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Author Topic: Gear next to other gear in a rack inducing noise.  (Read 2301 times)

eightyeightkeys

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Gear next to other gear in a rack inducing noise.
« on: October 03, 2010, 07:24:02 pm »

Continuing the "Unbalanced Noise" thread, I also became hyper aware of other noise in the studio. As I got rid of computer/printer high freq "whines" and Powercore computer hash, I started to become aware of other noise....damn it.

I noticed that my external preamp was emitting a low-level 60 cycle hum...very low level, but, why the hell should there be any at all ?

So, I pulled it out of the rack to make sure I isolated the preamp from the rack rails and, yes, I did....but, as I pulled it, I noticed that the hum went away !
So, wtf ?....I lifted the ground....nothing no help there.

I decided to move it away from my Mackie mixer that I use for headphone cues and voila ! The 60 cycle hum is gone.
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Dave T.
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compasspnt

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Re: Gear next to other gear in a rack inducing noise.
« Reply #1 on: October 03, 2010, 10:00:14 pm »

Is there a transformer in that preamp?  EQ included in it as well?
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Bill Mueller

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Re: Gear next to other gear in a rack inducing noise.
« Reply #2 on: October 03, 2010, 10:46:57 pm »

eightyeightkeys wrote on Sun, 03 October 2010 19:24

Continuing the "Unbalanced Noise" thread, I also became hyper aware of other noise in the studio. As I got rid of computer/printer high freq "whines" and Powercore computer hash, I started to become aware of other noise....damn it.

I noticed that my external preamp was emitting a low-level 60 cycle hum...very low level, but, why the hell should there be any at all ?

So, I pulled it out of the rack to make sure I isolated the preamp from the rack rails and, yes, I did....but, as I pulled it, I noticed that the hum went away !
So, wtf ?....I lifted the ground....nothing no help there.

I decided to move it away from my Mackie mixer that I use for headphone cues and voila ! The 60 cycle hum is gone.


Dave,

Is that a metal rack with a ground strap?

Bill
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CWHumphrey

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Re: Gear next to other gear in a rack inducing noise.
« Reply #3 on: October 03, 2010, 10:58:32 pm »

A Transformer is an inductor after all.

Sixty Hertz straight from the Mackie PSU.

Cheers,

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eightyeightkeys

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Re: Gear next to other gear in a rack inducing noise.
« Reply #4 on: October 04, 2010, 10:17:41 am »

Quote:

Is there a transformer in that preamp? EQ included in it as well? Dave,


It's a Studio Technologies Mic-PreEminence mic pre...no EQ....

Quote:

Is that a metal rack with a ground strap?

Bill


It's a wooden box with metal rack rails and no grounding strap.

Quote:

A Transformer is an inductor after all.

Sixty Hertz straight from the Mackie PSU.

Cheers


The old 1604VLZ's had no talkback mic, so, I used an SM57 on top of the box for a talk back. It also picked up gobs of hum from the Mackie before I moved it.

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Dave T.
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Extreme Mixing

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Re: Gear next to other gear in a rack inducing noise.
« Reply #5 on: October 04, 2010, 07:43:52 pm »

I had the same thing from a MOTU 2408.  It caused my Neves to hum.  I moved it and the problem is gone.

I sure miss my StudioTechnologies Mic PreEminence.  That was a great preamp.

Steve

eightyeightkeys

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Re: Gear next to other gear in a rack inducing noise.
« Reply #6 on: October 04, 2010, 08:32:58 pm »

Yeah, I really like the Mic-PreEminence pre. When I was in the market for a new pre, I did a shoot out with several others in it's price range, even single channel, and this one really stood out.
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Dave T.
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Ryan Slowey

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Re: Gear next to other gear in a rack inducing noise.
« Reply #7 on: October 05, 2010, 09:59:49 am »

My TAB V78M had the same problem when it was too close to my power conditioner. Took some headscratching to figure it out, but once I moved it a couple rack spaces away, it was fine.

It's happened with other gear as well, when bringing it to another studio in my portable rack. It's even happened sort of randomly, where it'll be noise free for a few hours, then suddenly a 60 cycle hum appears. I thought that was a little weird.
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Ryan Slowey
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MagnetoSound

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Re: Gear next to other gear in a rack inducing noise.
« Reply #8 on: October 05, 2010, 10:08:38 am »


From your first post, it seems pretty clear that - either - the proximity of the power transformer in the Mackie is inducing hum in the preamp's mic transformer - or - there was a ground loop set up by two (or more) pieces of gear in the rack being in contact with the rack rails ...

Some further experimenting should indicate exactly which it is (possibly both, even) but I'm leaning towards the former.

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Jim Williams

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Re: Gear next to other gear in a rack inducing noise.
« Reply #9 on: October 05, 2010, 11:10:47 am »

"Does not play well with others" is the theme here. Throwing together audio gear, especially in racks haphazardly will lead to these problems.

A quality install will test each piece with a noise vs frequency sweep using an Audio Precision or similar analyzer. The idea is to not make anything worse.

Easy decisions include mounting gear with power transformers all on the same side. Avoid using dbx next to gear with right side power transformers. They are on the left side in dbx stuff.

Avoid mounting dsp boxes with switching power supplies next to sensitive analog gear like mic preamps. An Eventide H-3000 mounted in the same rack as a dbx compressor will cause the dbx THD to rise well above 1/2% THD even if they are separated by several spaces.

Remember: When gear makers test their stuff it's stand alone. They never test it with other gear nearby nor when mounted in racks with other pieces. You are the test engineer when you install equipment. It takes more thought than screwing in 4 bolts.
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Bill Mueller

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Re: Gear next to other gear in a rack inducing noise.
« Reply #10 on: October 05, 2010, 12:12:28 pm »

Jim Williams wrote on Tue, 05 October 2010 11:10

"Does not play well with others" is the theme here. Throwing together audio gear, especially in racks haphazardly will lead to these problems.

A quality install will test each piece with a noise vs frequency sweep using an Audio Precision or similar analyzer. The idea is to not make anything worse.

Easy decisions include mounting gear with power transformers all on the same side. Avoid using dbx next to gear with right side power transformers. They are on the left side in dbx stuff.

Avoid mounting dsp boxes with switching power supplies next to sensitive analog gear like mic preamps. An Eventide H-3000 mounted in the same rack as a dbx compressor will cause the dbx THD to rise well above 1/2% THD even if they are separated by several spaces.

Remember: When gear makers test their stuff it's stand alone. They never test it with other gear nearby nor when mounted in racks with other pieces. You are the test engineer when you install equipment. It takes more thought than screwing in 4 bolts.

Jim,

Good stuff here.

Dan,

His racks are wooden boxes with no ground on the the rails, so it would be easy to create loops. A ground strap on a rail would be in order.

Bill
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"Don't take it personally. But this shit is a science." J.J.Blair

“The Internet is only a means of communication,” he wrote. “It is not an amorphous extraterrestrial body with an entitlement to norms that run counter to the fundamental principles of human rights. There is nothing in the criminal or civil law which legalizes that which is otherwise illegal simply because the transaction takes place over the Internet.” Irish judge, Peter Charleton

drknob

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Re: Gear next to other gear in a rack inducing noise.
« Reply #11 on: October 05, 2010, 12:19:41 pm »

And if you really want to go for it, use wooden 'rack rail' and drywall screws so that no chassis are connected through a metal rail. You shouldn't have to jump through these hoops, but.....
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Harold Kilianski
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eightyeightkeys

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Re: Gear next to other gear in a rack inducing noise.
« Reply #12 on: October 05, 2010, 01:12:35 pm »

[quote title=Bill Mueller wrote on Tue, 05 October 2010 12:12]
Jim Williams wrote on Tue, 05 October 2010 11:10

"Does not play well with others" is the theme here. Throwing together audio gear, especially in racks haphazardly will lead to these problems.....

Good stuff here.

Dan,

His racks are wooden boxes with no ground on the the rails, so it would be easy to create loops. A ground strap on a rail would be in order.

Bill


I agree Bill, really good stuff here and thanks. This forum really is the best.

How do you do a proper grounding strap on rack rails across multiple racks ?
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Dave T.
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Bill Mueller

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Re: Gear next to other gear in a rack inducing noise.
« Reply #13 on: October 05, 2010, 01:44:35 pm »

[quote title=eightyeightkeys wrote on Tue, 05 October 2010 13:12]
Bill Mueller wrote on Tue, 05 October 2010 12:12

Jim Williams wrote on Tue, 05 October 2010 11:10

"Does not play well with others" is the theme here. Throwing together audio gear, especially in racks haphazardly will lead to these problems.....

Good stuff here.

Dan,

His racks are wooden boxes with no ground on the the rails, so it would be easy to create loops. A ground strap on a rail would be in order.

Bill


I agree Bill, really good stuff here and thanks. This forum really is the best.

How do you do a proper grounding strap on rack rails across multiple racks ?


Dave,

Equal lengths of #14 wire screwed into each rack rail, grouped in a service box and then to the ground pin of an AC plug, plugged into the power source for the racks. You will have coils laying in the bottom of some of the racks but that is fine.

Bill
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"Don't take it personally. But this shit is a science." J.J.Blair

“The Internet is only a means of communication,” he wrote. “It is not an amorphous extraterrestrial body with an entitlement to norms that run counter to the fundamental principles of human rights. There is nothing in the criminal or civil law which legalizes that which is otherwise illegal simply because the transaction takes place over the Internet.” Irish judge, Peter Charleton

eightyeightkeys

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Re: Gear next to other gear in a rack inducing noise.
« Reply #14 on: October 07, 2010, 12:57:25 pm »

Jim Williams wrote on Tue, 05 October 2010 11:10

"Does not play well with others" is the theme here. Throwing together audio gear, especially in racks haphazardly will lead to these problems......
....Avoid mounting dsp boxes with switching power supplies next to sensitive analog gear like mic preamps. An Eventide H-3000 mounted in the same rack as a dbx compressor will cause the dbx THD to rise well above 1/2% THD even if they are separated by several spaces.....It takes more thought than screwing in 4 bolts.


Jim, continuing with this topic, I've run into other "issues."

1) I've got my studio about as "clean" as I've ever had, but, just to cover all the bases, my TC Powercore Firewire rack mount, is bolted right next to my RME Multiface 2 which does have 8 analog ins and outs. Above, you said,

"Avoid mounting dsp boxes with switching power supplies next to sensitive analog gear..."

Are these two units so close together a potential noise problem ?

2) Monster Power HTS 3600 MkII :
The people of at Monster Power Canada are unbelievably good to me. I had an HTS 3600MKII start to beep indicating a failed unit, they promptly sent me a new one. Free !

I decided to try their UPS unit the HTUPS 3600 and, as soon as I plugged my computer and monitor into this unit, the bzz, bzz on changing screens returned ! I'm not interested in dicking with this unit, or any other, so back it goes. I've determined that the cleanest power is coming straight from the wall.  
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Dave T.
D&D Music
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