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RCA cable question

post #1 of 31
10/20/12 at 6:44pm
Thread Starter 
Dumb question but for the RCA cable (say for subwoofer pre) The metal shield ring does it need to connect to the outer part of the cable? What happens if it's not?
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post #2 of 31
10/21/12 at 4:16am
Quote:
Originally Posted by SubaruB4 View Post

Dumb question but for the RCA cable (say for subwoofer pre) The metal shield ring does it need to connect to the outer part of the cable?

Yes, if by outer part you mean the shield of the cable. If you mean the plastic jacket, then that connection is only mechanical, and not electrical.
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What happens if it's not?

Generally, you get hum - lots of it.
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post #3 of 31
10/21/12 at 9:01am
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What happens if it's not?

Then you don't have a complete circuit and no audio signal will flow.
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post #4 of 31
10/21/12 at 9:43am
Quote:
Originally Posted by SAM64 View Post

Then you don't have a complete circuit and no audio signal will flow.
Check into that. It's not a circuit (like speaker wiring). It's signal (pin) and ground (sheath). Arny has it correct. Hum with no ground.
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post #5 of 31
10/21/12 at 9:57am
Quote:
Originally Posted by Ratman View Post

Check into that. It's not a circuit (like speaker wiring). It's signal (pin) and ground (sheath). Arny has it correct. Hum with no ground.

Right. The important point to realize is that if you are working with equipment that is connected to the power line, and particularly if the equipment has a 3 prong plug, the circuit with the broken shield connection is completed through the 3 prong plug ground.

Unintentional grounding is usually flakey and that's where the hum comes from.
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post #6 of 31
10/21/12 at 10:21am
Thread Starter 
I ended up blowing one of the amps last night in a computer speaker when testing I was trying to do a stand alone sub for a temporary setup, well the magic smoke came out hah I guess I will just do the two weeks without a sub.
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post #7 of 31
10/21/12 at 11:09am
Two prong or three prong AC, should not make a difference (assuming all AC wiring/outlets are up to code)

Quote:
Originally Posted by SubaruB4 View Post

I ended up blowing one of the amps last night in a computer speaker when testing I was trying to do a stand alone sub for a temporary setup, well the magic smoke came out hah I guess I will just do the two weeks without a sub.
.

That's different can o' worms!

Ask first.... then test. wink.gif
Computer audio cards, computer speakers and "standalone" sub setups can be tricky. (In other words.... a hodge-podge setup)

What exactly is the nature of your question? Bad cables, connections or an explanation why you blew up an amp. biggrin.gif
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post #8 of 31
10/21/12 at 1:04pm
Slight correction. The 3 rd pin on the AC cord is NOT intended to be return for the audio path in any audio circuit. The ground /shield IS most certainly part of the audio circuit. Many audio devices have a pseudo floating audio ground path. They may have a .01 mfd disc cap in series with something on the order of a 51 ohm resistor between the audio path ground and the DC power supply ground and chassis. This is usually sufficient to provide grounding from AC hum in the audio path. Attempting establish an audio path using ONLY the center pin of a single ended audio interconnect and expecting the AC chassis ground to provide an effective audio ground will result in just plain audio hash and distortion and hum.
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post #9 of 31
10/21/12 at 2:36pm
Thread Starter 
Quote:
Originally Posted by Ratman View Post

Two prong or three prong AC, should not make a difference (assuming all AC wiring/outlets are up to code)
.
That's different can o' worms!
Ask first.... then test. wink.gif
Computer audio cards, computer speakers and "standalone" sub setups can be tricky. (In other words.... a hodge-podge setup)
What exactly is the nature of your question? Bad cables, connections or an explanation why you blew up an amp. biggrin.gif

Heh well I had to stop midway yesterday to go to a party and when I got back late at night I started working again lol bag decision! Well anyways long story short I have this same sub here in post # 5th down

http://www.neoseeker.com/forums/704/t828474-use-z680-sub-on-an-standalone-amps-pre-out/#pagetop

"If any people are (like I was) looking for a way to use the amplifier with out the control pod heres my little guide..

1. Take the amplifer off the subwoofer. (I needed to cut some wires here to get it off enough)

2. Take off the back plate (lots of screws to undo here including some with bolts on the other side)

3. Take off the panel on the rear side which has the plug to the control panel. (once you've removed the bolts it just pulls off)

4. Now using the pin labels that you will find on the panel that you pulled off identify the VREGDD, MUTE AMP and STANDBY AMP pins (they are all in a line), use some single core wire to connect mute and standby to the vregdd (or put switches on) This will allow the amp to be turned on with out the control pod being attached.

5. connect the inputs (eg RF AMP etc) to some sort of connectors ie 3mm or coax connections.

And Thats it, make sure if you cut any wires to ease the amp off you fix them back up and cover with electrical tape

Now the amp can be turned on/off by the switch on the back or if you put switches on the STANDBY AMP Wire. One thing to note though is that the Amp now has no Pre-Amp which means no onbard volume control or crossovers so make sure you turn the volume right down on the source before you plug it in!!"

In my case I connected the RCA cable to the pin labeled SUB on the board but I left the ground disconnected at one end, Not sure why the audio chip blew (tda7293)
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post #10 of 31
10/22/12 at 6:35am
Quote:
Originally Posted by SubaruB4 View Post

Not sure why the audio chip blew (tda7293)
Rule #1: don't experiment late at night
Rule #2: don't work on electronics with a load on.

Verify the wiring. Wire as instructed. Also, look for stray/uninsulated unused wires. (When fully awake and sober smile.gif )
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post #11 of 31
10/22/12 at 8:56am
Quote:
Originally Posted by Ratman View Post

Check into that. It's not a circuit (like speaker wiring). It's signal (pin) and ground (sheath). Arny has it correct. Hum with no ground.

No, sorry...you need to check your facts for a change.
A complete circuit requires both conductors.....this is basic electronics...please don't embarrass yourself by arguing this.
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Right.

no, he's not.
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post #12 of 31
10/22/12 at 11:33am
LOL... okay.
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post #13 of 31
10/22/12 at 12:04pm
Thread Starter 
Quote:
Originally Posted by Ratman View Post

Rule #1: don't experiment late at night
Rule #2: don't work on electronics with a load on.
Verify the wiring. Wire as instructed. Also, look for stray/uninsulated unused wires. (When fully awake and sober smile.gif )

Haha yeah sounds like a plan
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post #14 of 31
10/22/12 at 12:11pm
Rule #3: Don't take advice from someone with only a rudimentary knowledge of electronics.
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post #15 of 31
10/22/12 at 1:28pm
Quote:
Originally Posted by SAM64 View Post

Rule #3: Don't take advice from someone with only a rudimentary knowledge of electronics.
Rather than throw out hostilities in this and every thread you "visit", just provide the answer (detailed, if possible) to the OP"s question/problem. rolleyes.gif

EDIT:
Just for your info.
There were two other contributors that were in line with my thoughts. Pick on them also. tongue.gif
Edited by Ratman - 10/22/12 at 1:33pm
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post #16 of 31
10/22/12 at 1:54pm
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There were two other contributors that were in line with my thoughts.

So? They're not as arrogant and condecending as you are.

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Pick on them also.

Post accurate information or don't post....and don't tell others what to do.
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post #17 of 31
10/22/12 at 2:11pm
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Originally Posted by SAM64 View Post

So? They're not as arrogant and condecending as you are.
Post accurate information or don't post....and don't tell others what to do.

Without commenting on this particular debate, if that's the new AVS standard, traffic is going to go way, way down. eek.gif
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post #18 of 31
10/22/12 at 2:38pm
Quote:
Originally Posted by SAM64 View Post

So? They're not as arrogant and condecending as you are.
Post accurate information or don't post....and don't tell others what to do.

Turn it around and I am in complete agreement! smile.gif
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post #19 of 31
10/25/12 at 10:30am
Thread Starter 
Well I think I saw my issue.. when i hooked up the subwoofer cable I did not know that the connections I made on the amp left a short circuit, I pretty much saw it when I cut the heatsrink tubing away, one of the aftermath pictures DSC00541.jpg

fixed it but will need to replace the tda7293 that blew for the sub.. funny it still blew without the shield ground on the amp but the jack to the wire area is where it was shorted a good distance away from the amp..

DSC00543.jpg
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post #20 of 31
10/25/12 at 11:23am
Quote:
Originally Posted by bfreedma View Post

Without commenting on this particular debate, if that's the new AVS standard, traffic is going to go way, way down. eek.gif

it's not a standard, don't worry about it.
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post #21 of 31
10/25/12 at 12:29pm
Quote:
Originally Posted by SubaruB4 View Post

Well I think I saw my issue.. when i hooked up the subwoofer cable I did not know that the connections I made on the amp left a short circuit, I pretty much saw it when I cut the heatsrink tubing away,

fixed it but will need to replace the tda7293 that blew for the sub.. funny it still blew without the shield ground on the amp but the jack to the wire area is where it was shorted a good distance away from the amp

Looks like the advice provided in post #10 paid off (no matter what others think). biggrin.gif
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post #22 of 31
10/25/12 at 4:33pm
Thread Starter 
haha now just have to wait for the replacement parts now biggrin.gif
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post #23 of 31
10/26/12 at 4:18am
Quote:
Originally Posted by Ratman View Post

Looks like the advice provided in post #10 paid off (no matter what others think). biggrin.gif

LOL....actually it's the opposite. ....regardless of what you think.
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post #24 of 31
10/26/12 at 7:39am
Thread Starter 
I don't know what you two have going on but maybe take it to a private message?

To be fair I was asking on a electronics site since these Audio IC are something I haven't messed with yet anyways I talked about how I have the cable and they are telling me that the shield should be connected to earth ground at one side only, however the sending device also needs a ground!

having said that, that's the whole reason why RCA cables have a foil shield and the shield wire is around it.
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post #25 of 31
10/26/12 at 9:34am
http://www.bluejeanscable.com/articles/shielding.htm
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post #26 of 31
10/26/12 at 9:49am
Quote:
Originally Posted by SubaruB4 View Post

I don't know what you two have going on but maybe take it to a private message?
To be fair I was asking on a electronics site since these Audio IC are something I haven't messed with yet anyways I talked about how I have the cable and they are telling me that the shield should be connected to earth ground at one side only, however the sending device also needs a ground!
having said that, there definitely won't be any rolloff for high audio frequencies, that's for sure..

In an unbalanced interconnect, such as the ones you have, the shield, which should be at ground potential has to be connected at both ends in order for current, and thus a signal, to be available at the other end.

Not all 'RCA' cables have a foil shield. Not all coax cables have a foil shield either. Drain wires are used with foil shields due to their poor conductivity.
Not sure what you mean by this:
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there definitely won't be any rolloff for high audio frequencies, that's for sure.
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post #27 of 31
10/26/12 at 10:20am
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Originally Posted by SAM64 View Post

Not sure what you mean by this:
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there definitely won't be any rolloff for high audio frequencies, that's for sure.

The bolded quote (to which you referenced) is from a different thread. I'm not sure what you mean by this (as it pertains to this thread).
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post #28 of 31
10/26/12 at 10:25am
Quote:
The bolded quote (to which you referenced) is from a different thread

gee, I wonder why it was actually posted in this thread ...and then edited out.




[EDIT] Please do not make personal remarks/attacks.
Thanks
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post #29 of 31
10/26/12 at 11:57am
I must have missed that. I saw that originally in this thread by a different poster (post #283)

http://www.avsforum.com/t/1379661/does-expensive-speaker-and-interconnect-cables-really-make-a-difference/270

.... but a post that is not part of this thread.

As for "upping post count", that's not my intention. Been here ten years.
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post #30 of 31
10/26/12 at 5:09pm
The concept of connecting the shield on an audio interconnect on one end only applies ONLY to balanced line level signals and 95% of the time a fully connected shield on BOTH ends of the interconnect from source to input is never a pro0blem.
OCCASIONALLY there is a ground conflict that MAY be resolved by lifting a shield. There is no blanket rule on which end should be lifted . I have had positive results when lifting the shield (pin 1) was achieved at either end. It is a case by case operation.

Whenever I encounter a ground/hum issue I use an isolation transformer and have had stellar results every time. That is why I have built and sold so many. Hi-Z and balanced.
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