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Author Topic: Power line hum & digital console  (Read 16050 times)

David Sturzenbecher

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Re: Power line hum & digital console
« Reply #20 on: October 21, 2014, 09:08:29 AM »

Running the power to FOH from the stage, or the same power source as the amplifiers, etc.. is the correct method to use, as has been stated many times above. However, we often run into situations where a single piece of hardware hums and that hum seems to be impossible to get rid of. In those cases I use a HumX. The HumX cures the problem with that piece of hardware 99% of the time, and the cost is $50 or less. Keep in mind that the HumX is for use on a single piece of hardware.

http://www.ebtechaudio.com/humxvideo.html

$50 is a pretty high price for two diodes.  Is the hum-x Mike Sokol approved? Because it's not UL listed, and gets the thumbs down from Bill Whitlock on the Syn-Aud-Con forums.
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Steve M Smith

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Re: Power line hum & digital console
« Reply #21 on: October 21, 2014, 04:40:40 PM »

Are those two diodes back to back and in series with the ground connection?


Steve.
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Al Keltz

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Re: Power line hum & digital console
« Reply #22 on: October 21, 2014, 04:42:16 PM »

$50 is a pretty high price for two diodes.  Is the hum-x Mike Sokol approved? Because it's not UL listed, and gets the thumbs down from Bill Whitlock on the Syn-Aud-Con forums.

I managed to get a HUM-X open. The power LED is missing because it was destroyed in the autopsy. Yes, it's basically back to back diodes lifting the third prong.

- Al
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Bob Leonard

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Re: Power line hum & digital console
« Reply #23 on: October 21, 2014, 05:30:16 PM »

$50 is a pretty high price for two diodes.  Is the hum-x Mike Sokol approved? Because it's not UL listed, and gets the thumbs down from Bill Whitlock on the Syn-Aud-Con forums.

I doesn't really matter to me that the construction is simplistic, or that it's not UL approved, or if Bill likes the gadget or not. My deal is that it works as advertised, has gotten me out of more than one jam, and that makes it worth $50 to me. I could have made my own I suppose, but why bother.
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Bob Leonard

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Re: Power line hum & digital console
« Reply #24 on: October 21, 2014, 05:32:10 PM »

I managed to get a HUM-X open. The power LED is missing because it was destroyed in the autopsy. Yes, it's basically back to back diodes lifting the third prong.

- Al

How much will the Whirlwind version cost?
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Scott Holtzman

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Re: Power line hum & digital console
« Reply #25 on: October 21, 2014, 06:39:43 PM »

So it's a 1/2 wave rectifier in series with ground? 
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Steve M Smith

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Re: Power line hum & digital console
« Reply #26 on: October 22, 2014, 02:58:47 AM »

So it's a 1/2 wave rectifier in series with ground?

More like an ac 0.7v voltage drop in series with ground.

I think the idea is that the diodes introduce enough resistance to stop earth loops but can still carry enough fault current to trip the supply in case of a fault.


Steve.
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Tim McCulloch

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Re: Power line hum & digital console
« Reply #27 on: October 22, 2014, 03:00:04 AM »

I had another reply that either never made it or I close my browser before sending...

Part of the reason new devices, whether digital or analog, have far fewer humm/buzz issues is due to better design of the signal grounding withing those devices.  The "Pin 1 problem" isn't a thing of the past, but it's much better than as recently as 10-12 years ago.

As was pointed out in another reply, the shield of an RJ45 connection is connected to chassis ground, so it's possible to have a ground loop; what it might sound like is for others to suggest.
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Tom Bourke

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Re: Power line hum & digital console
« Reply #28 on: October 22, 2014, 04:13:19 AM »

As was pointed out in another reply, the shield of an RJ45 connection is connected to chassis ground, so it's possible to have a ground loop; what it might sound like is for others to suggest.
If you want to see what a modern pin 1 problem looks like see here http://forums.prosoundweb.com/index.php/topic,143428.0.html

Analog pin 1 is a known problem that has been solved and is cheap enough for even the lowest manufacturer to deal with.  That is assuming they read the application notes for what ever part they are using.
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Steve M Smith

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Re: Power line hum & digital console
« Reply #29 on: October 22, 2014, 05:14:25 AM »

The problem I see with the HumX is that when you have two pieces of equipment connected with a signal lead tying their grounds together, if there is a fault in the equipment with a HumX connected, it's fault current will prefer to run through the connecting lead shield to the ground connection on the non HumX piece of equipment rather than through the two diodes now connected in series with its own earth connection.

It's only slightly better than the old and dubious practice of cutting the ground connection in the mains plug to reduce hum.


Steve.
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Re: Power line hum & digital console
« Reply #29 on: October 22, 2014, 05:14:25 AM »


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