Noisy without XLR connected

[KJThaDon]

Hi everyone, I have recently put together a little setup I am using to record vocals with. I have done some test vocals and getting "noises" while recording, even without the microphone connected to the mixer..

I am attaching a link to an mp3 recorded while the XLR was unplugged. I do have other background noises while the microphone is connected but that I know is because of the testing environment I am using right now. Computers etc.


This is what I have as of right now

Mixer/Interface: Peavey PV8 USB
Microphones (XLR): 2x AT2035 / 2x AT2020


Can someone please help me find the cause of this interference ?

Thank you!

soundcloud.com/kjthadon/back-noise

 

[ecc83]

Odd one this. I have run the noise thru Right Mark Analyser* and it is 1kHz at -80dB followed by every harmonic at about the same level i.e. 2,3,4 etc kHz. It sounds for all the world like the reversing warning on a truck!
Does it go it you plug in a shorted, pins 2 and 3 XLR?

I would send it but cannot get to grips with the attachement system! WHY can't these B forums all use the same setups!

Dave.

 

[gecko zzed]

I hear hiss and computer noise. If you had the gain turned up, that would explain the hiss. If you are using a laptop, that would explain, in part, the other noise.

 

[ecc83]

I hear hiss and computer noise. If you had the gain turned up, that would explain the hiss. If you are using a laptop, that would explain, in part, the other noise.

Indeed ^ What is needed is a recording where the gains are set for -18dBFS average with speech into a mic, 100mm from a 58 say, 300mm form a capacitor. then the mic unplugged abd everything left as is for another recording. Then lastly a recording with a shorted XLR (should strictly be terminated with 150-200 Ohms but only Grace 101 etc would show the diff!).

Dave.(24 bits of course!)

 

[KJThaDon]

View attachment err.mp3

Odd one this. I have run the noise thru Right Mark Analyser* and it is 1kHz at -80dB followed by every harmonic at about the same level i.e. 2,3,4 etc kHz. It sounds for all the world like the reversing warning on a truck!
Does it go it you plug in a shorted, pins 2 and 3 XLR?

I would send it but cannot get to grips with the attachement system! WHY can't these B forums all use the same setups!

Dave.

Thank you, I am quite confused myself.. I am not sure what you meant about the shorted pins? I have used a couple different cables now if you are referring to the XLR cables?

I hear hiss and computer noise. If you had the gain turned up, that would explain the hiss. If you are using a laptop, that would explain, in part, the other noise.

Thank you. I am using a desktop..With a microphone connected to the device, I could understand the hiss from background noise but that was with nothing connected..What do you mean by computer noise?
I have just done another recording with the gains all the way down, and no microphone connected again... it is attached..

Indeed ^ What is needed is a recording where the gains are set for -18dBFS average with speech into a mic, 100mm from a 58 say, 300mm form a capacitor. then the mic unplugged abd everything left as is for another recording. Then lastly a recording with a shorted XLR (should strictly be terminated with 150-200 Ohms but only Grace 101 etc would show the diff!). Dave.(24 bits of course!)

Thank you, but I am quite confused lol. I understand somewhat of the gain levels, which I have tried with all over the place but I do not know what you mean by "100mm from a 58 or 300mm form a capacitor?

I have bought 2 new XLR cables today from work, and they along with my old ones sound the same

 

[ecc83]

Morning K,
That is worse! The 1kHz component is only at -66dBFS and 2,3,4, kHz are in a decaying series, -70,-74,-76 and so on up to 10kHz when there is a sudden jump down that I can't explain. There is also a nasty rising LF response only 55dB down at 50Hz.
I am pretty sure however that the noises themselves are artifacts of the usb converter. These are usually very cheap 16bit affairs and not very good. To be fair to Peavey and others, you would be unlikley to make live recordings with such a low noise floor (the limit for 16 bits is~ -90dBFS but few 16bit usb systems are that good. My 24bit usb NI Ka6 on the other hand manages -101dBFS and no artifacts).

The mic/gain tests.
To judge the noise performance of a recording system you have to set the gains to a realistic level. Thus, the mixers channel level and master slider set to "0". EQ controls centre and pan the channel under test hard left. Set the (cap') mic up at 300mm from face and speak in a normal, conversational tone. Adjust the gain pot for -18dB on the computers DAW meters. Now some software is less than useful here because the meters are not numbered, Audacity has dB marks but Samplitude Silver has better ones (it also has a spectroscope in it and you can view your noise spectrum).

Now that you know the appropriate gain for -18dBFS, pull the mic out and run a short noise test recording.

Lastly, I strongly suspect that you have a gain mismatch in the WIN 7/usb setup. Peavey should be able to talk you thru the setup procedure but if they can't/won't. PM me (then I shall bill Peavey for my time!).

Even better, buy an M-A2496 soundcard and forget marginal 16 bit usb. With that card installed you should get better than -90dBFS and no noises!

Dave.

 

[PRHunt]

I wouldn't be too alarmed by preamp noise when no microphone is plugged in. In this state, the preamp is unterminated, and will tend to pick up all manner of noise. The way to check for noise inherent in the preamp is to use a XLR connector which has a resistor (as suggested, 150 to 200 ohm) soldered between pin 2 and 3.

If you don't experience the same noises when mic (or terminated XLR) is plugged in, then you likely don't have a problem.

Paul

 

[KJThaDon]

Morning K,
That is worse! The 1kHz component is only at -66dBFS and 2,3,4, kHz are in a decaying series, -70,-74,-76 and so on up to 10kHz when there is a sudden jump down that I can't explain. There is also a nasty rising LF response only 55dB down at 50Hz.
I am pretty sure however that the noises themselves are artifacts of the usb converter. These are usually very cheap 16bit affairs and not very good. To be fair to Peavey and others, you would be unlikley to make live recordings with such a low noise floor (the limit for 16 bits is~ -90dBFS but few 16bit usb systems are that good. My 24bit usb NI Ka6 on the other hand manages -101dBFS and no artifacts).

The mic/gain tests.
To judge the noise performance of a recording system you have to set the gains to a realistic level. Thus, the mixers channel level and master slider set to "0". EQ controls centre and pan the channel under test hard left. Set the (cap') mic up at 300mm from face and speak in a normal, conversational tone. Adjust the gain pot for -18dB on the computers DAW meters. Now some software is less than useful here because the meters are not numbered, Audacity has dB marks but Samplitude Silver has better ones (it also has a spectroscope in it and you can view your noise spectrum).

Now that you know the appropriate gain for -18dBFS, pull the mic out and run a short noise test recording.

Lastly, I strongly suspect that you have a gain mismatch in the WIN 7/usb setup. Peavey should be able to talk you thru the setup procedure but if they can't/won't. PM me (then I shall bill Peavey for my time!).

Even better, buy an M-A2496 soundcard and forget marginal 16 bit usb. With that card installed you should get better than -90dBFS and no noises!

Dave.

Thank you ecc! I will try the test shortly. Just one question. What do you mean by gain mismatch in win7/usb setup?

I am sure it is something I can check on, but I have no idea that there was such settings on win7.

I have a decent sound card, or at least I thought so.. It is this one us.store.creative.com/Creative-Sound-Blaster-XFi-Titanium-Fatal1ty/M/B0018EFGTM.htm

 

[gecko zzed]

That soundcard may be decent, but it is not what you would want to include in your recording process.

Instead, it is better to bypass it altogether. Instead, just do your playbacks through your Peavy USB interface. That becomes your sound card from now on. Hook your speakers up to that.

 

[ecc83]

Setting up your sound devices and their volumes for Voice Chat. (Windows Vista/7) - Battle.net Support
That ^ shows you how to get into the fiendishly complex Win 7 audio setup regime. Do not follow that procedure as is, rather look at it as telling you how to open the various sections and turn certain things on and off and set gains. Win 7 you see, "sees" a usb AI device as a "microphone" and gives it the appropriates gain whereas of course a usb AI needs only a fraction of that. This is the problem I had with my A&H ZED10FX.

But are you using usb?! Did I miss that Creative (not!) soundcard before? The SB cards are probably fine for gaming and playing back Yooootooob junk but are not generally recognaised as being much cop for serious sound recording. They tend to have too much latency and I am not even sure that they can run with ASIO drivers? One thing is for sure, they use those G'awful 1/8" jacks! Better cards e.g. M-A 2496 use RCA phonos and still better, M-A AP192 use balanced 1/4" jacks. Heck! that card does not even have MIDI and for ~$150 that is unforgiveable!

If, as I hope, you replace the S(of a)B card with better, run RevoUninstaller on its advanced setting to try to rid the computer of all the Creative crap. Then run Ccleaner and clean the Registry. But even so you will find SB junk files turning up all over the shop for months, the only surefire cure is a C drive format.

Dave.

 

[KJThaDon]

Thank you guys, I do not use the card for recording but only playback.. I use the usb for recording. I will checkout that link when I get home

 

[ecc83]

Thank you guys, I do not use the card for recording but only playback.. I use the usb for recording. I will checkout that link when I get home

So we still cannot tell if the noise and hum levels are the fault of the usb mixer or the soundcard?

Try a record and playback with one only at a time. I suspect the Creative will have the better noise performance, certainly if it can run at 24bits and be free of artifacts but I would still swop it for a 2496.

Dave.

 

[KJThaDon]

So we still cannot tell if the noise and hum levels are the fault of the usb mixer or the soundcard?

Try a record and playback with one only at a time. I suspect the Creative will have the better noise performance, certainly if it can run at 24bits and be free of artifacts but I would still swop it for a 2496.

Dave.

Thank you ecc, I have looked at the link you provided earlier. I did in fact know many of these things and they where all set correctly..

I do not use the microphone jack on the Creative sound card, since my mics are running XLR > Mixer > USB > PC

So I am not sure what you mean

Thank you

 

[ecc83]

Thank you ecc, I have looked at the link you provided earlier. I did in fact know many of these things and they where all set correctly..

I do not use the microphone jack on the Creative sound card, since my mics are running XLR > Mixer > USB > PC


So I am not sure what you mean

Thank you

What I mean is, you say you record vis usb but playback with the SB card?
So, are you RECORDING the noise or is it being "created" (!) on playback?

Actually the latter should not be the case. I presume you are exporting the recording as a .wav or MP3 and so the noise must only be due to the usb recording system.....DOH! Tis early still! Get an RCA to 1/8" jack lead (ugh!) and record directly into the SB card. If that improves the noise perfomance great.
Then Frisby the card and buy a 2496!

Dave.