i hate the smell of a popped cap in the morning....

But I love those things, 'specially the soda can sized ones. Just hook a power cord up to the terminals, plug it in, and it's fourth-of-july!

Decades ago I worked in a group charged with keeping a military communications system running. Integrated circuits had not yet made it into most of the racks of circuit boards.

The electrolytics were mil-speced, but a big power hit and resulting spikes could actually cause the positive voltage buss to go negative. You could hear the caps popping, and they would often leak electrolyte onto the circuit boards.

The solution was called the "Crowbar" project, and consisted very simply of physical relays that were held open until the voltage dropped below a certain level, at which time the relay would drop and short the power supply outputs. Crude but it worked.

I miss all those hours with a soldering iron.....

RalphM

I had a problem like this with my Presonus Firestudio Tube interface when I first got it. Turned out when opening a template all of the record inputs were "on." Of course 16 open recording inputs will make quite a bit of noise, especially if the gain is turned way up on a few of them.

I'm sure you've checked this but make sure no inputs are set to record with the gain cranked up.

- Mark

Mark, Windows isn't booted-up. This is an OFF computer. So therefore no need to check recording levels.

Grazie

I think that that particular penny finally dropped for John Meyer too. He was hoping that I had a device buzz. John, unfortunately, nothing so neat and "Grazie"-curable. This is kinda more fundamental?Well, actually I DID understand that, but was trying to find out if, by doing exactly what I suggested, you could isolate the problem, while the computer was on, by detecting from which part of the computer the problem was originating. Also, you keep saying that the computer isn't on, but has been pointed out several times, your computer is in standby and therefore in fact is not off. As you pointed out in one of your first posts, the sound fades out, after about five seconds, if you actually unplug the computer. I therefore highly recommend that you use the word "standby" instead of "off" in any further posts in order to avoid confusing other people who might try to respond.

So, if you did indeed perform the test I suggested, and as you un-muted each device, one at a time, while keeping ALL other devices muted and, while moving the volume up and down for that un-muted device, you did not hear any change in the hiss volume, then it appears to me that the sound is not originating in one of the connecting devices.

Then, if this is the case, since the hiss is only in one channel, that rules out the power supply because it feeds both channels. Also, since the rest of the computer appears to be working normally, this further exonerates the power supply. To me, the key piece of information is that the problem only happens in one channel. Given this, the advice given several times by several different people to buy, or find in another computer, a simple cheap sound card, plug that in, and defeat the soundcard on the motherboard seems like a very sensible and inexpensive step towards finding and then permanently fixing the problem.

Yes, John, the better word would be Standby. Plugged in, but not ON, as in booted-up.

John, your logic makes sense to me. I may have been restating the obvious, but this further observation of yours, that having ONE duff channel, AND that the PSU "appears" to be making the rest of the system function, now seems straightforward.

Tell me, as the PC is in STANDBY, how does the MOBO sound get an electrical feed? Doesn't it get it from the PSU directly? Is it not possible the instruction to go into standby is what I'm left with?

If I carry on using a separate card, how would the now defunct sound area on the MoBo effect my editing?

Grazie

The PSU only supplies bulk power to the mobo these days.
In Standby the mobo still has power, it has to so the BIOS can run. The BIOS is waiting and looking for inputs that tell it to power up the CPU etc to full power. The network interface and other sections are still running in standby. When the code that is running in standby in the BIOS detects say you pushing the power button it signals the PSU to enable all the power to the MOBO and wakes up the CPU.

The CPU itself is powered by very high current DC to DC switchmode power supplies on the mobo itself. They're supplying something around 1.5V at 100Amps. That's around the same amount of current the battery in your car has to supply to the starter motor to start your car.

Of course the amount of power the CPU needs depends on how hard it is working. At full load it needs a very stable supply of power, a very slight drop in voltage (under one tenth of a volt) can cause it to have a minor seizure.

Bob.

I agree that electrolytic capacitors failing in a power supply unit is very common but a capacitor failing in the audio signal path or low voltage circuitry is not. There is a distinct difference.
As others have mentioned earlier I would do the following:
1. Check/replace PSU
2. Check audio out with external sound card. MoBo may have a failure with DAC integrated circuit.

That's my $0.02
Chris

Tell me, as the PC is in STANDBY, how does the MOBO sound get an electrical feed? Doesn't it get it from the PSU directly?

Yes, direct from PSU - while the PSU seems to be asleep (standby), it does maintain a voltage out on one wire; when it senses a change on another wire it goes into full On mode. Your TV, Videorecorder etc. around the house all operate similar.

If I carry on using a separate card, how would the now defunct sound area on the MoBo effect my editing?

You can disable the MoBo sound in BIOS, and use separate card. Disabling onboard sound conveniently makes it invisible in all Windows & application menus. Just select the newer soundcard in your applications.

So, the thoughts are now for BOTH, MOBO-sound and PSU, yes?

Here's a further thought: What would be gained if I did a test of turning off the audio in the BIOS? What would it tell me?

Grazie

[i]"So, the thoughts are now for BOTH, MOBO-sound and PSU, yes?"[/]

No, if the PSU had gone bad pretty likely the whole PC would not work. The power supply on the mobo that supplies the CPU and other parts of the mobo is another matter.

One question though. The socket that you're plugging the headphones into, is that on the front of the case or on the back?

Bob.

Back.

Bob I read the input from others and I detected a hint of a bad PSU? No? Viz ChrisMN above?

Grazie

"Bob I read the input from others and I detected a hint of a bad PSU? No? Viz ChrisMN above?"

As I said, if a PSU died, smoke is common plus whole PC no workies.

Now that we've spoken and the symptom are clearer I'd say:

1) Power supply problems very unlikely cause. In standby current draw is so low a blown electrolytic is unlikely to cause problems in the audio circuits.

2) Problem seems almost certainly isolated to the audio section of the mobo. Buying a cheapish sound card would seem a good invesment to keep you going. Actually buying a *good* sound card might be an even better investment as you could continue to use it when you do upgrade your mobo / CPU.

Bob.

YEAH!!!

It was the MoBo Audio.

Slotting a New CreativeLabs Audio Card proved this to be the case. No crackle/hiss on Standby either. So that's gone. And testing in Vegas - OK.

Well, you guys n gals THANK YOU!!!!

Grazie

Alls well that ends well and you've even ended up with a better sound card. OK, maybe slightly better. I have to say that or the audio gods will be flaming me :)

Bob

Well £25 proves the fidelity of all the rest of the MoBo, if someone wants to offer up something more for a bit more dosh, please don't hesitate.

Grazie

" if someone wants to offer up something more for a bit more dosh, please don't hesitate."

A bit more doesn't buy you anything more, a LOT more does. My own opinion, if you're not using the sound card for recording, only monitoring and unless you've got decent monitors in a proper space, save your money.

Bob.

Tnx

G

Sorry I didn't look at this thread sooner Grazie.

Assuming you aren't using a two channel analog setup with the audio control center set up for 5.1 digital.............

Does your motherboard have RealteK HD Audio?

If so (I now you bought a soundcard to replace it), you could try the following (just for the heck of it):

1. Set input gain a little higher

2. Mute Line In and other inputs not being used. (I believe you already tried that). Mic input noise level has been a problem with Realtek Audio Manager. The analog inputs in particular are more susceptible to EMI from other components such as PS, etc.

3. Use optical out (if possible) instead of Analog Out (Red and White)

4. Go into Device / Advanced settings. Check "Separate all input jacks as independent input devices."

5. Under the Speaker Configuration tab, click "Speaker Fill" towards the middle bottom.

John

John, I got this horrid sound in STANDBY. Would your suggestion take this into account?

Grazie

Yes,

All drivers are loaded in Standby.

John

But the computer hasn't been switched ON yet, John? This I don't understand.....

Grazie