[Subsonic]

What I'm trying to do is to make an adapter that will let me use my cans with my tv (doesnt' have a headphone jack). I don't have a preamp, headphone amp, or a amp that I could hook it up to either

. So instead of buying a DSP 360 or any other sort of amp, I think making something would be a good learning experience. My idea is to run the adapter off the left and right speaker outputs and wire it someway so that I can either turn off the speakers and listen thru my cans or leave the speakers on and still listen to my cans. Would this diagram work? How can I wire it so that I can use one switch instead of two to turn off both L an R outputs?

 

[Budgie]

Looks like your on the right path. You may need to add a series resistor to the headphone output to drop the level, but you might be fine without it. It will depend on your headphones and tv. If your phones are to loud, add a 100 ohm resistor to the left and the right positive, feeding the headphone. When you use the tv speakers, unplug the headphones to prevent overdriving them accidently.

 

[Subsonic]

That's good to know

. Is there such a switch that will let me turn off both the left and right outputs or do I have to use 2 switchs? I think my Senn. 570's need a lot of power to run them right so I'll try without a resistor.

 

[Budgie]

Just get a double pole switch. It is two switches in one package.
They are usually labeled as DPDT or similer. (Double Pole Double Throw)

 

[Subsonic]

That's what I though, I always get confused when it comes to DPDT, SPST,SPDT,etc... Thanks.

 

[Budgie]

Ya Betcha!

 

[CaptBubba]

Are the speaker output you are referring to RCA outputs? If they are then they probably will not have enought power to drive the headphones directly. You may need to build a simple amp (a Cmoy for example) to drive the phones if that is the case....

 

[Subsonic]

Quote:

Originally posted by CaptBubba Are the speaker output you are referring to RCA outputs? If they are then they probably will not have enought power to drive the headphones directly. You may need to build a simple amp (a Cmoy for example) to drive the phones if that is the case....

Nope, they're running off the speaker terminals on my tv. Only thing left for me to do now is to drill the holes in the enclosure and solder on the switch which leads me to the next question. Which terminals on the DPDT switch do I solder the left and right output to?

Are the terminals like this?
on off on ->R
on off on ->L

 

[Budgie]

The switch is like this:
on-common-on
on-common-on

Iwould wire it like this:
Speaker+ Right - TV +right - Headphone+ right
Speaker+ Left - TV+ Left - Headphone+ left
(Speakers on) ------------- (Headphones on)

The grounds for each channel will all connect together in two groups -left and right. In other words, do not hook the right and left grounds together, but all the lefts go together and all the rights go together.

Did I say that so that it makes sense?

 

[Subsonic]

Budgie, thanks again for the info. I finished the box yesterday and it seems to work fine (I do hear a hiss though). The way I wired everthing is that I wired the Right and Left input to the corrosponding terminal on the minijack and then I spliced the R&L grounds and then wired it to the mini-jack. The way I wired the switch is that I ran another set of wires running from the R & L tabs of the speaker tabs to the switch and then to the output tab. In other words, I did it according to the diagram I drew.

Is the way I wired the grounded the circuit correct? I'm hearing a faint hissing noise so I think I might have gotten it wrong. I think I should have left the jack ungrounded and just connected the R.in & R.out ground together and the L.in & L.out ground together. Right?

 

[Subsonic]

Would this be the correct way?

 

[Budgie]

Circuit two looks right to me. I suspect that the hiss is coming from the tv set itself and I doubt if you can solve it. You probably are only noticing it now because your ears are now right up against the speakers, so to speak. Unfortuneatly, most tv's are designed with very little attention to sound quality and a little hiss is not uncommon. I have added jacks to two tv's and they both have hiss.

Circuit 3 looks like it is missing the ground connection.

(I don't seem to have any way to draw a schematic easily.)

 

[Subsonic]

In circuit 2, I thought you said i shouldn't have the R&L ground wired together.

In circuit 3, how should I wire the ground for the jack?

The box is wired according to circuit 2 and it works.
The hiss isn't that noticable and as you said it's probably the tv so I'm not worried about that. I'm just trying to find out the proper way to ground the circuit.

Thanks again.

 

[Budgie]

The only concern I had with the grounds is some amplifiers will blow if the left ground and the right ground get connected together. But I realise now that is not likely a problem for a tv set and you would have to rewire your headphones to seperate the grounds, so I would say that that comment was probalby usless.