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I'm trying to use CD4051BCN chip to channel some speaker outputs from a computer. these chips handle analog voltages from +/-5V. What is the audio line max/min Voltage coming out of the desktop PC? I just need the audio line this is without any amplification.

Would it be better to use a series of relays with higher voltage/current ratings?

Thanks

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4 Answers

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I just measured the voltage from my smartphone headphone jack, which should be similar to what you'd get from a PC headphone jack. I got +/- 1.5v (3.0 volts peak to peak). This was not under controlled conditions with a known audio source. I would guess that the output could peak at higher than +/- 3v (6v peak to peak).

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sometimes it will go 24V in mine , where ground looping and leak current give you a shock. Sorry poor grounding... – sandun dhammika Aug 14 '12 at 20:10
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This voltage may vary due to application as well as the use of sound cards or on board power. The average power output should be 3 V RMS, so that speaker components may not blow up.

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Typically about half a volt for consumer audio, maybe up to 2 volts depending on your sound card. See Line Level

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In some cases [ not extreme cases] due to the ground looping it may get up to more than ~60V. So if you designing a system, where poor grounding and many places are grounded, and with different power sources, I HIGHLY recommend you to use a 1:1 transformer too.

This is called an isolation transformer. If your not using that, you better ready for >~60V.

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A simple DC blocking cap might suffice for most of those cases. Normally with audio stuff you would have one anyway. There are some cases where an isolation transformer would be justified, but those are super rare (I've never needed one, and I work in the pro-audio industry). – David Kessner Aug 14 '12 at 21:14
I made my post just because , when I touch my iron body of my desktop I could feel shock still. May be my cheap power supply. BTW, I'm not in audio industry, if you more sure on this I'll delete my post. – sandun dhammika Aug 14 '12 at 22:05
Your observations are consistent with switching AC/DC power supplies that do not have a safety ground on the AC side and have isolated outputs. For that reason your answer is useful to others, so don't delete it! Normally that leakage is not dangerous or bad, but does sometimes cause a buzzing in the audio. – David Kessner Aug 14 '12 at 22:08
sorry I'm from SL[+094], and ~230V using , and center was grounded on nearest power distribution transformer. @DavidKessner are you using DC wall power? I don't know isolation is a part of FCC rules. – sandun dhammika Aug 14 '12 at 22:08
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According to regulations in the US, a device must either have a safety ground (a.k.a. 3-prong AC plug) or have double insulation (an isolated power supply and other stuff). Almost every switching power supply with a 2-prong AC plug suffers from this to some extent. This includes my Dell laptop, my Apple brand iPod charger, and many others. – David Kessner Aug 14 '12 at 22:11

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