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A few Earphone/Headphone jack questions...???

 
 
BIG DAVE
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      12-28-2010
Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
a PC, it SEEMS that they are one and the same however on any stereo or
radio I have if I hook up a small speaker through the earphone/
headphone jack the sound coming from the speaker is very low.

I know that there are things such as matching impedence etc... But
even after trying several speakers, the output seems low. Problem
is... if it's NOT the same it seems that most music players or even
radios these days don't have external speaker jacks and just have the
headphone jack.

Thanks

DAVE
 
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richard
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      12-29-2010
On Tue, 28 Dec 2010 13:42:20 -0800 (PST), BIG DAVE wrote:

> Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
> a PC, it SEEMS that they are one and the same however on any stereo or
> radio I have if I hook up a small speaker through the earphone/
> headphone jack the sound coming from the speaker is very low.
>
> I know that there are things such as matching impedence etc... But
> even after trying several speakers, the output seems low. Problem
> is... if it's NOT the same it seems that most music players or even
> radios these days don't have external speaker jacks and just have the
> headphone jack.
>
> Thanks
>
> DAVE


Yes, the jacks are different. Headphones generally have a higher impedance
than standard speakers, which are typically set at 8 ohms.
If the output appears to be low, then you might have to add a small preamp
inline.
 
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PeeCee
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      12-29-2010
On 29/12/2010 10:42 a.m., BIG DAVE wrote:
> Is a Earphone/Headphone jack the same as an EXTERNAL SPEAKER jack? On
> a PC, it SEEMS that they are one and the same however on any stereo or
> radio I have if I hook up a small speaker through the earphone/
> headphone jack the sound coming from the speaker is very low.
>
> I know that there are things such as matching impedence etc... But
> even after trying several speakers, the output seems low. Problem
> is... if it's NOT the same it seems that most music players or even
> radios these days don't have external speaker jacks and just have the
> headphone jack.
>
> Thanks
>
> DAVE



Dave


The output level from an External Speaker jack hand depends very much on
the design of the particular hardware and what it is intended to drive.
If the device is designed to drive bare unamplified speakers then the
output level will depend on the size of the power amplifiers built into
the device. eg 500Watt Surround sound Amplifier, TV, Radio etc...
The physical size of the speakers needed is irrelevant.
However parameters like power handling, frequency response, impedance
are relevant in that they should match the device they are plugged into.

Typical speaker parameters are in the lower impedance range eg. 4 to 8
ohms (exceptions of course, like the old Philips Hi Impedance range)

The output level from a 'headphone' jack on the otherhand is limited by
design to minimise potential hearing and hardware damage.
(headphone includes earphone in this context)
A lot of countries have health and safety limits on the maximum sound
level a headphone can deliver to the wearers ears.
To meet these legislative and physical constraints circuit elements are
introduced between Amplifier and the headphone socket so it doesn't blow
the headphones or the wearers ears up.
(roughly <100 milli watts 'maximum')
Note this is 'Even if the amplifier is capable of hundreds of watts
output to speakers'

Typicaly headphones today also tend to have higher impedances, eg up to
32 ohms impedance.

Therefore when you plug a low impedance speaker into a high impedance
(headphone) output the speaker is:
(a) not matched correctly for maximum power transfer 'and'
(b) the headphone circuitry simply can't deliver the 'amount' of power
to drive the speaker hard enough to hear it without close coupling to
your ear (as in headphones)
*this is why your speaker experiments sounded so quiet*



FYI PC sound cards were originally designed to drive plain 'unamplified'
speakers (think the original Soundblaster cards)
Plugging a set of headphones into those outputs required you to turn the
sound level 'wayyyyy' down if you valued you hearing and/or headphones.

Later on the sound card makers transfered these Amplifiers from the
Sound Card to the external speakers that were plugged into these new
design cards.
The point in the circuitry they put the output socket was roughly
equivalent to the power and impedance of a headphone socket.
Hence the 'Speaker/Headphone' designation.

So a pair of (amplified) PC speakers can be plugged into a PC sound card
'speaker/headphone' socket and sound just as loud as the old onboard
amps to a plain unamplified speakers.

The same amplified PC speakers plugged into the 'headphone' socket of a
DVD player, Radio, TV etc would also give similar volume as the driving
device is matched correctly to the (amplified) speakers.
The power to drive the speakers loud enough to hear across the room
comes from the speakers built in amplifiers not from the output of the
headphone socket.

Best
Paul.
 
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BIG DAVE
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      12-29-2010
Thanks for the replies. Paul, I especially found your reply both
thorough and informative.

DAVE

 
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