Can you help diagnose background beeping?

[klmonline]

This is unlikely to be a GoldWave problem, but this is a great community of knowledgeable people in the art and science of digital recording, so I am hoping you may be able to help.

I am recording on a Lenovo W520 laptop using an Audio Advantage Amigo plugged into a USB slot. The laptop has a solid state disk drive. I plug my Audio-Technica ATR-20 microphone into the Amigo input. I am using Windows 7.

Now for the symptoms. You will say I am crazy, but I have tested this extensively and it is repeatable and unvarying.

On a fresh boot of the computer, if I open GoldWave and create a new file to make a recording, everything is perfect. The playback is crisp, clean, and noise-free. But once I stop that recording and do a playback, any subsequent recordings have a beeping tone in the background. It is soft, but easily audible.

This happens whether I have the microphone plugged in or not, so it is not feedback between the mike and speakers. It is some kind of internal interference. I could understand if it happened on every recording... That would indicate that there is internal feedback in the recording hardware chain. But I am stumped by the fact that it does not happen on recording #1 of a fresh boot, and then shows up on all subsequent recordings (including if I hit "Undo" on the recording I just made and re-record in the same new file).

The tone is very regular - on for 0.5 sec, off for 0.5 sec. The Noise Reduction frequency graph shows that the tone is comprised of sharp spike frequencies at exactly 1k, 2k, 3k, 4k, 5k, 6k, 7k, 8k, 9k, 10k. Nothing in between.

It happens whether I have the microphone boost turned on or off in Windows. It is not present if I choose "Mute all" in the Control Properties menu for Master control on the microphone. But as soon as I set any volume for the microphone volume, it reappears.

UPDATE: I just installed Audacity to test record/playback in that. The first recording is clean and quiet. Subsequent recordings have the same 1k intervals tone, but it is constant rather than on-off-on.

Any ideas?

[DougDbug]

That's very strange... It might be an interaction between the mic and the interface.

Does it happen with the mic unplugged?

Your computer has a mic input, right? Have you tried it without the USB soundcard?

Computer mic inputs are "special". They supply a 5VDC "bias" voltage for an electret condenser mic. I think a dynamic mic like yours should work, but maybe not with that interface...

You might need to use a microphone specifically designed for computers.

frequencies at exactly 1k, 2k, 3k, 4k, 5k, 6k, 7k, 8k, 9k, 10k. Nothing in between.

I have no idea where it's coming from, but a triangle wave has odd & even harmonics, so it could be something like a 1kHz triangle wave.

BTW - Regular computer mic inputs are typically low-quality (noisy) and they just do not interface with "good" mics (low-impedance balanced connections). If you are trying to make high-quality recordings, you generally need a more-professional low-impedance mic with an XLR connector, and an interface with an XLR mic input. An alternative is a good USB mic such as the AT2020-USB. Or if your computer has line-in, you can use a mixer with a proper mic input.

[klmonline]

Thanks for your reply, Doug!

I do get the feedback even with the mike unplugged, making me think it is not an issue with the microphone's pickup and interference from outside noise. I use the Audio Advantage USB soundcard to get around that issue of the incredibly lousy microphone input jack on the laptop itself. Total garbage through that!

I have had my AT mike for so long that I don't even think they made a USB mike back then. Looks like I should try out a direct USB-connect mike and see if I can avoid the extra hardware in the signal path.

[DougDbug]

I do get the feedback even with the mike unplugged...

Maybe your Amigo interface is defective.

You didn't say how loud the "background" noise is, or what you're recording. It might actually be "normal" for this device... Every microphone preamp has some noise... If you are recording quiet sounds, or if you're getting a weak signal from this particular mic, you get a poor signal-to-noise ratio. When you boost the signal, you boost the noise too. i.e. If you are recording quiet nature sounds, or recording at a distance, noise is usually a problem. But, if somone is speaking or singing directly into the mic, noise is less of a problem.

[klmonline]

I have been using that Amigo soundcard for years without problems. Could be a new issue with it, but It's more likely a problem with my new laptop. The noise is low, but quite audible, whether there is true recorded signal on the track or not. I do straight voiceover recording and I cannot afford background distracting noises. This is definitely distracting! I record near-field and have a strong mike signal.

I'm going to purchase a new USB mike (either the Blue Yeti or the AT2020-USB) and see if I have better luck.

I do appreciate your continued contributions and thoughts. It's always good to bounce these thigns off another party.