Where this noise comes from?

rodos1979 · Post by **rodos1979** » Tue Nov 19, 2002 7:59 pm

Hello!

I see a constant -82db noise floor on SoundForge monitor levels when I go to record, even though I dont have anything connected to my Pulsar's 1 analog input.
Is this normal? Is that what u see too?
If not, what could be causing it and what can I do to fix it?

Thank you

Post by **garyb** » Tue Nov 19, 2002 11:36 pm

everything electronic involves SOME noise...-82db doesn't sound too bad..it could probably be better with proper wiring and sheilding...the main thing is signal to noise.(you should have 90-110db signal to noise in a typical digital format,i.e.cd or dvd.)if the noise is inaudible even in the quietest passage,then everything's fine.if however there is a hum,then you have a ground loop...

i do see some level in pulsar and logic mixers when record is enabled or an input is active,i don't know what soundforge meters are referenced to so i don't know if that number (-82db) is excessive or not.i checked my copy of sf (an old one,v4.5)and the meters only go to -60.(db levels are not absolute levels, but instead are referenced to an arbitrary voltage.there are a few standard 0 points....)

[ This Message was edited by: garyb on 2002-11-19 23:53 ]

samplaire · Post by **samplaire** » Wed Nov 20, 2002 3:41 am

On 2002-11-19 23:36, garyb wrote:
you should have 90-110db signal to noise in a typical digital format,i.e.cd or dvd.

How is it possible? The S/N ratio is 94db minus lowest audiable noise comes from a device AFAIK (94db=1Pa). Perhaps you mean the dynamics?

I see a constant -82db noise floor on SoundForge monitor levels when I go to record

It can be wiring, it can be something involves your P1 inputs (there could be a mains wire somewhere near you your computer) - try to listen to the signal (noise) as loud as possible and if you can hear something like distortion - it's a digital noise (at the signal 'bottom' there are only 0s and 1s one by one switching like an electrical switch and even if it's vewry low level it is audiable). It can be covered with a dither.

I'm not completly sure about it... Correct me if I'm wrong

astroman · Post by **astroman** » Wed Nov 20, 2002 6:00 am

hi rodos,

nice to see you here

I have about the same value on an unconnected analog channel, and I'd consider it ok (on a Pulsar one), but in my case that wasn't always so.
Gary is absolutely right: the cabling and grounding has a severe effect on background noise, but sometimes it is hardly understandable.
Since I've mounted most stuff in one rack with common ground of the cases, those little background noises from the COMPUTER are completely gone.
Even with headphones full throttle on and an extra 24db gain on the inputs, though I haven't changed the computer at all

The meters on the Pulsar can be misleading: they don't measure continously but keep showing the top level until you reset them.
So every little glitch pushes the level up.
Depending on the gain of the that dba level changes accordingly.

cheers, Tom

Post by **garyb** » Wed Nov 20, 2002 12:27 pm

On 2002-11-20 03:41, samplaire wrote:
On 2002-11-19 23:36, garyb wrote:
you should have 90-110db signal to noise in a typical digital format,i.e.cd or dvd.
How is it possible? The S/N ratio is 94db minus lowest audiable noise comes from a device AFAIK (94db=1Pa). Perhaps you mean the dynamics?

yes, exactly.my pulsar inputs show a 92db noisefloor, about 90db s/n..another format MIGHT be better....i was just speaking generally.the dynamic range compared to the noisefloor= the signal to noise ratio as you say....

[ This Message was edited by: garyb on 2002-11-20 12:28 ]

rodos1979 · Post by **rodos1979** » Wed Nov 20, 2002 12:40 pm

Hello to all!

First of all thank you for replying.

I provide 2 links, in order for you to have a clear idea of what kind of problem it is and how it is produced.
The pulsarsettings.jpg file its a capture of a pulsar project (have a look in order to see the connection). Take into account that I have not anything plugged in my pulsar's analog source.
The pulsarnoise.zip file is a recording of ehm...noise

but it is amplified 2 times by 20db, so you can clearly hear what kind of noise it is. (96Khz, 24-bit, stereo)

And here are my new questions:
@samplaire: is this the kind of noise you are refering to?
@garyb: could you try making these connections and tell my what you read in yout SF monitoring levels please?
@astroman: how can I ground and shield my PC in order to avoid this electric noise? Do you know any link I could have a look at?

Basically, I am trying to make sure that there is nothing wrong with my beloved Pulsar1 in terms of hardware!

Thank you

http://www.geocities.com/rodos1979/

[ This Message was edited by: rodos1979 on 2002-11-20 12:58 ]

kensuguro · Post by **kensuguro** » Wed Nov 20, 2002 1:29 pm

I guessing there's definitely nothing wrong with the pulsar..
doubt there's anything wrong with that sort of noise floor either. But dunno.. I don't care too much about noise so it could just be personal taste.

samplaire · Post by **samplaire** » Wed Nov 20, 2002 4:19 pm

Hi rodos,
I disconnected all the gear (including cables) from my Pulsar 1 analog inputs and got different noise than yours (after normalising my noise sounded something like pure white noise and was deep below -82db). Soundforge monitor levels show SOMETHING but I'm not completly sure if it's true... About your noise: indeed it's affected by something from the outside (not too distant computer monitor, a power suply?) and it contains crackles, too. It can be graphics card, too. Try to make sure nothing affects the signal - place the computer as far as possible from your mains socket; disconnect all other cables from your pulsar 1 (including the analog outs) leaving a digital out connected to a dat or cd recorder - then try to record the noise and compare it with the previous one - if it's different - it means a ground loop - if it's the same... hmmm, I don't know

Herr Voigt · Post by **Herr Voigt** » Wed Nov 20, 2002 5:30 pm

Hi rodos,
I understand that you have the question, where does the noise come from. But you know (and all other Pulsarians) that you can't hear -82dB noise.
So I tell you something about a similar problem: I connected my 3 synths over an A/D-changer (Fostex VC-8) with the ADAT 1 of my Pulsar. Every synth produces a noise floor of about -78 dB. So I put 3 noise gates into my start project; so I am sure that Pulsar is clean from noise. I need a noise-free project because I have to record many tracks digital with a MD-Player. If I choose recording by "music sync" without gates, the player starts immediately recording. So the low noise floor can be very annoying for me.
The 3 gates are not very elegant but effective.
Cheers, Thomas

Post by **garyb** » Wed Nov 20, 2002 9:37 pm

i think that you're about 10db high as far as noise goes.it's probably workable,but you have some work to do as far as sheilding and or wiring.....can't really give you specifics as far as what to do but i would first ask if you have a small or cheap power supply...i also wonder if you have really optimized your computer for audio or if your machine is expected to do everything(edit pictures,connect to the internet,be a typewriter)..if you have a do-all machine you should make it dual boot..get rid of cracks if you have them......

astroman · Post by **astroman** » Wed Nov 20, 2002 10:49 pm

from that noisefloor example I'd say that everything's okay with the board.
Have you noticed the modulation of noise when those pulses appear ? That's what drives the meters up - the noise level itself is significantly lower, possibly for the difference Gary mentioned.
If you search the forums for 'ground loops' you should find a lot of information, and some deeply affecting tragedies.

cheers, Tom

rodos1979 · Post by **rodos1979** » Thu Nov 21, 2002 9:35 am

Hello to all

Thank you very much for your answers and your ideas. Well, from the things you have suggested, there can be many causes of this sort of noise floor with my setup.
I have an old PC, which is overloaded in terms of hardware (2 hd, 2 soundcards, scsi card, cd-rom, cd-r etc etc etc!) and a 300W PSU. My PC is physically exactly next to my monitor and there are all sorts of electricity cables running all over the place....Basically, a complete disaster!
My new DAW should be on its way, and I am going to re-position things in my room, so hopefully the noise will disappear.

I just hope that this setup that I currently have wont damage my Pulsar card...

Thank you

samplaire · Post by **samplaire** » Thu Nov 21, 2002 9:43 am

you could do worse - like putting your computer near a electricity plant

so don't worry!!!

rodos1979 · Post by **rodos1979** » Thu Nov 21, 2002 11:31 am

Hello again!

hmm....sounds like a good idea, samplaire!

Ok, I did a lot of testing and recording the past half an hour and found out the following:
The noise I get is not relevant to my analog out connections, neither to the status of my PC Monitor (on/off).
But it is indeed relevant to my analog in connections:
Case 1: nothing connected to my Pulsar's analog in. Soundforge levels show -86db, and the amplified recorded noise is just pure white noise, with no crackles whatsoever. (so, everything great

)
Case 2: My Behringer Eurorack MX602A (turned off, i.e. not connected to the mains) connected via RCAs to my Pulsar's analog in. Soundforge levels show -79db, and the amplified recorded noise has strong presence of the frequencies around 100,200,400, 800 and 1600Hz plus crackles. (most prominent freq:800Hz)
Case 3: My Behringer Eurorack MX602A (turned on, i.e. connected to the mains, but all channels and main out channel turned off) connected via RCAs to my Pulsar's analog in. Soundforge levels show -76db, and the amplified recorded noise is same as in case 2.
Further findings:
- the crackles found in the recording are exactly the sound my hard disk makes when it is being used.
- Greece's mains are at 50Hz, and by looking at the frequencies that are most prominent in the noise recording, it seems that there might be grounding issues.

Questions:
1) WHY this crackling noise happens ONLY when I have something connected to my Pulsar's analog in? Isn't that weird?
2) What could I do to make Pulsar not picking up the hard disk's noise?

Thank you

Post by **garyb** » Fri Nov 22, 2002 1:34 am

sounds like grounding issues for sure.(computer case and ps are most suspect)make sure that if both computer and mixer are grounded that they are not on different circuits.are you useing the plus/balanced version?if so you could lift the ground.you can get a hum eliminator(basically an audio isolation transformer)hosa makes a cheap useable one.

astroman · Post by **astroman** » Fri Nov 22, 2002 6:25 am

hi rodos,

to q1: groundloops are always wiered.
to q2: imho your best option on the harddisk would be to use a stronger powersupply.
Maybe someone can lend you one for testing (?)
why: if the disk's head move, the drive draws more current from the PS, which 'answers' with a regulation process. Your noise example is amplitude modulated which I'd interpret this way. But I don't know for shure of course.
Btw: Greece is a charming country with charming electricity an phone systems as well.
I'll always remember that thunderstorm in the middle of the night when all of a sudden all telephones of the area united to rrrring

Haven't been there for a while now and really miss it

cheers, Tom

Nestor · Post by **Nestor** » Fri Nov 22, 2002 10:37 am

I think the difference between a Pulsar and a Pulsar Plus is, among other thinks, that is quite lees noisy. I experience no noise at all. When I once did, it was cos I had some electric supplies near my system. You should have your system at about one meter of distance from other electric supplies if possible is.

rodos1979 · Post by **rodos1979** » Fri Nov 22, 2002 3:39 pm

Hello to all!

I ve got a normal Pulsar 1 (RCA connections).

On 2002-11-22 01:34, garyb wrote:
make sure that if both computer and mixer are grounded that they are not on different circuits

Do you mean if they are connected on to the same mains plug or what? 'Cause they are connected on different, but these two plugs -as all the plugs of all the appartments of the building where I live- share the same "ground".
After Tuesday I'll try my Pulsar card with my new DAW, which has a 400W PSU, I think it should be OK.
Do you think that if I connected all my gear on a good-quality UPS I would see any improvement in the audio signals and I would have less grounding problems? Or a UPS is a completely irrelevant thing?

Thank you

[ This Message was edited by: rodos1979 on 2002-11-22 15:42 ]

samplaire · Post by **samplaire** » Fri Nov 22, 2002 5:10 pm

On 2002-11-22 15:39, rodos1979 wrote:
But these two plugs -as all the plugs of all the appartments of the building where I live- share the same "ground".

How do you know it? Do all of your wall sockets share the same fuse? It's easy to try - connect any desk lamp to a socket then switch off your fuses one by one (but not while your computer is on!). If the lamp switches off then try with a electrician lamp (I don't know how to call it - the thing that looks like a screw driver and has got a bulb inside) all other sockets. Theis way you can be sure they share one phase. Are all of your sockets grounded?

Do you think that if I connected all my gear on a good-quality UPS I would see any improvement in the audio signals and I would have less grounding problems? Or a UPS is a completely irrelevant thing?

This has nothing to filter your mains AFAIK. Unless it is a 2 devices in one thing (ie. UPS and mains filter). I think the most important in your situation is to get rid of the HDD farts and (of course) the monitor should be as far as possible from the comp (the noise I heard from your wave was obviously caused by the monitor)

Vince Clarke · Post by **Vince Clarke** » Sat Nov 23, 2002 5:30 am

Unbalanced/unbalanced connectors.......

You have to consider the following. Are you using Unbalance or unbalanced connectors? The other main thing is the fact that the convertion of data takes place directly on the PCI card. This is unfortunate becouse it tends to draw noise from you computer. Some other things to check is you cables i have positive expiriences with the following cables: Monster, planet waves and reference.