available from Switchcraft. See the outline G and part number 502-3501MX in the Mouser on line catalog:
http://www.mouser.com/catalog/catalogusd/646/1402.pdf
Don’t buy it! If you have any, throw them out. The problem is you need to connect the center conductor by inserting it inside the center pin and then heat the center pin while trying to feed solder to the tip of the pin. Any solder that also flows on the outside of the pin must be completely removed. Solder on the outside increases the pin diameter and deforms the jack center pin causing poor contact after a few plug/unplug cycles. I’ve seen them used to connect shielded cable from board to board in consumer electronics. That’s OK because it never gets unplugged except for repair service.
Otherwise I would trust any of the brands Mouser sells, as long as they have solder terminals and a screw-on handle.
I haven’t had phono plug or jack problems in many years, but I’ll add my name to the list for sub-mini and mini phone plugs and jacks.
Phil
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