Connecting speaker output to line input

[5016]

I have a Panasonic plasma TV. It has multiple audio and video inputs
but no line level audio output. What it does have is 2 speaker level
outputs for 2 optional 8W speakers. What I'd like to do is connect
these outputs directly to a spare set of NHT powered monitors that I
have, in order to minimize the number of connections so that this
device can be operated easily by my wife and daughter.

Clearly, connecting speaker outputs to line level inputs is not a good
thing. My knowledge of electronics is shaky at best, but I'd have
thought that I could connect some kind of inductor to step down the
signal to some appropriate level. Is this possible, and if so, how?

Thanks very much for any ideas you have!

[Eeyore]

5016 wrote:

> Clearly, connecting speaker outputs to line level inputs is not a good
> thing. My knowledge of electronics is shaky at best, but I'd have
> thought that I could connect some kind of inductor to step down the
> signal to some appropriate level. Is this possible, and if so, how?

You need an attenuator 'pad' made from a couple of resistors. 33k and 1k would
probably work fine. Connect the 2 resistors in series with the speaker output
connected to the 'far end' of the 33k. Connect the junction of the 2 resistors
to the line input and the remaining connection to the 1k to ground (use the
screen/shield of the line input).

Graham

[ScottW]

"5016" > wrote in message
ups.com...
>I have a Panasonic plasma TV. It has multiple audio and video inputs
> but no line level audio output.

I find this a bit hard to believe. A plasma TV with no
audio out? What model?
Even their cheapest current model has audio out.

ScottW

[5016]

On May 13, 5:29 pm, "ScottW" > wrote:
> "5016" > wrote in message
>
> ups.com...
>
> >I have a Panasonic plasma TV. It has multiple audio and video inputs
> > but no line level audio output.
>
> I find this a bit hard to believe. A plasma TV with no
> audio out? What model?
> Even their cheapest current model has audio out.
>
> ScottW

Panasonic TH-37PWD6. It's not a current model.

[5016]

On May 13, 4:51 pm, Eeyore >
wrote:
> 5016 wrote:
> > Clearly, connecting speaker outputs to line level inputs is not a good
> > thing. My knowledge of electronics is shaky at best, but I'd have
> > thought that I could connect some kind of inductor to step down the
> > signal to some appropriate level. Is this possible, and if so, how?
>
> You need an attenuator 'pad' made from a couple of resistors. 33k and 1k would
> probably work fine. Connect the 2 resistors in series with the speaker output
> connected to the 'far end' of the 33k. Connect the junction of the 2 resistors
> to the line input and the remaining connection to the 1k to ground (use the
> screen/shield of the line input).
>
> Graham

Thanks very much!

If you don't mind, I'm going to reiterate so I'm sure I've understood,
using an RCA connector for the line input.

Connect the positive speaker output (red) to a 33K resistor. Connect
the other end of the 33K resistor to the "centre" of the RCA
connector, and also to a 1K resistor. Connect the outer part of the 1K
resistor to the "outside" of the RCA connector.

This leaves the negative speaker output (black) not connected to
anything. Is this OK?

Thanks again -

[ScottW]

"5016" > wrote in message
ps.com...
> On May 13, 5:29 pm, "ScottW" > wrote:
>> "5016" > wrote in message
>>
>> ups.com...
>>
>> >I have a Panasonic plasma TV. It has multiple audio and video inputs
>> > but no line level audio output.
>>
>> I find this a bit hard to believe. A plasma TV with no
>> audio out? What model?
>> Even their cheapest current model has audio out.
>>
>> ScottW
>
> Panasonic TH-37PWD6. It's not a current model.

Its not a TV. Its a plasma display primarily for computers
but it does have RGB input.

Whatever you're sourcing video with (DVD, PC,
cable box..) will have line level audio out.
Take it from there.

ScottW

[Eeyore]

5016 wrote:

> On May 13, 4:51 pm, Eeyore >
> wrote:
> > 5016 wrote:
> > > Clearly, connecting speaker outputs to line level inputs is not a good
> > > thing. My knowledge of electronics is shaky at best, but I'd have
> > > thought that I could connect some kind of inductor to step down the
> > > signal to some appropriate level. Is this possible, and if so, how?
> >
> > You need an attenuator 'pad' made from a couple of resistors. 33k and 1k would
> > probably work fine. Connect the 2 resistors in series with the speaker output
> > connected to the 'far end' of the 33k. Connect the junction of the 2 resistors
> > to the line input and the remaining connection to the 1k to ground (use the
> > screen/shield of the line input).
>
>
> Thanks very much!
>
> If you don't mind, I'm going to reiterate so I'm sure I've understood,
> using an RCA connector for the line input.
>
> Connect the positive speaker output (red) to a 33K resistor. Connect
> the other end of the 33K resistor to the "centre" of the RCA
> connector, and also to a 1K resistor. Connect the outer part of the 1K
> resistor to the "outside" of the RCA connector.

Correct.


> This leaves the negative speaker output (black) not connected to
> anything. Is this OK?

It is.

Graham

[Sander deWaal]

Eeyore > said:


>> If you don't mind, I'm going to reiterate so I'm sure I've understood,
>> using an RCA connector for the line input.


>> Connect the positive speaker output (red) to a 33K resistor. Connect
>> the other end of the 33K resistor to the "centre" of the RCA
>> connector, and also to a 1K resistor. Connect the outer part of the 1K
>> resistor to the "outside" of the RCA connector.


>Correct.


>> This leaves the negative speaker output (black) not connected to
>> anything. Is this OK?


>It is.


Uhm???
No ground connected?

The negative speaker output should be connected to the ground of the
line input, that is the outer ring of the cinch connector.

--

- Maggies are an addiction for life. -

[Eeyore]

Sander deWaal wrote:

> Eeyore > said:
>
> >> If you don't mind, I'm going to reiterate so I'm sure I've understood,
> >> using an RCA connector for the line input.
>
> >> Connect the positive speaker output (red) to a 33K resistor. Connect
> >> the other end of the 33K resistor to the "centre" of the RCA
> >> connector, and also to a 1K resistor. Connect the outer part of the 1K
> >> resistor to the "outside" of the RCA connector.
>
> >Correct.
>
> >> This leaves the negative speaker output (black) not connected to
> >> anything. Is this OK?
>
> >It is.
>
> Uhm???
> No ground connected?

No need. The speaker 'negative' (normally !) is grounded within the equipment.


> The negative speaker output should be connected to the ground of the
> line input, that is the outer ring of the cinch connector.

Absolutely NOT !

You could end up with uncontrolled ground currents. Or worse, speaker level
currents being drawn through the line input circuitry !

Graham

[Sander deWaal]

Eeyore > said:


>Sander deWaal wrote:

>> Eeyore > said:


>> >> If you don't mind, I'm going to reiterate so I'm sure I've understood,
>> >> using an RCA connector for the line input.


>> >> Connect the positive speaker output (red) to a 33K resistor. Connect
>> >> the other end of the 33K resistor to the "centre" of the RCA
>> >> connector, and also to a 1K resistor. Connect the outer part of the 1K
>> >> resistor to the "outside" of the RCA connector.


>> >Correct.


>> >> This leaves the negative speaker output (black) not connected to
>> >> anything. Is this OK?


>> >It is.


>> Uhm???
>> No ground connected?


>No need. The speaker 'negative' (normally !) is grounded within the equipment.


Yep, and he is using an external amplifier.


>> The negative speaker output should be connected to the ground of the
>> line input, that is the outer ring of the cinch connector.


>Absolutely NOT !

>You could end up with uncontrolled ground currents. Or worse, speaker level
>currents being drawn through the line input circuitry !


Through a voltage divider, consisiting of 33k and 1k?
Again, the OP is using an *external* amplifier, unless I missed
someting.

--

- Maggies are an addiction for life. -

[Arny Krueger]

"5016" > wrote in message
ups.com
> I have a Panasonic plasma TV. It has multiple audio and
> video inputs but no line level audio output. What it does
> have is 2 speaker level outputs for 2 optional 8W
> speakers. What I'd like to do is connect these outputs
> directly to a spare set of NHT powered monitors that I
> have, in order to minimize the number of connections so
> that this device can be operated easily by my wife and
> daughter.
>
> Clearly, connecting speaker outputs to line level inputs
> is not a good thing.

When you're talking 8 watts from a TV, it isn't nearly as bad as it may
seem.

> My knowledge of electronics is shaky
> at best, but I'd have thought that I could connect some
> kind of inductor to step down the signal to some
> appropriate level.

Like you said, very shakey knowlege, and wrong.

> Is this possible, and if so, how?

Frankly, a direct connection of an 8 watt line to a line level input is not
all that bad of a marriage. Just be careful to not short out the speaker
line.

If you want a pre-packaged tool, try one of these:

http://www.epanorama.net/circuits/speaker_to_line.html

http://www.hometech.com/audio/spline.html

http://www.crutchfield.com/S-JeByplNyo3V/cgi-bin/prodview.asp?i=142SLC4

[Kalman Rubinson]

While it is relatively easy to make the kind of voltage divider that
others have described, you can just go to any auto-audio shop or
search the internet for speaker-to-line adapters. All packaged
with the appropriate connectors.

Kal