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RCA Sucks - Why Do We Use It?
- Thread starter watchnerd
- Start date
AnalogSteph
Major Contributor
No problem - someone grab a Behringer HD400, she'll be alright.
We can still resort to WD-40 and duct tape later...Mixing these two disparate worlds does in fact bear lots of potential for grief. One follows a philosophy of "floating with unbalanced connections", the other one adheres to "earthed with balanced connections" instead. "Why do I get interference with <studio monitors> on <PC>?" seems to be one of those FAQs that crop up over and over again with remarkable regularity. A PC is mains earth referenced but has unbalanced I/O, so connecting another IEC Class I device is obviously calling for trouble.
How much trouble you're in will depend upon what you need:
1. Unbalanced source --> balanced input. That's relatively easy. Or at least it would if cable manufacturers could be bothered to get their lazy rear ends off the ground and make some proper adapter cables that actually make some use of a balanced input instead of being unbalanced all the way. Seriously, I know of not one pre-made cable that connects signal --> hot and splits unbalanced ground into cold and shield at the unbalanced end. This should mostly work (with some PCB routing related variation), and with an optional ground lift feature, success ratio should be near 100%. Meanwhile, you can also run an unbalanced connection into a line isolator like the trusty HD400 and then continue with balanced cabling - not the cheapest or most ideal option but "plug and play" and working fine in practice.
2. Balanced source --> unbalanced input. That's where it all tends to go haywire. Results will depend upon things like output topology, which in general is not at all transparent to the end user. Those lucky enough to come by a floating output should have few problems assuming the cabling is right (hot --> signal, cold --> ground). With a ground-referenced output you need another cable (hot --> signal, shield --> ground), and if the device you're connecting to is not floating, you're pretty much screwed without a line isolator. And then there are the impedance-balanced outputs, which are much the same (except you can short cold and shield with no ill effects) but are occasionally also found on devices that are not mains earth referenced, like little portable mixers - so getting an XLR mic signal into an unbalanced soundcard input won't be an issue at least.
Then there's the issue of level differences. With 12 dB between -10 dBV and +4 dBu, there's the potential for less than ideal matching and reduced dynamic range. Equipment often provides some flexibility but that may not be enough in all cases.
Incidentally, the classic Pin 1 Problem is not entirely dead and seems to crop up on things like less expensive powered monitors quite regularly. (I suspect that some 5-6" KRKs are affected. As is the pre-AES48 Behringer A500.) Running the input connection over a ribbon cable to the main board seems to be easier production wise. Pin 1 could still have a dedicated return from there to star ground, mind you.
These 4.4 mm things... yeah, that's something I could get behind. For some reason I thought they had just 4 segments, not 5 - my bad.
Unfortunately, establishing new connectors in the slow-moving audio world is akin to some modern-day artist / band becoming as big as the Beatles or David Bowie or other vinyl era icons... they can be as good as they want, it still is not likely to happen.
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watchnerd
Grand Contributor
- Thread Starter
- #143
To their credit, when I tried to order a custom right-angle-XLR-balanced-to-unbalanced-RCA cable from Blue Jeans cable, they basically wouldn't make it until I gave them lots of documentation about the balanced side, which in my case amounted to telling them:
"The PR99 uses fully floating (no ground reference at all) transformer inputs and outputs. This means it can be wired to an unbalanced system (single core cable) by simply using XLR pins 2 & 3. Ground whichever one you want. Any further converting/processing is unnecessary."
OP
watchnerd
Grand Contributor
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Sure has some looping doesn't it?
Both my AEG and EMT turntables have fully-floating transformer balanced outputs and they are so easy to connect to unbalanced inputs. There's something just so right about fully-floating outputs.
S.
My favorite party trick is turning my stereo up to loud, lifting the tonearm, and touching the cartridge terminals. Makes people reflexively cringe, but the balanced circuits absolutely kill that noise (which is common mode).
restorer-john
Grand Contributor
Here is my new cable, a 10' Seismic Audio SATXSW 4x10.
It's the anti-thesis of audiophile, and costs $30 for 10'. I could splurge and get the Blue Jeans version with all Neutrik connectors and Belden / Canare for about $140 for the same length, but that's about as expensive as snake cables get. This Seismic audio version should be sufficient for my Thanksgiving vacation farting around, though, connecting between my RME ADI-2 Pro and Revox PR99.
But here it the real point:
LOOK AT THOSE CONNECTORS
- All the XLR connectors lock
- The TRS connectors aren't locking, but they're so damn long they don't jiggle or come out easily
- They're gigantic compared to RCA connectors, easily able to hold heavy cable weights
- They're interchangeable -- you can uncinch them and convert the type / gender
- You can use the cable as a flail and actually hurt someone instead of merely annoy them
So why do we still have RCA connectors in the 21st century?
Other than being cheap, does RCA offer any technical benefits?
Yeah, I know, standards and format factors die hard, but with digital being the cheap interface of choice now, what's the purpose of cheap analog connectors if it's not for the masses?
At least pricey headphone cables use good connectors....
RCA sucks? I would never have known! I've been in this hobby for 40 years and never knew! RCA connectors have never let me down!
Pure cognitive dissonance?
For a short time my high school electronics class had a fad of leaving charged camera flash capacitors on the floor...
restorer-john
Grand Contributor
Remember the disposable cardboard, built in flash, film cameras? My local camera store used to give me boxes full of them when people dropped them off for developing...
Yep. That's what they were all from. The teacher got a box full of them too.
What's the next trick, putting paper clips in the power points or charging up a mains rated capacitor and chucking it to your party guests to play hot potato?
Can I get on your guest list? Pleeeeaaase?
I can remember an avatar on this forum showing a young blonde kid about to prod a power outlet. I could be mistaken but I think it was @SIY's.
Yep, that was mine.
I once worked in the repair shop at Profoto. Their flashes delivered 2400 joules at 1 kV. You did not touch the fully charged capacitor banks and live, or at least that was the theory. Nobody had been foolish or unfortunate enough to do so.
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Try playing with the starting transformers for large industrial gas fired boilers. Skillfully arcing the 10KV plus power thru the air could be impressive. Definitely more so than the charged caps my electronics tech instructor would charge, toss your way and say heads up catch this.
