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Mike Sommer
A Hundred Dozen
Joined: 05 May 2008
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Location: Boss Angeles
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 Posted: Sun Aug 29, 2010 12:38 pm Post subject: Re: re: |
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| tokyofan wrote: | | The power strips have six 3-pronged sockets each...but can be plugged directly into the wall with 2 prongs. Hm. |
Are these power strips surge protectors?
| Quote: | Still puzzling why the MXLs don't hum with the USB pres but do with my set-up. I'll play around more with the cables, connections and see if it changes anything.
Thx! |
The USB pre uses the DC power from the computer. Sometimes this alone can bring about it's own set of problems, especially with laptop computers.
For audio equipment having a grounding system is very important; whether you are grounding the audio chain or grounding the power supply. If it's possible talk to an engineer at a local studio and find out how they deal with the problem.
I don't know it this is posible but you may be able to use a ground lift adapter:
 This uses the buildings conduit as the ground. It's not the best way but it is possible.
You can also use a power conditioner, that scrubs the power. Furman makes a few, but you need a grounding system here too.
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong. |
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tokyofan
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Joined: 13 Mar 2006
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Location: Tokyo, Japan
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| Posted: Mon Aug 30, 2010 4:29 pm Post subject: re: |
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This in from MXL:
| Quote: | Two issues I would ask is if he has a cable with pin 3 hot instead of pin two?
Has he changed the cables from the mic and RME to a newer set?
Some of the earlier models from Neumann were pin three hot and not the std pin two- I rarely have had this problem but it is a real possibility- How old are his Neumann's? |
Not sure what I should be checking here. Don't really know the difference between pin 3 hot and pin 2 cables. The Neumanns are around five years old...
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Mike Sommer
A Hundred Dozen
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Posts: 1222
Location: Boss Angeles
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| Posted: Mon Aug 30, 2010 5:09 pm Post subject: |
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Pin 1 Chassis ground (cable shield)
Pin 2 Positive polarity terminal ("hot")
Pin 3 Return terminal ("cold")
What they are trying to say is that the older U87 had their "Hot" and "Cold" pins reversed. Very Rare. (Some folks made up a special cable for their U87's. Or they would just switch it at the mic pins, with a little re-soldering.
Then they want to know if you changed all your XLR cables between all the components of your signal cain. In other words: new cable from the Mic to the Preamp, and from the Preamp to the Interface.
(To save a few dollars get some new, short XLR cables and see if the hum goes away.)
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong. |
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tokyofan
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| Posted: Mon Aug 30, 2010 5:31 pm Post subject: re: |
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Thanks, Mike! I'm getting quite the education!
So, newer XLR cables should work better with the MXL and U87? How do I know if my current cable is obsolete or incompatible? Is there anything on newer cables that look different?
I did try the Kiwi Blue quad cable from the mic to the pre and same hum...and then used my regular Canare cable from mic to the pre and the Kiwi between the pre and RME and same hum. Hm.
So, you're suggesting buying new, short cables to see if it fixes things?
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Mike Sommer
A Hundred Dozen
Joined: 05 May 2008
Posts: 1222
Location: Boss Angeles
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| Posted: Mon Aug 30, 2010 6:54 pm Post subject: Re: re: |
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| Quote: | | So, newer XLR cables should work better with the MXL and U87? How do I know if my current cable is obsolete or incompatible? Is there anything on newer cables that look different? |
Hold on... You are getting confused.
What I'm saying is that your cables are wired correctly. It was with the very early U87's, that the pins switched around. You have a newer U87 and a TLM103, and everything works with both. So you are good to go.
| Quote: | I did try the Kiwi Blue quad cable from the mic to the pre and same hum...and then used my regular Canare cable from mic to the pre and the Kiwi between the pre and RME and same hum. Hm.
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Now that sucks. I don't know what else you can do.
You could try taking a wire and an alligator clip and clipping one end to bare metal on the preamp Chassis and the other end to a metal water line to see if it magically goes away, if it does, it is indeed an electrical grounding problem. And try the same thing with the mic- between mic an the preamp and between the mic and the a water line.
| Quote: | | So, you're suggesting buying new, short cables to see if it fixes things |
Right. By keeping the runs short, especially between the Preamp and the Interface it is not only cheaper but is a smart play.
Because this sounds like a 50Hz hum I'm quite sure this is an electrical problem. Locate a different outlet on a different circuit and try plugging the preamp into that.
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong. |
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tokyofan
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Location: Tokyo, Japan
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| Posted: Tue Aug 31, 2010 2:03 am Post subject: re: |
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Sorry for the confusion, Mike. Right, I have the modern Neumanns using regular cables.
The mic cable is probably 25 ft from the booth to the Speck. The XLR-TRS cable between the Speck and AD-2 is very short.
I tried plugging the Speck into an outlet in an adjacent room (hopefully on another circuit) and still get hum. Should I do the same with the AD-2? I don't have alligator clips on hand.
Even if we eventually discern it's a grounding issue I'm not sure what I can really do about it. It might be more hassle than it's worth...and the Neumanns work fine as is.
Thanks!
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D Voice
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| Posted: Tue Aug 31, 2010 3:47 pm Post subject: |
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Just to add on Chris' problem: I think it was actually the MXL 909 (not the 990), as well as on the MXL 3000 that he tried previously. The same mics do not seem to hum when used elsewhere, using various equipment; or using USB coverters at Chris'. Not sure about other manufacturer's mics at Chris'.
So it would seem to be either a grounding issue, or something in that particular chain.
(Besides obviously being better built), is there something about the design of the Neumanns (such as a different impedence) which would cancel out or eliminate the hum that would appear with other mics? |
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tokyofan
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Location: Tokyo, Japan
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| Posted: Tue Aug 31, 2010 11:19 pm Post subject: re: |
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I just tried the VO: 1A mic with the newly arrived Golden Age 73 pre and NO HUM! I'm guessing it might have something to do with the Chameleon Labs Power Adapter (Japan) that I ordered with it.
I'm going to post some sound samples on another thread. Please let me know what you think!
Thanks!
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D Voice
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| Posted: Wed Sep 01, 2010 5:15 am Post subject: |
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BTW Mike S:
That little 3 prong to 2 prong ground lift adapter depicted in your post:
if there is a wire coming out of it, could/should that be attached to the little screw on the face plate there? |
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Mike Sommer
A Hundred Dozen
Joined: 05 May 2008
Posts: 1222
Location: Boss Angeles
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| Posted: Wed Sep 01, 2010 10:09 am Post subject: |
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| D Voice wrote: | BTW Mike S:
That little 3 prong to 2 prong ground lift adapter depicted in your post:
if there is a wire coming out of it, could/should that be attached to the little screw on the face plate there? |
Yes, that's what it is there for.
Caveat, if you have a plastic outlet box this will not work. Then again if you have plastic outlet boxes in your home there should be Romex cable installed, with a ground lead. But sometimes people do some strange things in remodels and such.
A better option. have an electrocution come out and install a retro fit 3 prong outlet.
WARNING: BE CARFUL WHEN OPEING YOUR OUT LET BOXES. THERE ARE THINGS THAT CAN KILL YOU IN THERE> Be smart and shut down your power at the box when you open up your outlet boxes.
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Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong. |
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tokyofan
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Posts: 275
Location: Tokyo, Japan
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| Posted: Sat Sep 25, 2010 5:05 pm Post subject: re: |
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I found this post on Gearslutz:
A problem which occurs with some MXL 990s is that, due to the non-conductive paint used to finish the mic, the top half of the case does not electrically bond with the bottom half. The bottom half is grounded as it is bonded to XLR pin 1. The top half needs to be grounded because it shields the mic capsule. The fix is straightforward. If you are not comfortable doing it, have a friend skilled in electronics do it for you. You can test this problem by checking for continuity between XLR pin 1 and the wire mesh basket on top. If there is no continuity, there's your problem.
Unscrew the top half of the mic from the bottom half and remove the black trim ring. You will see how the two halves are supposed to make electrical contact when screwed back together. Using sandpaper or a small knife you need to remove some paint from where they are supposed to make contact. When the mic is reassembled (you can put the black trim ring back in) there should be electrical continuity between XLR pin 1 and the wire mesh basket.
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Mike Sommer
A Hundred Dozen
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Posts: 1222
Location: Boss Angeles
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| Posted: Sat Sep 25, 2010 6:44 pm Post subject: |
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I think that's what i suggested in the first post. It's a common problem with those mics.
Did it work?
_________________
The Blog:
http://voiceoveraudio.blogspot.com/
Acoustics are counter-intuitive. If one thing is certain about acoustics, it is that if anything seems obvious it is probably wrong. |
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