Microphone humming when connected to preamp- grounding problem?

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easlern

easlern

Boredom artist
Hi all- I admit I know nothing about electricity except that you shouldn't touch it and you shouldn't get it near water. ;)
I just got a Presonus tube preamp for use with my mic, a Seinhesser(sp?) 816e, but there's a problem with it. When I run the mic through it, I get a terrible humming that gets worse when I touch the metal part of the microphone. I'm pretty sure this is a grounding problem, since I'm using an XLR->1/4" cord from mic to preamp and a 1/4" cord from preamp to sound card (X-Fi Platinum, in case that's useful info). (The preamp has one XLR and one 1/4" inputs, and one "balanced" XLR and one "unbalanced" 1/4" outputs.) I haven't tried using the "balanced" output because I don't have an XLR->XLR cord, but I don't see how that would help, since the preamp seems to be ungrounded anyway.
Assuming this is a grounding problem, I'm not sure what to do because my card doesn't have an XLR input and the preamp itself uses a standard 2-prong (ungrounded) AC-adapter. Are there preamps I can get that take an XLR input and output a grounded 1/4"? Is it possible I can take a metal wire and tape it to both the microphone body and a metal part of the computer? Maybe the problem has nothing to do with "grounding" at all? Maybe I am hopelessly ignorant of electricity and should stick to acoustics?
 
easlern said:
Hi all- I admit I know nothing about electricity except that you shouldn't touch it and you shouldn't get it near water. ;)
I just got a Presonus tube preamp for use with my mic, a Seinhesser(sp?) 816e, but there's a problem with it. When I run the mic through it, I get a terrible humming that gets worse when I touch the metal part of the microphone. I'm pretty sure this is a grounding problem, since I'm using an XLR->1/4" cord from mic to preamp and a 1/4" cord from preamp to sound card (X-Fi Platinum, in case that's useful info). (The preamp has one XLR and one 1/4" inputs, and one "balanced" XLR and one "unbalanced" 1/4" outputs.) I haven't tried using the "balanced" output because I don't have an XLR->XLR cord, but I don't see how that would help, since the preamp seems to be ungrounded anyway.
Assuming this is a grounding problem, I'm not sure what to do because my card doesn't have an XLR input and the preamp itself uses a standard 2-prong (ungrounded) AC-adapter. Are there preamps I can get that take an XLR input and output a grounded 1/4"? Is it possible I can take a metal wire and tape it to both the microphone body and a metal part of the computer? Maybe the problem has nothing to do with "grounding" at all? Maybe I am hopelessly ignorant of electricity and should stick to acoustics?
Click to expand...

To start with I would connect the microphone to the preamp with an
XLR->XLR cable. Then I would connect the preamp output to the sound card via a TRS(balanced 1/4")->TRS cable.
 
If RAK knew anything he would have also pointed out that using an unshielded soundcard on a computer introduces noise into the audio chain. He is right about the cabling though. Good work RAK.
 
jimmy2sticks said:
If RAK knew anything he would have also pointed out that using an unshielded soundcard on a computer introduces noise into the audio chain. He is right about the cabling though. Good work RAK.
Click to expand...


Well of course I knew that, I was just testing you. You passed. Didn't want to take all the glory for myself you know. Good work jimmy2sticks.
 
Thanks for the input guys!
I would blame the card except that direct input from my acoustic/electric guitar (in the same 1/4" input) has no audible noise at all. The microphone noise is not just the usual low-fi hiss either- it sounds kind of like one of those electrical arc machines you see in old horror movies. As it is, direct input to the sound card sounds better than with the preamp (I'm new to this, but I'm pretty sure it should be the other way around.) :P
I got a XLR->XLR cord and a XLR->balanced 1/4" (thanks for pointing out the difference, RAK) Monster Cable to see if I can get the noise under control. They assured me if it didn't work I could take them and the preamp back for a refund. I'm also going to try the guitar through the preamp, just to make sure I didn't get a bum unit.
I'll let you know how it all goes. . .
 
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I just today had something similar. I have
a minidisc plugged into AC (rather than
battery operated) and when I touch the
body of the mic there is a noticeable
hum in the audio. Not sure yet but I'm thinking
that this may have to do with in being
connected to AC. I did notice that if
I moved the minidisc -- such as picking
it up off a table/computer case, that
the humming would stop, if I was just
holding the MD in my hand,
so maybe some type of isolation would
help.
 
The Monster Cable definitely helps when I use it for direct input, but the sales guy gave me a cord other than an XLR->XLR so that test will have to wait. :P
When I get some time tomorrow I'll try the guitar through the preamp.
 
rak doesnt no shit about mics... psh so what if he works for shure...


;)

but its probably something to do with the xlr-1/4. i hate them, you really lose so much quality its not even funny.

why would you use that cable if you are able to use a regular xlr-xlr??
 
TragikRemix said:
rak doesnt no shit about mics... psh so what if he works for shure...


;)

but its probably something to do with the xlr-1/4. i hate them, you really lose so much quality its not even funny.

why would you use that cable if you are able to use a regular xlr-xlr??
Click to expand...


Where is that coming from? We're not even talking about mics here.

All things being equal XLR->TRS should be no different than XLR-XLR.

And I didn't always work for Shure you know.
 
$.25

hey jimmy dont let em fuck with ya... but i have been meaning to ask you that is "howard einstein" right????
 
XLR -> TRS is no different than XLR -> XLR. Both provide a balanced audio signal.

I would guess the 1/4 cable he is using between the pre and the soundcard is not a TRS cable.

As for the XLR -> 1/4, there should be no issues as long as the 1/4 end is a TRS plug.
 
tnjazz said:
XLR -> TRS is no different than XLR -> XLR. Both provide a balanced audio signal.

I would guess the 1/4 cable he is using between the pre and the soundcard is not a TRS cable.

As for the XLR -> 1/4, there should be no issues as long as the 1/4 end is a TRS plug.
Click to expand...

That's what I was saying. He said he ended up getting an
XLR->balanced 1/4" inch.
 
Okay, I got the cable. Here's how it is:
Microphone->XLR->XLR->preamp
preamp->XLR->TRS->soundcard input
The hum is completely gone and the mic sounds 100 times better than using direct input. I'm very pleased with this preamp. :)
Thanks for your input, guys.
 
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