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PostPosted: Fri Oct 06, 2017 8:01 am 
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Joined: Sat Aug 22, 2009 6:38 pm
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Location: toronto, ON, CA
Hi everyone,

I recently got a new tube power amp and I recently realized that there is some hum/static coming from the speakers. So, I disconnected everything from the amp and the hum/static is now gone. If a connect one end of an rca to the amp and nothing on the other end there is no hum/static. However, when I connect "any" source to the amp, even if the source is off, the hum/static is back. The only source that doesn't cause the hum/static is a cd player with a 2 prong power cable. So I figured that there is a ground issue, not necessarily with my sources as my other amps dont have this issue. So I connected the sources to the amp again using a 3 to 2 prong adapter and the um/static is gone. So I think the problem may be the new amp since my other amps dont have this issue and all my sources cannot be defective, at least its very unlikely as I dont have this issue with my other amps. Any ideas?

I greatly appreciate your help.

Ed


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PostPosted: Fri Oct 06, 2017 8:30 am 
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Location: Etobicoke, ON, CA
First, are all your components plugged into the same conditioner or power strip so they share a common ground or are you using more than one wall outlet.

Also, is the noise you hear static or hum or both. Ground loops will produce a 60 Hz. hum but no static.
Static may be caused by an incorrect polarity of AC power. Perhaps one of your outlets or power cords is incorrectly wired.

If you are confident that all your wiring is correct with respect to polarity then I would go with lifting the ground on your new amplifier although you should not have to. These kinds of noise issues are difficult to diagnose over the internet but static usually suggests something is insufficiently grounded and poses an electrical potential. I see you are in Toronto so (PM) me if you wish to have this looked at in person.

Cheers,

Jon


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PostPosted: Fri Oct 06, 2017 8:44 am 
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The only use for a cheater plug is to identify the offending component. Cheater plugs used to lift the ground should never be used as a solution as they present safety hazard. I know that with my tube amplifier produces 1200 volts to the plates and that voltage is lethal.

If your amp draws less than 6A and/or 720 watts from the wall, try using an Ebtech HumX Ground Loop eliminator.


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PostPosted: Fri Oct 06, 2017 9:03 am 
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Location: toronto, ON, CA
Thank you for your replies guys, I really appreciate it.

To answer some of your questions, all components are connected to the same power strip. I also connected them directly to the wall outlet and to different wall outlets but the problem remained. As for hum/static Id say its probably hum as its continuous, but I could be wrong.

I will try different power cords and see if that rules out polarity issues. Thanks for suggesting it Jon. As for the adapter, I used it on the source as opposed to the amp because I read that its dangerous to use it on tube amps as brf mentioned (thanks for mentioning it, safety first). I get the feeling that its something inside the amp. Its still under warranty so Ill probably have to send it back, although its a pain since its super heavy. What a way to ruin the fun of getting a new amp.

Ed


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PostPosted: Fri Oct 06, 2017 9:53 am 
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Location: toronto, ON, CA
I found this post on the net. It seems to be related to my issue. Ill give it a try.

https://forum.audiogon.com/discussions/ ... c-polarity


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PostPosted: Fri Oct 06, 2017 10:03 am 
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What tube amp to you have?

Also, using a cheater plug on any equipment presents a safety hazard as 120v can kill you


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PostPosted: Fri Oct 06, 2017 10:08 am 
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Mcintosh 275. I am using the 3 to 2 prong adapter on the preamp/dac to avoid issues, not on the amp. Although Im thinking of not using the adapter at all just to avoid any damage to the preamp/dac.


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PostPosted: Fri Oct 06, 2017 10:24 am 
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edgarin8 wrote:
Mcintosh 275. I am using the 3 to 2 prong adapter on the preamp/dac to avoid issues, not on the amp. Although Im thinking of not using the adapter at all just to avoid any damage to the preamp/dac.


You amp draws 3.6 amps, therefore, go out and purchase a Hum X ground loop eliminator ($109) from the AV Shop https://www.avshop.ca/sound-amp-pa-audio/audio-accessories/hum-eliminators/ebtech-humx-power-line-60hz-ground-hum-buzz-filter and plug in your Mac 275 and you will listening to hum free music before dinner. They have a retail outlet in Markham and you can return it if it does not work.


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PostPosted: Fri Oct 06, 2017 11:01 am 
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What a coincidence, I just watched a youtube video were the same product is recommended. So its normal that the amp is producing that hum? I just figured there should be no hum at all, the amp being so expensive and all.

Thanks for the info brf, I really appreciate it.


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PostPosted: Fri Oct 06, 2017 11:37 am 
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You said yourself that the amplifier does not hum until it is fed a lead from a component. Therefore I suggest there is nothing wrong with the amp. One or more of your components is ungrounded or has a 'floating ground' and is feeding your amp 60Hz at a very low voltage. That's all it takes to create a constant hum.

I am assuming this is an integrated amplifier. I suggest you try lifting the ground on each source component, one at a time and listen for a change in hum level. Even a very tiny voltage between two ground locations can cause a significant hum. Are you certain that your wall outlets are completely grounded. Many older homes have their wiring upgraded with new outlets which give the appearance of modern wiring but in reality the conductors in the wall are still hot and neutral only with nothing connected to the ground contact.

A voltmeter will tell you all you need to know in a heart beat.

J.


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PostPosted: Sun Oct 08, 2017 6:19 am 
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Yeah the funny thing is that all sources create a hum on the amp when connected to it, except a cd player with a two prong power cable, the rest of the sources have three prong power cables. This leads me to believe that the amp is at fault. I lifted the ground an the dac I just got and all is ok. I will get a multimeter to check the wall outlets. Although the wiring should be relatively modern as the building is about 20 years old. By the way, the Amp is a power amp.

As for being ungrounded, you mean the sources may not be properly grounded inside? What do you mean by floating ground? If the sources dont create a hum on an integrated solid state amp, does that confirm that the sources are not the problem?

Thanks J


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PostPosted: Sun Oct 08, 2017 6:38 am 
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Location: Winnipeg, MB, CA
The exact same issue occurred for me when I brought home new tube mono blocks.
To rectify it I now plug the mono blocks into its own conditioner strip which then goes to the dedicated line outlet. Remaining grounded components are now plugged into a PS Audio juice box which is also plugged into the dedicated outlet. This solved the issue for me


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PostPosted: Sun Oct 08, 2017 7:02 am 
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Location: Stratford, ON, CA
Hi,

Note to the OP. Prosoundman has the advice you need. Grounding issues are pernicious and often very hard to pin down. Call a friend. Take the amp in question to their place and hook it up. If it hums then it is the amp and the fault is likely in the amp's RCA input strip wiring. If it doesn't hum then you have a floating ground issue in your home wiring or in the power bar. In a very sensitive amplifier it only takes a smidgeon of ungrounded AC to generate a noticeable background hum. I feel for you.

Cheers,
David Neice

_________________
Chinese Proverb: 'Man who waits for roast duck to fly into mouth, waits very, very long time'.


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PostPosted: Sun Oct 08, 2017 7:07 am 
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The fact that your other amp does not experience a ground loop does not make your new amp defective. Each piece of equipment interacts differently with one another. Your new amp has a different ground potential than your former amp which is causing a ground loop. You can Star ground all of your components together to achieve a common ground potential, thus eliminating the ground hum.

The fact that a two prong ac cord with a lifted ground pin connected to your amp solves your problem (but unsafe to use as a long term solution), tells me that my previous recommendation for a HumX will eliminate your ground loop problem.


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PostPosted: Sun Oct 08, 2017 12:03 pm 
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Location: toronto, ON, CA
Further testing just left me even more perplexed. I was able to borrow a solid state integrated amp and this are the results I got:

Dac as preamp/dac - RCA - new tube power amp = hum
Dac as preamp/dac - RCA - ss integrated (power section) = hum
Dac as dac only - RCA - ss integrated (preamp and power section) = No hum :shock:
Integrated (preamp section) - RCA - new power amp = hum

Using a power cord without the ground prong got rid of the hum if used in either the source or either of the the amps.

So I dont know what to gather from the above. The real question is, should I just buy the humx and forget about it or get the dealer of the amp take a look at the amp to see if there is anything wrong with it. I just dont want to postpone dealing with this if it really is an issue with the components, but thats the thing, its hard to tell :oops:

Anyhow thank you everyone for your help.


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