Headphone jack mod

[lnx64]

I'm going to be installing a headphone jack on my Samsung, as im tired of waking up my room mate at night when watching TV..

So here's my plan, and someone correct me if I'm wrong.. The 20k20 chassis my TV has does indeed have an isolation transformer for the speaker, and the speaker is 8 ohms.

So here's what I'm gonna buy: http://www.radioshack.com/product/in...3038%3B+jacks#

A closed circuit headphone jack.

And if I got everything right, here's how I'll wire it..

EDIT: I can only find Stereo closed circuit jacks at RadioShack, so that's why it's wired this way.

[zeno]

If you want to be 100% sure I have seen sets with an output
transformer that one end of the speaker goes to hot ground anyways.
Did a lot of mods for sets going to the big house. Easiest way is
with a 1/4 jack & adapter. Usually the small ones arent long enuf to
go through the cabinet. Also the 1/4 is easier to work with
& wont fail with the cord pulling on the cheapo jack.


73 Zeno

[Celt]

Use a 100 ohm resistor to lower the output on the headphone jack.

[lnx64]

100 ohms ok. Is it ok to put before the speaker like I did but after the return pin? I'm not sure if I did that right.

[lnx64]

I see so many variations of this circuit, but all have the resistor before the jack, not after the return signal like mine..


This one looks like it'd make one side of the headphones not as loud as the other.. :/


and then this one:


Looks like it could work, and takes into account for them usually being stereo headphone jacks..

As for the 1/8th jacks not being long enough, i was going to dremel out an exact hole side into the side of the TV's cabinet, then use a slightly larger drill bit to "sink" it into the case a little.

[Jon A.]

If you're going to use a 1/4" connector, might I suggest using PO316 (B-gauge) connectors? They're professional-grade and hold up better under frequent insertion and removal.

[lnx64]

Question, why do the headphones need a resistor? If the original speaker is 8 ohms and the headphones are 32 ohms, wouldn't it already be a load?

[Chip Chester]

You are 9,482 times closer to the speaker in the headphones than you are to the speaker in the TV. Your useable audio adjustment range will be confined to the first 2.3 degrees of rotation of your volume control knob. Anything more than that will likely be PDL. Pretty darn loud.

Chip

[lnx64]

If the resistor is before the audio jack though when the headphones are unplugged wouldn't that cause the speaker to not be as loud too?

[Jon A.]

Just don't put the resistor between where the speaker lead from the chassis is connected to the headphone jack and the "normalizing" connection that goes to the built-in speaker from there. Assuming you're using a monaural jack, the resistor has to go between two of the pins on the jack, not before it. Finally, when using headphones, make sure each speaker impedance is no less than 16 ohms. Connecting speakers parallel cuts the impedance in half. Come to think of it, I don't think stereo headphones can be used in a monaural jack. Just bridge the tip and ring connectors at the jack with the resistor lead, easy enough.

[lnx64]

I'm confused I really need a schematic. Are any of the schematics I posted valid?

[Jon A.]

The first schematic looks pretty close; the stereo input/output pins will have to be bridged for the mono system, and the resistor placed between where the chassis speaker lead connects to the jack and the pins for headphone output.

[lnx64]

Ok so tue third one should work then. The 2nd one looks like it'd cause balance issues on the headphones.

[Jon A.]

Just a heads-up, I'm not sure if the diagram in the original post would be considered a schematic, but that's what I was looking at when I posted last. The others I saw were a bit confusing to me. Also, I'm pretty sure that you need only one resistor. I'm pretty sure that ohm's law also applies to resistors; connecting those parallel will halve the resistance.

[lnx64]

Yea I'm gonna just use one 100ohm resistor and tie it to both l and r on the headphones jack and the speaker in the tv only to one of the returns.