Strange noise on line-in... Sample WAV attached.

GoldWave general discussions and community help
Post Reply
Vinyl
Posts: 6
Joined: Mon Dec 29, 2008 9:29 pm

Strange noise on line-in... Sample WAV attached.

Post by Vinyl »

Hi there everyone.
:)

While trying to perform line-in recording, I get this odd noise which I am unable to get rid of. It is random - not there all the time, but when it is, it spoils the master recording.

Please ignore the underlying 50Hz mains-hum, as I can get rid of this easily using the reduce hum filter in noise reduction, but if I apply it before sharing the file, it also filters some of the noise I want people to hear.

Does anyone know what this is, and more importantly, how I would go about getting rid of it?

Is there a filter I can apply in Goldwave to filter this out perhaps?

I only discovered this today, and have already completed more then 50% of the recording, and don't really fancy having to re-record everything, so I am very hopeful that there is a filter to get rid of this...

http://rapidshare.com/files/178010496/s ... oise-e.wav

The file is just shy of 2MB in size.
DewDude420
Posts: 1171
Joined: Fri Mar 11, 2005 11:15 pm
Location: Washington DC Metro Area
Contact:

Post by DewDude420 »

if i was to make a guess...that's GOT to be some kind of electrical interference. i can see the 50 hz mains (which is a switch since i'm used to 60 over here across the pond), i can see the scan rate from the monitor...but that stuff you don't really hear...your noise is interesting. I've never heard anything like it before nor have i ever seen anything like it. The wave follows the same pattern throughout it's duration, i've just never seen anything like it. Since you haven't really told me a whole lot about your setup, i can't really go much further. It could be odd interference from an internal sound card...it could be a part going bad somewhere in the audio path...a ground not making connection all the time...all i can suggest is try to pay attention to the external environment when you hear the noise and when it stops..maybe something electrical is kicking on...maybe some wireless device is coming through the analog path somewhere....I use a lot of analog gear and you'd be surprised what causes things to make strange noises.

as far as getting rid of it, it seems to be a low enough amplitude and repeative enough the noise reduction handles it ok. i've mixed your sample with some actual audio and tested this theory..although not to the extent i will as the evening continues.

*edit* noise reduction does ok IF your audio meets two conditions.

a) there isn't a lot of "delicate" audio below the amplitude of the hum
b) you're not trying to filter it out of something like a acoustic guitar track

the problem with trying to filter it out with a frequency filter is you'll just reduce the amplitude of what you want to keep and the mix will sound wrong.
Vinyl
Posts: 6
Joined: Mon Dec 29, 2008 9:29 pm

Post by Vinyl »

Yes, it certainly is odd, eh?

I have heard this before in my stereo and other audio gear not in this house, so it must be some form of RF noise perhaps?

I will try passing the audio leads from the turntable through a ferrite toroid core a few times, and will also pass the outgoing leads from the preamp/mixer through a core too to see if that helps dampen it out.

As you say, for all recording other then spoken-word or otherwise quiet passages, it is not really a problem as the level is well down on the main content. But it is annoying that it is there during the quiet recordings, and in those ones, it can be heard. I have done a few more recordings since I posted the first message, and the strange sound has not yet returned, but as I have heard this before in other sound equipment, I have no doubt it will most like reoccur. :(

A little background as to the setup:

- Standard computer with Realtek AC '97 soundcard
- Line-in selected as recording source within Goldwave
- System mixer has the likes of Synth, Mic and CD Player are at volume-zero and also have their MUTE boxes ticked.
- Sony Video Sound Effector XV-A33F used mainly as an audio-level mixer
- Kit-based RIAA Magnetic Cartridge pre-amp in diecast enclosure with external PSU to minimize mains-hum.
- JVC AL-E500 fully automatic turntable with moving-magnet cartridge

The turntable has a separate earth-drain wire which is screwed directly to the shielded case of the pre-amp. This produces excellent results with most records. There is a very small 50Hz hum pickup somewhere in the chain, but this does not worry me at all, as Goldwave's excellent suite of filters and tools allow me to easily remove the hum, so I don't even bother trying to prevent it, as it is only very marginal hum and is easily filtered out using NOISE REDUCTION/REDUCE HUM.

The Sony mixer is designed to add sound-effects etc to your home movies, but I only use the two main sliders as an AV mixer - one for the audio, and the other is the composite-video level, allowing me to fade to black or white for editing home movies, but in this case, only the audio slider is being used. The video slider is set to minimum and not used during audio work, naturally.
DewDude420
Posts: 1171
Joined: Fri Mar 11, 2005 11:15 pm
Location: Washington DC Metro Area
Contact:

Post by DewDude420 »

First thing I would do is get a seperate sound card. Onboard sound is poor.

Verify the shielding on your preamp is actually grounded...use an earth ground if you can get to it (for me its the screw that holds the gang plate on). Even if its grounded too much ground can't hurt unless you get a ground loop and get excess hum. That could be what that is but it's not very typical to make that kind of noise.
piano nick
Posts: 423
Joined: Wed Jun 16, 2004 8:33 pm

Post by piano nick »

First I'll make it clear that I am not an audio expert in any way.

I downloaded the file and maximized it a bit (to -10 dB), and I noticed three odd things.

1. The left channel is louder than the right.

2. Listening to the "wave file", it seems that the left channel is higher frequency than the right.

3. Both channels are not symmetrical about the neutral axes - I think this means there is a DC offset in both channels.

When I applied Effect/Offset/Scan Offset/OK, both channels were centred nicely about the neutral axes. This won't help removing the noise, but it may provide a clue as to what the problem is.

I agree with DewDude's comment about the soundcard. My soundcard is fairly high end and was pricey, but there are some pretty good Creative X-Fi cards at very reasonable prices.

I've spent a lot of time at PG Music forums, and this problem has never come up in six years that I can recall, but I don't know of anyone that is using an onboard soundcard either.

Glenn
Vinyl
Posts: 6
Joined: Mon Dec 29, 2008 9:29 pm

Post by Vinyl »

@ Piano Nick: (1) Yes it is, turntable or preamp has always been slightly unbalanced with respect to levels. This could be a fault of the cartridge, or it could be a mis-match in the preamp. In any event, it is not a problem for me, as once the source is recorded, the first step I perform is editing of only the right channel, where it is boosted by around 3dB, which evens out the level problem. (2) I have not noticed this myself. Sample-rate is 44.1 stereo, and I have plenty of recordings where the problem noise that is the subject of this thread is NOT present, and they sound perfectly even in terms of HF response as far as I am concerned, and I like things to sound of reasonable quality. (3) I have not noticed this either. It is likely that this comes from the source vinyl, as they often introduce crosstalk.

I will have a play with Effect/Offset/Scan Offset/OK to see what happens.

I've never really noticed any major improvement with special sound-cards over on-board for basic stuff. While it might not render broadcast-quality standards, I find on-board perfectly acceptable for backup of records and tapes, which generally speaking, don't have a fantastic frequency response anyway after a few plays(and all of mine have been played lots before I started backing them up!)

I used to have a SB Live 24-bit card in there, but in all honesty, could not tell the difference between recordings made with it, or the on-board sound with respect to backing up of vinyl, so I removed the card.

I THINK I have found the source of the problem. After some playing around, I found that with the noise present, I could essentially kill it by plugging in an RCA dummy-load to the video-input on my AV mixer. I suspect that perhaps a plain old stereo audio mixer might not have this problem. The sound would seem to be coming from perhaps some kind of slight instability or other oscillations generated within the video amplifier parts of the AV mixer. With the input(and output) terminated with 75-ohm resistors-inside-RCA plugs, the noise vanishes the moment I plug the plugs into the video path sockets. Seems like this is the root of the problem, but I will certainly post back again, if it reappears with the sockets in place - more to keep the forum informed then anything else, as those of you who have responded don't know what the noise is either!!! :P
DewDude420
Posts: 1171
Joined: Fri Mar 11, 2005 11:15 pm
Location: Washington DC Metro Area
Contact:

Post by DewDude420 »

onboard cards sound "ok" at best. the average naked ear won't be able to tell.

the largest problem with an onboard sound is that it's ONBOARD. they're generally unshielded and a LOT of times you will get pulsing feedback at a very faint level....like on my second PC with onboard sound you could basically hear the hard drive activity. not to mention they use the absolute cheapest codecs and outputs. you might say it sounds ok in your CD player, but often times even CD players use rather cheap stuff.

quality cards have gotten cheaper, and I'm very happy with a lot of the USB offerings now. they're affordable and, entirely OUTSIDE of your computer so there's less chance of feedback.

to be honest, not sure WHAT would cause that noise, but good to know a dummy load to the video plugs solved it....like i said, when dealing with analog, anything can make noise.
GoldWave Inc.
Site Admin
Posts: 4372
Joined: Wed Mar 10, 2004 6:43 pm
Location: St. John's, NL
Contact:

Post by GoldWave Inc. »

One method that sometimes helps to narrow things down is to unplug all the audio connections, start recording, then plug in one thing at a time. For built-in sound cards, you can get noise even when nothing is plugged in. Next, plug in just the cables. Damaged or long unshielded cables can pick up a lot of noise. Keep connecting things until you get the noise.

Chris
Post Reply