Can I make a stereo headphone jack deliver a monaural signal?

[cazksboy]

This question may be so simple even a caveman could answer it - but I'm stumped! I did my due diligence with a search; I couldn't find anything related to my question.
I am a musician (I play electric bass) and I am trying to follow along with my instructor's lessons, in mp3 format. I have them loaded into my mp3 player, listening with a nice set of headphones. I realized that the lessons were mixed in the studio with the spoken vocal lesson in the left channel and the instructor's electric bass in the right channel. So essentially, the mp3's are mixed stereo even though all it is, is spoken word and electric bass.
My problem is that I am deaf in my left ear (born that way) so I can't hear anything coming out of the left headphone cup.
MY QUESTION: Is there a way I can rig some kind of adapter that will sum the left and right channels into a single monaural channel? That way I could hear all the material out of my good ear.
Before you ask, I know I could just use a boom box, but I prefer to use headphones - it just works better for me that way.
Thanks in advance,
...Doug

[Chuck H]

You should be able to find a stereo to mono adaptor plug at any Fry's, Radio Shack, Best Buy, Good Guys, etc.

Take your listening device with you when you shop. A stereo to mono plug may simply limit you to one side of the recording. You may need a stereo to mono plug AND a mono to stereo plug to get both audio channels on both sides.

[cazksboy]

You should be able to find a stereo to mono adaptor plug at any Fry's, Radio Shack, Best Buy, Good Guys, etc.

Take your listening device with you when you shop. A stereo to mono plug may simply limit you to one side of the recording. You may need a stereo to mono plug AND a mono to stereo plug to get both audio channels on both sides.

Thanks Chuck. I'll give that a try.

[oc disorder]

This should do the trick :-




Presume they are 3.5 mini jack plugs and sockets.
Great lack of a mono button on anything these days...!

I don't know what the impedance of your headphones are or how robust the mp3 players output is.

Rather than just short the two L&R together (where it wont matter which way you put the headphones on)
you are quite right that the two channels have to be summed.
2 tiny 10 ohm 1/4 resistors may fit in a 3.5 mm plug (pref. with a plastic cover) which should mix the two together
without straining the output stage too much.
Other idea is to buy 2 mini 3.5 sockets and mount them end to end in an old 35mm film container or similar
and wire the resistors in that.
Then you will need a mini 3.5 stereo jack to mini 3.5 stereo jack to plug between mp3 player and film container
making sure it plugs into the separate resistor to tip and sleeve mini jack.
Obviously the headphones then plug into the remaining jack in the film container.

If all fails write to Neil Young and request a mono button on his Pono player.

I can't see any other manufactures implementing this !

[Chuck H]

OC has a good point about the impedance. Lower impedance levels, like simply summing the load does, might be hard on the player if the resulting load impedance is too low and the player isn't robust. I'm a dinosaur and don't usually pay heed to the limitations of newer technology. In this light, OC's use of resistors for summing is a good idea. It will lower output, but that shouldn't be too much of a problem for these purposes and it will be a safer load for the player. It's more work though because it involves taking "S" apart, adding components, soldering and confirming circuit accuracy along the way.

Or you could just try the conversion jacks and see if anything acts funny or fails. Which is probably what "I" would do

I just wanted to acknowledge OC's "correctness" on the matter.

[g1]

A few comments about going the adaptor route.
It needs to be stereo plug to mono jack, not the other way around. (example 3.5mm Stereo Plug to 3.5mm Mono Jack Adaptor - Gold Plated - Monoprice.com).
Some circuits do not like having the 2 amps shorted together like that. If the output gets weak, don't use it. In that case you will need summing resistors like OC mentioned.
Using the adaptor, the mono output will now be only in the left headphone. Depending which side you need, you may need to flip the headphones around. With most types it won't matter, but some are designed to only fit one way and may feel funny if you flip them over.

[Chuck H]

It needs to be stereo plug to mono jack, not the other way around.

I though on that. But since the recording is also done in stereo I wondered if this might not omit one channel from the audio. That's why I mentioned that more than one adaptor in series may be necessary.

And it's good to note that amps don't like being summed together. I don't know how well newer products tolerate this. Older products didn't suffer failure liable circumstances. Usually. ie: there are mono to stereo and stereo to mono adaptor jacks Maybe best to just use the summing resistors as outlined by OC. That's certain to work without any issues.

[J M Fahey]

Agree and add: it will probably work with the 10 ohms resistors suggested, but I guess MP3 player out expect 32 ohms (nominal) headphones, so I'd raise them to 33 ohms, just to play it safer, and agree on stereo 3.5mm plug > resistors > stereo 3.5mm jack if used straight with headphones or 3.5mm plug > resistors > mono 6.3 mm plug if you go into some MP3/CD/Line in available in your practice amp (most do these days) or 3.5mm plug > resistors > dual male RCA (in parallal) if the practice amp has them (some do).
So you have all bases covered.

[cazksboy]

This should do the trick :-

[ATTACH=CONFIG]35763[/ATTACH]


Presume they are 3.5 mini jack plugs and sockets.
Great lack of a mono button on anything these days...!

I don't know what the impedance of your headphones are or how robust the mp3 players output is.

Rather than just short the two L&R together (where it wont matter which way you put the headphones on)
you are quite right that the two channels have to be summed.
2 tiny 10 ohm 1/4 resistors may fit in a 3.5 mm plug (pref. with a plastic cover) which should mix the two together
without straining the output stage too much.
Other idea is to buy 2 mini 3.5 sockets and mount them end to end in an old 35mm film container or similar
and wire the resistors in that.
Then you will need a mini 3.5 stereo jack to mini 3.5 stereo jack to plug between mp3 player and film container
making sure it plugs into the separate resistor to tip and sleeve mini jack.
Obviously the headphones then plug into the remaining jack in the film container.

If all fails write to Neil Young and request a mono button on his Pono player.

I can't see any other manufactures implementing this !

Hello OC, apologies for not responding earlier. THANKS so much for your advice, including an easy circuit diagram! That's EXACTLY what I am after. As to my headphone's impedance, they are an old pair of Sony MDR-7506 which still sound great - they are 63 ohms. My mp3 player is actually a cheesy-yet-effective Tascam GB-10 guitar/bass trainer....this one: Product: GB-10 | TASCAM
I wonder if the headphone impedance would influence the choice of resistors used? I'm guessing that the answer is yes...
Thanks,
...Doug in Arizona

[oc disorder]

Here's the specs of the output (+ new windows spelling!)

TASCAM GB-10

Analog output ratings/LINE OUT
Connector : 1/8” (3.5 mm) stereo mini
Output impedance: 23Ω
Nominal output level: –14 dBV (10 kΩ load)
Maximum output level: +2 dBV (10 kΩ load)
Maximum output: 15 mW + 15 mW (32Ω load)

Computer compatibility (page 96)
Widnows
Pentium 300 MHz or faster
128 MB or more memory
USB port (USB 2.0 recommend

And Juan's suggestion of 33ohms instead of 10 is a sensible cautious approach.
With your 64ohm headphones lets hope there is enough level for you to hear .. you could experiment with only one headphone connected
for your "good ear". i.e. Remove the bridge wire across the tip and ring in the socket.