1

I'm stumped on this one. My monitor has these cruddy un-amplified speakers that you can barely hear when there is any other sound in the room you are in. My solution was to wire an audio out jack to replace the speakers. Below is how I changed the wiring:

enter image description here

Before putting the final wiring in place I tested this configuration using my phone as the audio source connecting an aux cable with bare ends to the jack of the original cable, then plugging external speakers into the female port. Worked wonderfully. So i hook in the jack to the monitor, pack it all up, and play something on it. I get immense static over the speakers, and any volume past a certain point cuts out the audio altogether. My hunch is that twisting the two grounds together is what is causing this issue, but i'm not experienced enough with electronics to know how to resolve this.

Am I stuck with the original cruddy speakers, or is there a way to do this correctly?

EDIT: Also here is how I wired up the 3.5mm jack for referenceenter image description here:

EDIT 2: I have tried isolating one channel as others have suggested, this yielded the interesting result of preventing the cut-outs from audio peaks, but the intense static remained. I've also tried reversing what I assumed were left channel and ground, and that did not work.

I guess what I'm looking for most is that my logic with this correct? can you replace a stereo speaker output with an aux jack reliably? is this just a fringe result where it typically would be a success?

EDIT 3 (5-5-17):

Finally got a chance to wire it up how Trevor specified, still same issue, heavy static on the line through my amplified speakers, then I tried something that yielded an interesting result. in my frustration I figured I'd test the setup with a different speaker, just to see, but I only had a pair of headphones handy. I plug them in and nothing. Dead air. Through the speakers I get heavy static and distant speaking (no warble now that I've removed the two middle wires) but through the headphones I get dead silence. Maybe this is the clue that breaks the case?

Swizzler
  • 11
  • 1
  • 1
  • 3
  • 2
    Maybe the audio circuitry is even cruddier than the speakers. – Ignacio Vazquez-Abrams Apr 28 '17 at 01:26
  • 4
    Try hooking up only one channel to the jack. If that works well, you know that the speaker lines need to be isolated. – DoxyLover Apr 28 '17 at 01:42
  • 1
    Interesting result from this, The audio cut-outs that occurred went away but the intense static remained. I don't think the static is a shielding or speaker issue because when using an external source (like the phone) has no static. – Swizzler Apr 28 '17 at 03:07
  • 1
    Are you sure that what you're showing as ground really is ground? – Finbarr Apr 28 '17 at 05:50
  • Did you mount the audio jack in the housing of the television, or is it hanging loose? If you mounted the audiojack you might have created an unwanted connection to the true ground. It could also be that this ground connection is actually needed due to shitty design. – Crimson Apr 28 '17 at 14:50
  • Are the new speakers just speakers, or is there an amplifier in between? – Crimson Apr 28 '17 at 14:50
  • Crimson: I have tried mounting the audio jack in the monitor originally, but had the same thought as you and ran the wire out of the monitor and added the jack there. inside the monitor is the original cable that ran to the speakers using the original plug and socket on the board, so I haven't added any unnecessary variables there, all the added hardware is currently external. The speakers are new pc desktop speakers that I originally used to test the wire with, which tested and worked flawlessly so it's not an issue with the speakers themselves. – Swizzler Apr 28 '17 at 15:13

2 Answers2

3

You are assuming the speakers are driven with single phase and ground. That may be a BAD assumption. The speakers may be driven in push-pull mode.

See this cross post.

Try connecting ONLY the L, and R and find a different ground.

Trevor_G
  • 46,364
  • 8
  • 68
  • 151
  • I'll add this to the original post, but yeah Doxy asked this last night, and I did so, I isolated just the two wires going to the left channel speaker, and the peaking stopped, but the static remained. I wish I knew if they were true grounds or not, but I couldn't find a good wiring diagram of the monitor, I'm assuming they are because there are only two leads going to each speaker, so one would have to be ground. reversing the connection doesn't work either. – Swizzler Apr 28 '17 at 15:07
  • @Swizzler no, two wires does NOT mean one is ground... Speakers can be differentially driven – Trevor_G Apr 28 '17 at 15:11
  • So if that is the case, is there a way to wire it up to an aux jack or will I need a DAC or some logic in-between to make it work? Is there a way to determine what type of signal is outputting without use of something like a oscilloscope? – Swizzler Apr 28 '17 at 19:28
  • @Swizzler Get a speaker, wire one end to a known ground in the monitor. Perhaps the shield on one of the connectors. Then attach the other side to each wire on the internal speakers when sound is playing. If you hear sound, you know it is a driven line. Try it on all four monitor speaker wires. – Trevor_G Apr 28 '17 at 19:32
  • Okay, So I have done this and got some interesting results. I played audio wired to what I was assuming was ground as a control, then tried it connected to true ground with each of the 4 wires connected as a single channel, then later using them as left or right channel. Curiously it doesn't seem to care what cable is where, I get audio no matter the order that the cables are in (in some cases from the wrong speaker, but it's there.) I'm guessing thats what you were meaning, meaning it's a driven line. So is there a way to wire it up without having the latent static in the background? – Swizzler Apr 29 '17 at 02:21
  • @Swizzler yes, use one wire from each speaker, and use the true ground for the common. Then see that you get. If you still get static after that... I give up – Trevor_G Apr 29 '17 at 02:43
  • I don't know if it notifies you when I edit a comment but in case it doesn't: Finally got a chance to wire it up how Trevor specified, still same issue, heavy static on the line through my amplified speakers, then I tried something that yielded an interesting result. in my frustration I figured I'd test the setup with a different speaker, just to see, but I only had a pair of headphones handy. I plug them in and nothing. Dead air. Through the speakers I get heavy static and distant speaking (no warble now that I've removed the two middle wires) but through the headphones I get dead silence. – Swizzler May 06 '17 at 02:11
2

You are using speaker level signals into a device that expects line level inputs. Of course you are getting distortion or clipping or other issues. Your device is a full amplifier and speaker pair.

The simplest method here is tapping into the monitor's audio signal before any internal amplifier circuit. If its mic level, you will need a pre-amp before your external speakers. It is non-trivial to do, but not rocket science either. Look at the pcb and work backwards from the speaker connections. You will likely find an op-amp or dedicated audio amplifier IC that you can lookup and tap into.

Passerby
  • 72,580
  • 7
  • 90
  • 202