Getting high frequency hum 960 Hz......

C

cb56

New member
....When using my peavey mic through lexicon alpha into my PC computer ONLY when recording software is open Cubase 5LE or audacity.
When software is closed mic still works through lexicon alpha but hum is gone.
I bought a pro co cable thinking it might be a decent one but when I switched it out to a cheap chinese cable the hum is almost gone. The hum does record. When I switch the mic off the hum goes away. Tried disconnecting from power strip and plugged straight into wall, better through power strip). If I move the mic and/or the audio interface away from the computer, there is no change.

Do I need a better cord? Mic? or is it something else. Not made of money here so a $100 mic cable probably isn't in the budget.
cb

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UPDATE: Turning the monitor screen off does not help and using my clip on condensor mike (audio technics pro 30) plugged directly into TC helicon voiceplay (for phantom power) into lexicon alpha gets same results.
 
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Sounds like the Lexicon output (to the computer) is the cause. Is there a output volume control (maybe in the software)? This noise problem is often found in USB mixers (My Mackie ProFX12, for example) if the USB output volume is cranked too high.
 
Ok, another piece of info. This falls under the try everything heading.
Connected mic and mic cable to XLR tp 1/4 converter plug and plugged in channel one which is the instrument line in. NO NOISE! the mic signal is quieter but if I crank it I can get a good signal still with NO NOISE.
Ok you brainiacs :cool: this has to be a clue of some kind. Please help a dummy like me.
 
The higher frequency sound is EMF leakage from the computer. When the software is open, it probably kicks up the CPU. All computers leak EMF. The question is, why is it getting into your mike signal? It's not clear from your post -- were you using an unbalanced line to connect the mike to the interface? If so, that's the problem. Also, the mike input on the interface will have a preamp circuit that the line input does not have. It may be either a defective interface or just poor engineering. However, the preamp will, of course, amplify any EMF incursions that are present, which is why you may here it in the mike input, but not the line input. The first place to start would be to make sure you're using only balanced lines for all inputs. You also might try re-positioning the mike, the cables and the interface to see if the noise changes or goes away.
 
using a standard xlr mic cable (is that a balanced cable?) into the xlr mic input on back of the unit.
The first thing I tried was repositioning everything as far away from computer as possible.
Thanks for responding.
 
Next step might be trying this on a different computer

This is a new computer that has the computer and monitor in the same housing. I think it’s called a Dell Inspiron all in one computer
 
This is very strange. I'd be inclined to think something is broken somewhere, though I'd be surprised if it's the computer. You might try opening up the computer, reseating all the cards and making sure all the cables are tightly plugged. Something is radiating EMF somewhere and too much dust in the wrong place combined with a partially open connection might be a cause.
 
No sign of a noise on the spectrum of that intro?

Dave.
 

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cb56 said:
Dave I don't understand what you are saying to me.
Click to expand...
Ok. Well I recorded that clip. Chopped out the intro and ran it thru Right Mark spectrum analyser (free btw)
Just looks like a normal ambient noise spec' to me.

Dave.
 
So your saying it's just amplifying a noise heard in my studio?
You do agree that there is a high pitched hum about 960Hz on the recording right.
I don't hear that noise anywhere other than in my headphones when I have the mic turned on and have recording software opened.
If the mic was just picking up room noise, wouldn't I hear it in the headphones when I am listening to the mic output from the lexicon with no software running. I can hear mt voice in the mic at that time but no 960hum.
Sorry if I'm missing your point or something. Still trying to learn.

I could make a longer recording of it if that would help.
 
Ok, took the Lexicon Alpha to another computer, installed the software and exact same problem. So it's not my computer.

More info:
The Inspiron is the computer I have been using. I took the Lexicon Alpha to another computer, installed the software and exact same problem. So it's not my computer.
I’ve tried 3 different mics no difference and 3 different mic cables no difference.
BUT, I discovered that if I unhook the mic from the cable but leave the cable plugged in I still have the noise. If I then unplug the mic cable the noise stops.
Could it be the mic cable? It’s a pro co dynamic 224s made in USA . Cost about $20 for 10ft cable.
I really don’t want to buy a super expensive cable unless I know that’s the problem.
 
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"You do agree that there is a high pitched hum about 960Hz on the recording right."

Not from my evidence. How can you be so precise about the frequency?

In any case I think I have a reason if not a solution. The Alpha's front end is picking up RF, probably as a common mode signal on the shield, no cable, no RFI.

The only simple, cheap dirty solution that comes to mind is to wind the cable around some clip on ferrites. Better would be to take the XLR off and wind the cable around two stacked ferrite rings. You could try asking the AI man'fctrs if they have had any RFI issues? Might be a mod. But then you might live in an area of particularly high RF field strength.

Try a mixer front of the Alpha.
Try another AI.

I grew up fixing transistor kit with RFI woes (valves tend not to give a ***t) because I live within a few clicks of Rugby and Daventry.
http://www.maplin.co.uk/clip-on-ferrites-32799

Dave.
 
ecc83 said:
....How can you be so precise about the frequency?

....
Click to expand...
To my ears, the pitch is close to the note B maybe slightly flat. Past experience tells me that a 60 cyle hum is also close to the note B (slightly flat) but in a much lower octave. 60, 120 240, 480, 960. Hey 960 is 4 octaves up from 60 cycle.

Enter 960Hz in this tone generator Online Tone Generator - Free, Simple and Easy to Use. and that's the tone I'm hearing. Hey I might be off by a couple Hz but it's real close.

Just looked it up.
Bb= 923.330 Hz
B= 987.770 Hz
So I think I'm in the ballpark anyway.
 
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cb56 said:
To my ears, the pitch is close to the note B maybe slightly flat. Past experience tells me that a 60 cyle hum is also close to the note by (slightly flat) but in a much lower octave. 60, 120 240, 480, 960. Hey 960 is 4 octaves up from 60 cycle.

Enter 960Hz in this tone generator Online Tone Generator - Free, Simple and Easy to Use. and that's the tone I'm hearing. Hey I might be off by a coupleHz but it's real close.
Click to expand...

Oh! I've got six ways till Christmas to generate tones! Including an old Heathkit valved oscillator! I was just curious.

Just for the craic, download and record your own clip and see if the tone is still there?

Dave.
 
Are you sure you are not just hearing a feedback loop? Are you listening with monitor speakers while mic is plugged in?
 
Jimmys69, you don't hear it either?
Doesn't matter if I listen to it with headphones or monitors. Mic on off or unplugged it's there.
BUT if you guys can't hear it or even see it on an analyzer, (and I trust your experience in these matters) Maybe I should just ignore it.
 
I'm going to buy a better mic cable balanced braided sheild in hopes that it will eliminate this (or find a good shrink)
question: What is quad connector? I assume 4 pins on the xlr. can I use those with my regular mic and lexicon (3 pin) or is this a specialty item?
 
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