Headphone jack mod
 

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.

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:smoke:

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

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.

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.. :/
http://www.ve3syb.ca/radio/icf2010-phonejack.jpg

and then this one:
http://antiqueradios.com/forums/down...e.php?id=11928

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.

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.

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?

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

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?

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.

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

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.

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

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.

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.

I'm not sure what you're talking about there, sounds like extra resistance will be going to the built-in speaker, can't have that. By the way, ever get the ultrasonic hearing issue sorted out with the roomie? Oh, my bad, you must have, otherwise the telly would be waking her up even with the volume all the way down.

Never did but she quit complaining about that.

I really don't understand then. Someone needs to draw it out on paper what I'm to do.

I'm slightly autistic so I don't always understand what to do when spoken out and just need a schematic.

Unfortunately I can't do drawings on my computer, so I'll do my best to water down my tech-talk. By the way, I have a high-functioning sort of autism called Asperger's syndrome.

Do you have a multi-meter that can be set on ohms? Or better yet, a diagram that came with the jack? I assume that the "returns" you speak of are the left/right speaker + connectors that will be going to the built-in speaker, two terminals that will have to be connected together before going to the speaker, no resistor needed there. Without headphones plugged in, you'll have a direct chassis-to-speaker connection through the jack. The left/right + terminals on the chassis side of the jack will have to be bridged as well, and the resistor connected between those and the pins that are only active with headphones plugged in, which also have to be bridged.

Yep aspergers here too. I do in fact have a multimeter, oscilloscope too.

I think this makes sense I will try it tomorrow.

Good stuff. No need for any fancy footwork with the ground connections of course, it's just a single wire going to single terminals on the speaker and the jack. Direct connect all around.

Sometimes I have to re-read things a few times before I actually "get it". It can be frustrating.

So here's a problem I'm trying to work out. The headphone jack has its returns which are going right to the built in speaker, directly connected to the inputs on the jack when no headphones are plugged in. What I see is any resistor on the headphones, are directly going to affect the speaker no matter what.

This may be ok though, the speaker is far too loud easily as the knob is very sensitive.

That seems odd to me. Only one side of that resistor would be technically "connected" to anything without headphones plugged in. I don't see how that could possibly affect the built-in speaker's performance.

This is probably why I still need a schematic drawn up. I can wait to so it so you can help me with this.

One disadvantage in using a Mac, it doesn't even have a paint program. It's my only computer. The GIMP program isn't an option at this time, it would take forever to bring down over my connection. Kind of pointless to download it to make only one drawing anyway. The only practical solution is for me to draw one up by hand, then take it to the library and run it through a scanner (another thing I lack), unless someone else can chime in first.

Well I tried to cheat. The hitachi my little sister now had from my sig had a headphone jack, and I peaked at how it's wired. It wired like this.

Speaker directly to negative.
Headphone jacks return directly wired to speakers positive.
Headphone jacks tip wired directly to positive.
Headphone jack wired to negative with a resistor.

Does that sound right and feasible for use in my Samsung?

Lol wait. Why do I have a weird feeling this is basically what you were saying?

I never thought of tying the resistor to ground, sounds like it could work. That would be a mono jack if it's a factory setup. You would need to bridge the jack inputs together and the jack outputs together on your set though.

Edit: Close enough. :)

Yep. I know it'd need to be bridged on the inputs. I got that easily figured out.

Well, it's installed, and it worked! I did have to counter sink the jack, but check this sucker out, that looks stock!

http://img.photobucket.com/albums/v3...9.jpg~original

http://img.photobucket.com/albums/v3...9.jpg~original

Ah, very good. :)

Only annoying thing though is I can hear the 60hz hum in the headphones even with the volume turned down.

Uh oh, sounds like tying the resistor to ground may have caused a ground loop issue. You might need to move that resistor between the jack input and headphone output as I originally instructed.

Actually, I forgot to mention, the speaker normally does this on it's own too :/ For some reason the TV just has it in the audio signal.

If I feed the TV a PAL video signal, it becomes a 50Hz hum, so it's coming from the vertical retrace.

Hmm, bad filter cap somewhere I suspect. You could have a cap that's completely open, causing the vertical retrace to cross-couple into the audio circuit. One time, when I was a lot younger and didn't know nearly as much about what I was doing, I over-volted an under-dash 8-track player, which soon blew the side out of a cap. Good thing the top didn't blow out, I was looking into the player when the cap blew. Running it without the cap caused noise in the audio.

This is the buzz I hear btw.

http://www.mediafire.com/listen/uf2b...yc1/tvbuzz.mp3

This has happened on the TV since I got it through it's built in speaker. Does it on UHF and VHF. In the audio I'm turning the volume up and down. When cranked up all the way, the noise changes to a weird space ship sound..

I can't hear anything that I would consider out of the ordinary, even with my computer's main volume control and the Quicktime player volume all the way up. Of course I have only one tiny speaker, and it's built into the tower, which of course is on the floor. I leaned in closer to it though, still couldn't hear anything.

There's definitely a buzz.. Shows up on my oscilloscope and Audacity..

Unfortunately I can't think of anything else that might be wrong. I suppose the bad/open cap, if any, could be in the audio circuit as well. Sounds like you have a good complement of equipment there. Should set yourself up with an ESR meter if you haven't already.

Don't have one sadly.

Might try playing with the video signal to make the buzz go away. Disregard how it looks, but turn down brightness, color etc. to see if it makes a difference. Extreme levels in video have been known to cause audio artifacts. The results of this test will focus your investigation.

Chip