Line level out from PC to Hi Fi

  m4p 11:52 21 Aug 2009

From reading around the subject I believe the output from most sound cards is speaker level, designed for PC speakers and headphones. I want to connect my PC to my Hi Fi, but I don't want to risk damaging anything if the volume were to be turned up too high on the PC. What I want is a sound card that has true line level output, perhaps a usb device as this might cut down on some of the noise/distortion from the PC. Can anyone suggest anything?

Many thanks!


  ambra4 13:26 21 Aug 2009

“I believe the output from most sound cards is speaker level, designed for PC speakers and headphones”

Sound Card Line out

The signal out of line out remains at a constant level, regardless of the current setting of the volume control.

You can connect recording equipment to line out and record the signal, without having to listen to it through the device's speaker, and without the loudness of the recording changing if you change the volume control setting of the device while you are recording.

The impedance is around 100 ohms, the voltage can reach 2 volts peak-to-peak with levels referenced to -10 dBV (300 mV) at 10k ohms, and frequency response of most modern equipment is advertised as 20Hz-20kHz

This impedance level is much higher than the usual 4 or 8 ohms of a speaker, such that a speaker connected to line out essentially short circuits the op-amp.

Even if the impedances would match, yielding the theoretical maximum power transfer of 50%, the power supplied through line out is not enough to drive a speaker.

This is why you must use a amplifer speaker system with a computer line out sound card

Connection the line out to your “Audo Aux Input” on the amplifer wil not damage the ampfifer

  m4p 17:32 21 Aug 2009

Thanks for the response, however I'm not sure if we're crossing our wires, so to speak.

All the sound cards I've come across (nothing expensive to be fair) refer to their 3.5mm output as 'line out', although I don't believe it is line level out, but speaker out, and if I plug this into my aux on my amp, I can change the volume through the hi fi speakers using the volume control on the computer, this shouldn't be the case if it's line level out should it?

Perhaps I've just misunderstood what you said...

Thanks again

  Stuartli 18:23 21 Aug 2009

You can certainly alter the sound level of the (green) 3.5mm socket's feed, which is normally used for the mono/stereo output to speakers or headphones, either using the computer's Volume control or that of the speakers or headphones being used, or a combination of both.

  ambra4 05:33 22 Aug 2009

Granted you can alter the sound level of the line out but it is best if you set the line out level to a

mid range level so that you do not overdrive the “Aux Audio Input” on the amplifer which will

cause the music to sound distorted

  DieSse 12:21 22 Aug 2009

"I don't believe it is line level out, but speaker out"

It isn't exactly either. It's around line out levels, though controllable for volume.

It's not speaker output in the normal sense, as it's not powerful enough to drive normal speakers - it need speakers with an amplifier in them (or a separate amp)

As above - you can treat it as line out for the purposes of feeding it into an amplifier line in. I do that many times with different amps - always works fine. You're exceedingly unlikely to damage an amplifier line in, as they're not particularly sensitive compared with, say, a turntable cartridge input. The worst you might get is a bit of overload, in which case turn the computer volume control down a bit (good advice above to set it to midway to start.)

  DieSse 12:27 22 Aug 2009

Also remember that sound files on a computer do not have a specified recording level, compared with a CD or LP for instance. The actual volume of sound may vary wildly depending on how and where it was transcribed. So even if there was a constant level line out, the volume of played files might vary wildly.

Bearing in mind many people use headphones, most of which have no volume control, there needs to be a volume controlled output for them.

The line out on the computer is therefore a compromise solution to suit the many needs to which it can be put.

In the circumstances it's actually quite a decent compromise.

  woodchip 15:01 22 Aug 2009

You should connect to the Speaker Socket as this is not amplified, and will not bust your speakers

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