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Author Topic: Gear next to other gear in a rack inducing noise.  (Read 2297 times)

Jim Williams

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Re: Gear next to other gear in a rack inducing noise.
« Reply #15 on: October 08, 2010, 10:32:07 am »

Any DSP box with analog already inside is a "you are what you is" Frank Zappa scenerio. Do avoid pure analog processors next to DSP switching power gear. That includes line level EQ's, compressors, mic preamps, etc. I place all my DSP reverbs in their own rack, the analog gear is in it's own rack. I avoid placing anything with a digital clock near any analog gear.

I do use metal racks as they have the best screening and mechanical mounts. I do use isolation washers on each rack screw. Electrical isolation is maintained this way. To check I use a meter to each chassis to ensure isolation.

The reason for that is the "doesn't play well with others" problems you eventually come across. Some gear connects their audio grounds to chassis, some float it, some use a RC network. Without knowing how to read schematics I don't know how anyone can suss all that out and get each piece grounded correctly. That's probably why large well funded installs pay for professional help. The end result should be zero hum anywhere and very low hiss levels.
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Jim Williams
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Bill Mueller

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Re: Gear next to other gear in a rack inducing noise.
« Reply #16 on: October 08, 2010, 11:02:02 am »

Jim Williams wrote on Fri, 08 October 2010 10:32

Any DSP box with analog already inside is a "you are what you is" Frank Zappa scenerio. Do avoid pure analog processors next to DSP switching power gear. That includes line level EQ's, compressors, mic preamps, etc. I place all my DSP reverbs in their own rack, the analog gear is in it's own rack. I avoid placing anything with a digital clock near any analog gear.

I do use metal racks as they have the best screening and mechanical mounts. I do use isolation washers on each rack screw. Electrical isolation is maintained this way. To check I use a meter to each chassis to ensure isolation.

The reason for that is the "doesn't play well with others" problems you eventually come across. Some gear connects their audio grounds to chassis, some float it, some use a RC network. Without knowing how to read schematics I don't know how anyone can suss all that out and get each piece grounded correctly. That's probably why large well funded installs pay for professional help. The end result should be zero hum anywhere and very low hiss levels.

Jim,

Great stuff. Over the years, I have seen it both ways.

1. Ground all chassis.
2. Lift all chassis and rely on the internal grounding scheme of each unit.

My issue with lifting all chassis is unless all the units are transformer isolated, they are going to get chassis connected through their inputs and outputs anyway, defeating the lift at the rail.

What do you think about this?

Bill
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Barkley McKay

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Re: Gear next to other gear in a rack inducing noise.
« Reply #17 on: October 08, 2010, 11:22:36 am »

I learned a lot the hard way by trial and error, but I am learning a lot here again.

Great stuff.

This should be a sticky!

cheers

barks
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Jim Williams

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Re: Gear next to other gear in a rack inducing noise.
« Reply #18 on: October 10, 2010, 10:54:17 am »

Bill Mueller wrote on Fri, 08 October 2010 08:02

Jim Williams wrote on Fri, 08 October 2010 10:32

Any DSP box with analog already inside is a "you are what you is" Frank Zappa scenerio. Do avoid pure analog processors next to DSP switching power gear. That includes line level EQ's, compressors, mic preamps, etc. I place all my DSP reverbs in their own rack, the analog gear is in it's own rack. I avoid placing anything with a digital clock near any analog gear.

I do use metal racks as they have the best screening and mechanical mounts. I do use isolation washers on each rack screw. Electrical isolation is maintained this way. To check I use a meter to each chassis to ensure isolation.

The reason for that is the "doesn't play well with others" problems you eventually come across. Some gear connects their audio grounds to chassis, some float it, some use a RC network. Without knowing how to read schematics I don't know how anyone can suss all that out and get each piece grounded correctly. That's probably why large well funded installs pay for professional help. The end result should be zero hum anywhere and very low hiss levels.

Jim,

Great stuff. Over the years, I have seen it both ways.

1. Ground all chassis.
2. Lift all chassis and rely on the internal grounding scheme of each unit.

My issue with lifting all chassis is unless all the units are transformer isolated, they are going to get chassis connected through their inputs and outputs anyway, defeating the lift at the rail.

What do you think about this?

Bill


That's the rub, maybe they do, maybe they don't. As I mentioned, some float audio/chassis grounds, some isolate it with a small capacitor, some use an RC network, some tie it to chassis ground. Right there you've got four scenarios to choose from.

The idea is to keep ground return currents from having multiple return paths = loops. Each piece must be analyzed separately from the others. You may end up using different schemes for different pieces, there are no set rules when there is so much variance in design. If I had a "one size fit's all" solution I would offer it.
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Jim Williams
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