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On my Windows XP PC, there is a green line-out connection for jacks at both the back and the front. Is there any technical difference between both of these, or are the both effectively the same and the one at the front it purely there just for convenience?

For example, if I want to record from my PC to a tape recorder, does it make any difference if I plug the tape recorder into the back or front line-out?

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It depends entirely on your specific system. I’m guessing that you did not build the system, but it doesn’t really matter. Whether a system is custom built, assembled at a small computer shop, or by a large firm, it can be different because there is no universal standard to audio connectors.

In some systems, the front and read jacks are physically connected to the same connector (i.e., they act as a splitter). In other systems, they are connected to different ports on the motherboard. In others still, one or the other may not be connected at all. Vestigial connectors like this are common because generic cases could be used for a variety of models, some of which may have a certain connector be live while others don’t.

In general, when both are connected, as Ian said, the front is usually a stereo connector for headphones while the rear has surround-sound connectors for connecting to a receiver or external speakers.

As Ian suggested, you would have to either check the manual (if available) or simply try them both to find out what the case is for your particular system.

One thing to note however is that you may have multiple audio-adapters and/or devices in your system. For example, my rear audio connectors are from my sound-card while the front jacks connect to the onboard audio adapter. My motherboard also came with a cable to insert in the backplane that can connect to the board and has jacks for S/PDIF, MIDI, and Line-out. To test everything properly, I would need to make sure that something is playing on each device (e.g., both audio devices as well as wave, MIDI, CD, etc.) and that the volume settings are all correct. Otherwise, I could mistake something as not working simply because Windows plays all sounds through the default audio device unless I specifically select another one, or maybe the non-default just happens to be muted and I didn’t notice.

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I would definitely try and find either the sound card manual, or if the sound card is integrated into the motherboard, the motherboard manual. Only the manufacturer's documentation will tell you for sure, unless you want to post some more info about your PC.

In any case, the socket on the front is usually intended for headphones, while that on the back is more generally labeled "line out". In general, consumer grade line out sockets have fixed volume at -10 dbV pre-amp level, while headphone sockets are post-amplifier with variable volume adjustment.

My advice would be to try both and compare the results. For more serious applications I would always go with an outboard audio device simply because your average PC components are not made for anything other than casual use.

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Green is a typical indicator for speaker/headphone out, line out is a completely different thing and is often black. There is a difference to the type of signal that is sent out over line out versus speaker/headphone. – MaQleod Dec 3 '12 at 3:01
Thanks for your replies. My motherboard is a GeForce6100SM-M2, with on-board sound if this helps. On page 22 of the manual it says "F_AUDIO: Front Panel Audio Header (Optional). This header allows the user to install auxiliary front-orientated microphone and line-out ports for easier access.". So it looks like the front light-green jack is attached to a separate connector on the motherboard, and is still referred to as "line-out". – Goto10 Dec 5 '12 at 20:46

They should not be different. Two notes though:

  • On computers custom and some OEM computers the front panel lines are not hooked up. If you get a dead silence from the front panel, check this.
  • On some systemboards, if the front panel lines are connected, the backplane ones are automatically disabled (MSI has done this in the past). Check the board manual if you can't get sound out the back but everything software-wise is correct.
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