Humming sound

[premkumar9]

Hi,
Can I take audio signal from the headphone socket of TV and 230VAC cable through the same conduit to the amplifier? Will it cause humming in audio due to 50Hz pick up from the power line? If so, what precautions to be taken?

 

[audioguru]

It is illegal to use one conduit for the power line and for anything else.
The amount of crosstalk depends on the output impedance of the headphones output.

 

[microtexan]

Humming

He's in India, I'm not sure anything like that is illegal If you can use a shielded cable , you might get away with it.

 

[premkumar9]

It is illegal to use one conduit for the power line and for anything else.
The amount of crosstalk depends on the output impedance of the headphones output.

You mean reducing the source impedance by using a buffer will reduce cross talk?

 

[premkumar9]

It is illegal to use one conduit for the power line and for anything else.
The amount of crosstalk depends on the output impedance of the headphones output.

What about stepping down the AC to 12V and taking through the same conduit? Will it reduce cross talk? Is it legal ?

 

[audioguru]

A buffer has a low output impedance. It is difficult to cause crosstalk interference to a low impedance.
12VAC produces much less crosstalk than 230VAC.

You should be asking these questions about the electricity laws in your country on a website in your country.

 

[premkumar9]

A buffer has a low output impedance. It is difficult to cause crosstalk interference to a low impedance.
12VAC produces much less crosstalk than 230VAC.

You should be asking these questions about the electricity laws in your country on a website in your country.

That is true. But in your country any power line through the signal conduit is restricted irrespective of level and whether it is DC or AC? Just for my information.

 

[audioguru]

In Canada and in the USA power lines have their own conduit and signals have their own conduit.

 

[Hero999]

A buffer has a low output impedance. It is difficult to cause crosstalk interference to a low impedance.
12VAC produces much less crosstalk than 230VAC.

You should be asking these questions about the electricity laws in your country on a website in your country.

Actually I doubty reduceing the voltage would solve the problem.

If the mains voltage were reduced to 12VAC then to deliver the same amount of power the current would need to be increased by a factor of 20. It depends on whether your system is more susceptable to electric fields or magnetic fields; if it's the former a higher voltage is worse and if it's the latter a higher current is worse.

 

[Andy1845c]

He's in India, I'm not sure anything like that is illegal

Legal or not, I wouldn't advise running a low voltage/signal line in the same conduit as a 230v ac main for safty reasons. Do you know anything about the wire in the conduit? Is it metal or plastic conduit? Whats the insulation on your signal wire rated at voltage wise?

Even if India is behind the USA in electric code, theres still a danger in doing this and a reason its illeagal.

 

[premkumar9]

Legal or not, I wouldn't advise running a low voltage/signal line in the same conduit as a 230v ac main for safty reasons. Do you know anything about the wire in the conduit? Is it metal or plastic conduit? Whats the insulation on your signal wire rated at voltage wise?

Even if India is behind the USA in electric code, theres still a danger in doing this and a reason its illeagal.

That is one reason for stepping down to 12V and sending. Do you think that this is also dangerous if it is through the same conduit?

 

[Andy1845c]

Well, I guess i'd rather come in contact with 12v then 240v. Is that practical though? What is the 240v ac for? If you want the same power you will need huge transformers at both ends and would have to pull a heavy wire though the conduit to make up the the increased current. It just dosn't sound practical. I'd rather run a seperate conduit for the signal wire then do all that.

 

[audioguru]

12V is not dangerous. But for the same power as a higher voltage then the current is much higher so the wire size must be much bigger.

 

[premkumar9]

Well, I guess i'd rather come in contact with 12v then 240v. Is that practical though? What is the 240v ac for? If you want the same power you will need huge transformers at both ends and would have to pull a heavy wire though the conduit to make up the the increased current. It just dosn't sound practical. I'd rather run a seperate conduit for the signal wire then do all that.

12 V line for these amplifiers only were audio level is low and hence power requirement is also low. Not for the entire supply in the hospital.

 

[premkumar9]

12V is not dangerous. But for the same power as a higher voltage then the current is much higher so the wire size must be much bigger.

Prepared to spend more on wires the for safety.

 

[mvs sarma]

12 V line for these amplifiers only were audio level is low and hence power requirement is also low. Not for the entire supply in the hospital.

Hope you realise that the hospital customers are at the risk of your experimentation. it would cause some problem if the end audio is given across the patients ears by a head phone? I feel we have to be more careful.

 

[premkumar9]

Hope you realise that the hospital customers are at the risk of your experimentation. it would cause some problem if the end audio is given across the patients ears by a head phone? I feel we have to be more careful.

I think, your comment is based on misunderstanding. The 12V line is a separate line for giving power to the amplifier at different locations. It is isolated using a transformer. No direct contact with anybody.

 

[mvs sarma]

I think, your comment is based on misunderstanding. The 12V line is a separate line for giving power to the amplifier at different locations. It is isolated using a transformer. No direct contact with anybody.

I can understand your point. I have been counseling a friend to design and implement remote amplifier with nominal pre-amplified signals coming from a remote location with battery fed from a central place. The moment a power line is switched on/off or a fan is switched on, (audio wires are in the same conduit of power), we had a hell of trouble. The thump and hum heard would be just crap.
After only separating them to another pre-earthed metal conduit , we were able to manage honorable audio.
In medical cases, the patience would be having low tolerence to disturbances, this is why i suggested that there is risk.

 

[premkumar9]

I can understand your point. I have been counseling a friend to design and implement remote amplifier with nominal pre-amplified signals coming from a remote location with battery fed from a central place. The moment a power line is switched on/off or a fan is switched on, (audio wires are in the same conduit of power), we had a hell of trouble. The thump and hum heard would be just crap.
After only separating them to another pre-earthed metal conduit , we were able to manage honorable audio.
In medical cases, the patience would be having low tolerence to disturbances, this is why i suggested that there is risk.

Thank you very much for your valuable advice based on real practical experience. I will definitely keep this point in mind.

 

[premkumar9]

How about converting to DC first and sending the DC through the conduit instead of AC? Will it improve cross talk problem?