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Audio Distribution

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premkumar9

Member
Line output level is not varied by the volume control and its impedance is typically 10K; much higher than earphone output.
Earphone output is typically 200 to 600 Ohms output impedance and its amplitude varies by the volume control
Normally the headphone output from TV is AC coupled OR DC coupled?
Is that ground connected to TV circuit ground OR isolated?
 

transistor495

Member
Forum Supporter
I assume this is same for your hospital application :)
I will give you some another idea.
Take L and R of Line-out of your TV and connect it into voltage amplifier/line distributer system. Feed it to each speaker points using shielded cables along with 230V supply line. It should be perfect and don't make them adjacent.
Contact some industry and make required number of 3" amplified speakerboxes using TA7368P(1W) IC which is fairly enough with ON/OFF and volume on preset.
I think you can smell some benefits over that :rolleyes:
 

Dean Huster

Well-Known Member
In the olden days of audio, we used a 70v line amp, matching transformers and pads at each remote speaker. In fact, most of the PA systems back then had outputs for 4, 8 or 16 ohms and 25V or 70V line. Easy. Simple. And you don't have to worry about cable length.

Dean
 

premkumar9

Member
I assume this is same for your hospital application :)
I will give you some another idea.
Take L and R of Line-out of your TV and connect it into voltage amplifier/line distributer system. Feed it to each speaker points using shielded cables along with 230V supply line. It should be perfect and don't make them adjacent.
Contact some industry and make required number of 3" amplified speakerboxes using TA7368P(1W) IC which is fairly enough with ON/OFF and volume on preset.
I think you can smell some benefits over that :rolleyes:
I checked the TV sets already installed at the hospital. I think there is only one Audio out, that is the head phone out. All others are audio inputs only. So I have to take that only. The problem is it will cut the TV speakers and level will vary with TV volume control. Right?
 

transistor495

Member
Forum Supporter
I'm not much sure about using the headphone jack. It will cut TV speakers when audio pin is inserted also it is subjected to TV volume control level.

Line-Outs are pre-amplified outputs for connecting to external power amplifiers.
Headphone out actually like a speaker output.

It was bad idea that you have installed the TV set without a Line-Out prior to the 'audio distribution' requirement. right?

Maybe some technician can help you to figure out a Line-Out from your TV set. Again rounded way!
 

transistor495

Member
Forum Supporter
Is it possible that taking input from the headphone jack may make the audio noisy?
No. I'll explain.
The output for headphone is something 100mW of power amplified output, which is very low.
In this case you have to use lengthy cables for splitting it and to feed it to something a maximum of 30 speakers distributed over the hall. Right?
That 100mW of power will be equally distributed to 30 speakers and as a result you will get.......................nothing :D for amplification.

I think it will badly affect your headjack circuit in TV for overloads!!
 

premkumar9

Member
No. I'll explain.
The output for headphone is something 100mW of power amplified output, which is very low.
In this case you have to use lengthy cables for splitting it and to feed it to something a maximum of 30 speakers distributed over the hall. Right?
That 100mW of power will be equally distributed to 30 speakers and as a result you will get.......................nothing :D for amplification.

I think it will badly affect your headjack circuit in TV for overloads!!
Not like that. There is going to be a distribution amplifier near the head phone and one amplifier with each speaker. Both these I will make myself. loading of the headphone point will be taken care of. My doubt is whether taking signal from line O/P and head phone jack will make any difference as far as audio quality is concerned.
 

transistor495

Member
Forum Supporter
Audio quality will be good anyway for headjack. But don't forget to use that distribution amplifier, that's what I meant!

1yr before I have made an ipod amplifier using TA7368P(1W Toshiba) IC. I've built -in it inside a 3" speakerbox and it was very good for private listening. The IC is very common and cheap one. It uses an ultra simple circuit. I think you can implement your speakerbox in this way.
 

premkumar9

Member
The head phone socket is directly connected to the speaker points through a socket which connects either one at a time. Am I right?
 

premkumar9

Member
Line output level is not varied by the volume control and its impedance is typically 10K; much higher than earphone output.
Earphone output is typically 200 to 600 Ohms output impedance and its amplitude varies by the volume control
In the TV that is already installaed, there is no line output. Only headphone output available. Here the problem is if I take the audio from head phone o/p,
1. The volume of the other speakers also will change if Tv volume is adjusted.
2. TV speakers will be disconnected when I insert the jack to the headphone socket.
Any suggestion to avoid the above?

Just now I have checked one MP3 CD player which has both headphone and line outputs. But for both that outputs level is varying with volume control.:(
 

transistor495

Member
Forum Supporter
Any suggestion to avoid the above?

Just now I have checked one MP3 CD player which has both headphone and line outputs. But for both that outputs level is varying with volume control.:(
Mr Premkumar9,
Think freely..your headphone out is subjected to tv volume control, so if you want to avoid that the only option is to open the tv cabinet and take a Line-Out by the help of a technician. Correct?

MP3 players normally will not have built-in speakers. So their audio out should be controlled by volume control. Think and compare it with a tv with built-in speaker which is normally used.

You can either take a Line-Out from your tv by opening it.

Otherwise take the headphone out and amplify it using a distribution amp and input to each speakers. TV speakers will off. ok?
 

premkumar9

Member
MP3 players normally will not have built-in speakers. So their audio out should be controlled by volume control. Think and compare it with a tv with built-in speaker which is normally used.
Kindly understand my question. I said both head phone and line O/P are varing with volume control and level also seems to be same. So couldn't understand the purpose.
 

transistor495

Member
Forum Supporter
Kindly understand my question. I said both head phone and line O/P are varing with volume control and level also seems to be same. So couldn't understand the purpose.
Suppose you are listening to headphone now :)
You can either use vol control button on player(you are sitting near to player) or remote(you won't use).

Now suppose you have connected Line-Out to an amplifier.
You can use your remote to control volume easily or button on player(you won't use) :D


Headphone out is power amplified and intended for headphone impedance.

For connecting to external amplifier, Line-out is provided(voltage amplified, should be power amplified)

In a TV set suppose you have connected Line-out to an external power amplifier. You can use TV remote vol control(or button on tv) to adjust TV speaker volume for effects(TV speaker will act as a center speaker). In this case you have to use external amp volume control manually.
 
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