Headphones-out as line out

Pimpom

Member
2017-11-25 8:14 am
I sold my 55-inch TV, partly because it didn't have Headphone Out. I opened it and saw that it uses a small Class D amp with floating bridged outputs for both L and R, so there's no simple way to improvise an output with common ground.

I just bought a new 65-inch TV which does have HP out. It works with a normal pair of headphones. Can I assume that it's safe to connect it to an external amplifier with a common ground for L and R, that is, use the HP-out as an analog line out?

I know that, quality-wise, HP-out is not a good point to take out the sound. But I'd like to use it as a stop-gap measure until I get a proper system that's compatible with the HDMI-ARC output.
 
yes. it will work. It will also include volume control from the TV.


The option where no HO out is available is to plug in a DAC (optical or COAX in) which most TVs have these days. The subtlety here being that DAC outputs do not include volume control. Choose an external DAC with a remote volume control, there are some quite decent ones out there (by TV land standards) and you are good to go.
 

Samsara

Member
2011-05-30 5:15 pm
I can't think of a reason not to use the HP out as a line out.
TV use btl amp, the easy and cheap solution is car audio adapter
download.jpeg
 

Mooly

Administrator
Paid Member
2007-09-15 8:14 am
Some TV's have the headphone output configurable in the menus and it can be switched between fixed level line and normal headphone.

Also you might use (if it has one, many don't these days) the audio output from a Scart socket.
 

Samsara

Member
2011-05-30 5:15 pm
That's an interesting idea. But my TV has HP-out which works with a pair of headphones with a common ground, so it's fairly obvious that it doesn't use BTL amps. The TV is new so I don't want to void the warranty by opening it up to see.
My answer is about TV speakers output.
Of course, headphone output cannot be BTL, because Jack 3 contacts (only somes dedicated Headphones amplifiers have balanced output).
 
I just bought a new 65-inch TV which does have HP out. It works with a normal pair of headphones. Can I assume that it's safe to connect it to an external amplifier with a common ground for L and R, that is, use the HP-out as an analog line out?

Generally it is safe. If it uses a TRS output (i.e. 3 wires) it will feed an external amplifier through an adapter cord like THIS ONE There are also 1/4" versions available at about the same price.

The only precaution here is that sometimes the heaphone level can be a bit much for a line level amplifier. To adjust simply turn the amplifier's volume down a bit until you get no distortion and use the TV's volume control to adjust up to your max-level.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
...so it's fairly obvious that it doesn't use BTL amps. ...

With the low cost of small amps today, it seems obvious it could have 5W bridge amps for speakers +AND+ a 50mW common-ground amp for headphones.

In early days of laptops it was semi-common to find that the headphone shell was NOT "ground" but a 2.5V DC reference, avoiding two coupling caps (nobody cared if you had a couple Volts around your head). But these days "everything" uses the stereo-mini as a compact cheap interconnect, and I have seen cap-less headphone chips designed to let the shell be grounded.
 

Pimpom

Member
2017-11-25 8:14 am
Done it, and it works without any problem. The signal level is lower than I expected, compared to line level signals from other sources that I used to feed the same amplifier before. With the amplifier volume control at ~90% I have to turn the TV volume to 40-90% to fill the living room.

I've been in electronics for about half a century and did my share of component level designing and building of audio stuff before semi-retiring. My main concern was that I might be unaware of some new-fangled technique that could possibly harm the TV when connected this way.

Thanks for your interest and suggestions, everyone.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> The signal level is lower than I expected

With the general fall of headphone impedance, "normal" voltage at headphone jacks is lower. Today 0.25V in 32r is LOUD, and many headphone jacks won't make a lot more (particularly cellphones). Indeed you may need "all" your gain reserve to work into Hi-Fi inputs. Or dig out your old preamp "line stage" with its gain of 5 or 10. Or a one-stage booster.