It is possible to connect amplifier output of speakers to my PC?

Question

Can I connect the sound that was destinated to speakers from an amplifier to a PC sound card line-in? Won't my sound card burn? I don't have any other outputs on amplifier (line-out or headphones) and I don't have any other way to obtain that sound. Thanks

Answer 1

Plugging a powered / speaker output from an amplifier into a line-in jack will likely cause damage, plugging into a microphone input will cause permanent damage.

Many modern sound cards can deal with line-in and microphone signals using a single connector and a configuration option in the driver.

It is possible to turn down the volume, and connect the signal from an amplifier output to a line-level input, however, it will likely sound terrible.

• With a speaker connected, the signal will be distorted by the load from the speaker, the speaker's voice coil, and possibly other things.
• Without a speaker connected, the signal / voltage will likely be much higher, distorted due to the lack of load, and may permanently damage your equipment.

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There are three common audio level types, it's a very good idea to ensure that you match these between your equipment.

• High imepdance
  • Typically in the milivolt range, requires a pre-amp
  • e.g: electric guitar, some microphones, etc...
• Low impedance
  • Typically 1-2v peak, low-current source
  • e.g: line-level, headphones, some microphones, etc...
• Active
  • Typically in the 10s of Volts (or higher) fed into a low impedance sink (4Ω - 8Ω) with the ability to deliver considerable current
  • e.g: output of amplifier to speakers

Within each of these there are then a number of common ranges - for example, there is a substantial difference (+40%) between "Consumer Line-Level" and "Studio Line-Level".

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Equipment exists to convert between these levels, for example a "DI" (Direct Input) converts between line-level to high-impedance.

It's less common to convert powered / speaker outputs to line-level, but it is possible and will typically involve an audio transformer to put some load on the amplifier and also reduce the signal level. I've never seen a "real" name for these, but search for "High to Low Level Converter", and you'll probably come up with a product aimed at car audio. Be careful, as the cheaper options are often limited to a fairly low power (<15W).