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RCA interconnects; why coax construction and not simple 2 wire?

I've never picked up light aircraft and there's a municipal strip nearby. But the military stuff? I know from operating it myself it can punch out some serious power when you need it.....which I'm guessing it might be.

Now that I think about it, it might be an HF call identifier. Kind of sounds like it. Each of our aircraft has a distinct one and "tones it out" first on highest power when we would use HF. It's how the HF ground stations would identify us by tail numbers before we even spoke....
RF energy and radios have some interesting and strange behavior if not calibrated properly and tuned. I am going to assume that military gear is working to a legal standard and would not have issues like this. Curious, what turntable and amp are you using?
 
I get that line levels are low strength signal and the shielding of an outer braid helps reject external "noise" sources like RF and EMI, but is it really that much of a problem if a simple two wire cord is used? Would they really be at risk of picking up RF/EMI in a home audio scenario?
Yes and this is very easy to verify, but only if the screen is connected correctly to the connected gear meaning the screen should go all around the middle conductor and the screen must be connected to the chassis and or audio ground (common) of the circuit on both ends of the cable.
I sometimes see 2 wire + shield where the shield is connected on one side only but these simply don't shield and the internal wire for the audio ground is higher impedance than the shield.

One could prevent RF by twisting the wires (without shield) but again... this does not help for leakage currents (and ground loops).

It is important that the common wire (audio ground) is very low impedance/ohmic because when it has a somewhat higher resistance a 'leakage current' flowing in it will cause a voltage drop across it an thus make its entrance in the audio path.
Shields are MUCH lower impedance than a single wire so that helps as well and not just the shielding part.

It is an ancient relic (the RCA connector) and better connections exist like the BNC connector on the scope which is shown in your avatar and balanced (mini)XLR for instance and even the Pentaconn (4.4mm TRRRS jack connector).
The RCA connector is there and doesn't seem to go away. If only the designers had been smart enough to ensure the shield would make and break before the center pin does.
Such RCA connectors do exist but are rare and expensive. Anyone that ever inserted or pulled an RCA connector from a working system knows why the connector doesn't have a really smart design. A shorter center pin or deeper contact in the socket would have been welcome.

When you want to make a cable just use a coax type cable and connect the shield to both sides of the cable. Make sure the shield is low impedance and don't make them any longer than needed. This helps keep the shield impedance down.
Use all metal RCA connectors that have a decent 'clamp' to the RCA sockets.
 
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RF energy and radios have some interesting and strange behavior if not calibrated properly and tuned. I am going to assume that military gear is working to a legal standard and would not have issues like this. Curious, what turntable and amp are you using?
I use two turntables. Both Duals. a 1249 and a 1229Q. ADC XLM MKIII cart (MI) on the 1249 and a Denon DL110 (HOMC) on the 1229Q. I'm drawn to the Duals because of their all mechanical mechanisms.

fr_4872b.jpg


Rebuilt/serviced them myself and built the plinths myself too. I'm a handy guy when I want to be. ;)

Both are using their own ART Phono Preamp Pro.

Preamps feed into a Sansui 8080DB (repaired and restored by me, was a fun learning project) via the aux in.

Works fine for my purposes.
 
I use two turntables. Both Duals. a 1249 and a 1229Q. ADC XLM MKIII cart (MI) on the 1249 and a Denon DL110 (HOMC) on the 1229Q. I'm drawn to the Duals because of their all mechanical mechanisms.

View attachment 422447

Both are using their own ART Phono Preamp Pro.

Preamps feed into a Sansui 8080DB (repaired and restored by me, was a fun learning project) via the aux in.

Works fine for my purposes.
IC. One should expect RF to not be picked up by such gear but it happens. Does it happen with both turntables?
 
IC. One should expect RF to not be picked up by such gear but it happens. Does it happen with both turntables?
I honestly can't remember. It's that infrequent. For some reason I think it's the 1229Q, but that might just be because the idler table tends to get a little more play time than the belt drive 1249....
 
I honestly can't remember. It's that infrequent. For some reason I think it's the 1229Q, but that might just be because the idler table tends to get a little more play time than the belt drive 1249....
IC. Off topic but why the idler table rather than the belt drive one? Idlers have more W&F I think.
 
My experience with RCA connectors goes back to the 1950s when my parents bought an RCA Victor 45 RPM record changer to plug into the "phono jack" of our 12" B&W TV. Even back then, the cable was shielded. The only unshielded cables with RCA plugs I encountered during my many years running an "authorized service" audio repair shop were attached to the speakers of cheap stereo systems from the likes of Lloyds and Soundesign.
 
My experience with RCA connectors goes back to the 1950s when my parents bought an RCA Victor 45 RPM record changer to plug into the "phono jack" of our 12" B&W TV. Even back then, the cable was shielded. The only unshielded cables with RCA plugs I encountered during my many years running an "authorized service" audio repair shop were attached to the speakers of cheap stereo systems from the likes of Lloyds and Soundesign.
I'm the same on the RCA stuff. I've seen twisted and braided pair RCAs but I never used them.
 
IC. Off topic but why the idler table rather than the belt drive one? Idlers have more W&F I think.
my idler is pretty modified for a Dual:

fr_4449.jpg


CNC parts, graphite center bearing, etc. I'm a tinkerer and I like to get as much as I can out of something I own. It's just my thing. :)

As it is, it matches the stock numbers for the belt drive 1249. It will put down W&F in the 0.04 range. The 1249 is also quite modified and gets better numbers than the Dual advertised for it, usually in the .002-0.03 range. RPM is as stable as you can get for a non quartz locked unit. Both are in the 0.2% variance range for rpm.

But it's not the W&F numbers that make the diff for me. Those numbers are so low that I can't perceive them anyways.

The idler probably gets a little more time because of the Denon. It's a little "sharper" than the ADC in back to back comparo's. Or maybe the word is "detailed". Dunno for sure, it's my subjective impression.

The ADC is a 1970's cart with a new elliptical stylus and the Denon is brand new, both done 2 years ago at roughly the same time.

But to be honest, you have to back to back them to hear the minute diff between them and even then, I can listen to either one and be totally satisfied.
 
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my idler is pretty modified for a Dual:

View attachment 422448

CNC parts, graphite center bearing, etc.

As it is, it matches the stock numbers for the belt drive 1249. It will put down W&F in the 0.04 range. The 1249 is also quite modified and gets better numbers than the Dual advertised for it, usually in teh .002-0.003 range. RPM is as stable as you can get for a non quartz locked unit. Both are in the 0.2% variance range for rpm.

The idler probably gets a little more time because of the Denon. It's a little "sharper" than the ADC in back to back comparo's. The ADC is a 1970's cart with a new elliptical stylus and the Denon is brand new, both done 2 years ago at roughly the same time.

But to be honest, you have to back to back them to hear the minute diff between them and even then, I can listen to either one and be totally satisfied.
Very cool. Taking MODing to the next level.
 
I subscribe to:

If its worth doing, it's worth doing right.

Military thing in me I guess: there are no half measures. All in or all out.

;)
Off topic again but what did you do in Flight OPs? I always like to read and hear about such experiences.
 
Off topic again but what did you do in Flight OPs? I always like to read and hear about such experiences.
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Started on the CH113 Labrador, was one of the initial cadre to bring the CH149 Cormorant online.

413 Sqn Greenwood, 442 Sqn Comox, 424 Trenton, 103 Sqn Gander, then 413 Sqn Greenwood again. Operator to Chief flight instructor. Master Warrant Officer at the end.

Some other flight ops in there I'd rather not discuss (or remember).

30 years operations. Now retired. Broken and beaten body, few squirrels are out of their cages and chewing on the wiring. Doctors finally pulled me off the line and medically retired me because i was like that punch drunk fighter: just kept crawling back into the ring.

wouldn't give up the experiences for a million bucks....but wouldn't do them again for million bucks....
 
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View attachment 422462

413 Sqn Greenwood, 442 Sqn Comox, 103 Sqn Gander, then 412 Sqn Greenwood again.

Did some Griffin time too, but I'd rather just forget that....worse memories than even the bad parts of SAR.
Going off memory that is a Cormorant? Very intriguing! Lots of very happy people have seen that one coming to the rescue I bet. Thanks for sharing. :D
 
I'm no expert, but from what I remember reading is the twist is generally not desirable as it makes the length longer overall, which increases impedance, which degrades the line level signal. Don't quote me on that though. As I mentioned, I'm certainly no expert.

We do it on data bus wiring, but that's likely a bit different principle than audio cabling as that's shielding communication data between things like ADU's, radios, FCU's, etc.....IE: digital information, not analog.
Data wiring twisted pair works on balanced transmission, just as it does for analogue audio. It works because the transmitter and receiver are both balanced and differential, so only respond to the difference in voltage between the two wires. External interference induces equally in the two wires, so cancels in the receiver. Balanced audio will work fine over unscreened twisted pairs for line levels, and not over long distances whereas low level microphone signals still need screening even with twisted pairs.

Incidentally, balanced twisted pairs also radiate out much less, so crosstalk between circuits is very much reduced.

S
 
Data wiring twisted pair works on balanced transmission, just as it does for analogue audio. It works because the transmitter and receiver are both balanced and differential, so only respond to the difference in voltage between the two wires. External interference induces equally in the two wires, so cancels in the receiver. Balanced audio will work fine over unscreened twisted pairs for line levels, and not over long distances whereas low level microphone signals still need screening even with twisted pairs.

Incidentally, balanced twisted pairs also radiate out much less, so crosstalk between circuits is very much reduced.

S
Fair enough. I'm more technician than engineer so I'll take your word for it.

:)

My old Sansui won't be balanced on the inputs, so no twisted pairs here.....;)
 
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