Audacity Forum

Hi There, i'm having a issue with recording, I posted a while ago that when i recorded i got this random shipping sound when i listerned back to what ever i recorded, I've now sort of sorted that by buying a behringer ufo202, which is great i'm now using this with audacity but he only thing is now i'm getting a weriod noise constantly true the recording, i've added a sample for you to hear.

Thanks

Dan

That sounds like it might be the USB data stream. Do you have a bad connection? Can you try another USB port? You can get into trouble with USB equipment if the computer USB battery connection is "dirty" or noisy. That was the problem that an early version of this adapter had -- the iMic for Macs.

Make sure the audio connections are clean and secure, too.

Is that sample clip the actual level of the trash?

Koz

It's -54 or so. Too loud for quality recording. I wonder if mine does that.

Koz

By the way, this can also be an earth loop problem.

when your computer and your audio source both have an earth connection on their mains plug and then you connect both together with an audio cable the result typically sounds like this. we just recently observed this problem when a friend connected his laptop to the club soundsystem. especially cheap PC laptops have external power supplies with an earth pin on the mains plug.
if you disconnect the earth wire, your problem will be gone. CAUTION, I don't recommend this practice on a desktop machine as it could be lethal!

Hi guys thanks for all the info I'll give this all ago, and kos yeah that's the volume of the noise quite annoying when recording as you could imagine!!!

[quote="vinylivo"] cheap PC laptops have external power supplies with an earth pin on the mains plug.
if you disconnect the earth wire, your problem will be gone.

Hi, how can i check and also remove the earth pin

Cheers

Dan

Hi Dan,
you can check earth connection with a multimeter (diode tester or beeper mode). connect one test lead from the multimeter with the earth pin of the mains plug and the other with the shield/ground of your audio cable. the ground on the audio are the outer metal parts on RCA/phone/cinch cables or the shaft (not the tip or the ring) on jack (standard 1/4" or 3.5mm 'mini-jack).
if there is a short between the two, the multimeter should show very low 'Ohm' value or beep if there is a beeper option (which most multimeters have). you can get cheap mutilmeters for around 20 to 30 dollars or so in an electronics shop (like radio-shack etc)

if the mains plug is one of the directly moulded one (you can't open it) then you have to replace it with a plug from an electric supplier store that can be mounted manually. ask there which colour goes to which pin. there are too many different types that i can give you a full list. in europe the cable colours are green/yellow for earth (the one leave open to circumvent your problem), blue for neutral or return and brown for phase or live.

BE AWARE that you're not allowed to do this on a desktop computer with a metal case or you risk your life! seriously!

In this case you need to buy an isolation audio transformer box to open the earth loop!

btw, if you're using a laptop you can also run the computer from the battery by disconnecting the power supply. this is also an easy check if that's the problem source of your buzz 'sound'.

vinylivo wrote: if you're using a laptop you can also run the computer from the battery by disconnecting the power supply. this is also an easy check if that's the problem source of your buzz 'sound'.

This is the method that I would recommend.

In the UK, it is illegal to remove the Earth connection unless the device (the Power Supply Unit) is double insulated (Class 2 appliance). Class 2 appliances are always clearly marked as such and there is no Earth connection (even if the lead has an Earth wire it will not be connected). This may be different in other countries.

Cheers guys i'll give this a go tomorrow and get back, thanks again for your help!!

Dan

steve wrote:In the UK, it is illegal to remove the Earth connection unless the device (the Power Supply Unit) is double insulated (Class 2 appliance). Class 2 appliances are always clearly marked as such and there is no Earth connection (even if the lead has an Earth wire it will not be connected). This may be different in other countries.

You're right, it's illegal in most countries in the world. the same here in switzerland.
that's why I suggested finally running from the battery while recording.

it's really a pitty that most pc laptop don't have a class 2 external power supply, even if it wouldn't be too difficult for the manufacturers. luckily my macbook pro does have a double insulated (class 2) power adapter