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Amplifier hum
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Joined: Aug 2012
Posts: 8
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OP
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Joined: Aug 2012
Posts: 8 |
I have just recently purchased a crown XLS1500 amplifier to be used with my Onkyo 875 receiver to power my front M80s. I didn't realize that the amp could only work with a 120 volt power supply. I only have 240 volt where I live. I then decided to try a cheap step down transformer to step 240v down to 120v. Suprising that this crown XLS1500 amp only draws max 250 watts yet claims to put out over 500 watts/channel into 4 ohms. Anyway that is a separate story. With everything connected up I am getting a low frequency hum from the fronts. When I disconnect the rca input to the crown the hum disappears. It is only present when the onkyo receiver is on and the pre-amp out is connected to the crown amp. Is there any way I can eliminate this hum or reduce it. Should I use the XLR inputs on the Crown. To do this I would need to get an RCA to XLR adaptor. Is it possible this hum is caused by the step down transformer? I doubt it since the hum is not always present. Any ideas?
Last edited by grantlyt1; 08/25/12 10:57 PM.
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Re: Amplifier hum
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Joined: Sep 2004
Posts: 11,458
shareholder in the making
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shareholder in the making
Joined: Sep 2004
Posts: 11,458 |
Is everything plugged into one outlet? It sounds like a ground hum which often pops up when interconnected devices are plugged into different outlets.
Try a cheater plug (no ground prong) to see if that makes the hum go away.
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::
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Re: Amplifier hum
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Joined: Aug 2012
Posts: 8
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OP
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Joined: Aug 2012
Posts: 8 |
Yes everything is plugged into the one outlet. I even disconnected all devices and left only the receiver and amplifier connected but still the same problem. Is the use of this cheater plug dangerous?
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Re: Amplifier hum
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Joined: Jan 2004
Posts: 13,840 Likes: 13
shareholder in the making
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shareholder in the making
Joined: Jan 2004
Posts: 13,840 Likes: 13 |
Are all your outlets on the same circuit to the breaker? Might be a ground loop hum. If you have a sub, what happens if you unplug the interconnect?
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Re: Amplifier hum
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Joined: Sep 2004
Posts: 11,458
shareholder in the making
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shareholder in the making
Joined: Sep 2004
Posts: 11,458 |
No, though it's better used as a diagnostic tool than a permanent solution.
Do you have a coax cable (TV, Cable) going into a device that's plugged into the receiver? If so, try disconnecting the coax cable.
::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::
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Re: Amplifier hum
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Joined: Aug 2012
Posts: 8
regular
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OP
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Joined: Aug 2012
Posts: 8 |
Yes the outlets are on the same circuit breaker. Disconnecting the pre-amp out to the sub has no effect on the hum.
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Re: Amplifier hum
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Joined: Feb 2004
Posts: 1,863
connoisseur
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connoisseur
Joined: Feb 2004
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Should I use the XLR inputs on the Crown. To do this I would need to get an RCA to XLR adaptor. Is it possible this hum is caused by the step down transformer? I doubt it since the hum is not always present. Any ideas? To get the true benefit of XLR connectors you're receiver/processor would have to have XLR outs... XLR's are a 3 wire system, RCA is a 2 wire system... To get rid of the hum, you need a true 3 wire system. I had the same problem, i think it's the wiring in my house.. I am using all XLR connectors. However, my processor has XLR outputs.... By using a step down transformer, are isolating that outlet. My money is on a ground loop problem. My house also have a ground loop... So, i have to deal with multiple electrical issues.....
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Re: Amplifier hum
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Joined: Aug 2012
Posts: 8
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OP
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Joined: Aug 2012
Posts: 8 |
I disconnected all inputs to the receiver but no difference however I just disconnected the hdmi out from the receiver and the hum is significantly reduced. Still annoying but much better. But I need to use this HDMI output.
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Re: Amplifier hum
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Joined: Feb 2004
Posts: 1,863
connoisseur
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connoisseur
Joined: Feb 2004
Posts: 1,863 |
you may not have a good earth ground.... that is one other possibility.
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Re: Amplifier hum
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Joined: May 2003
Posts: 18,044
shareholder in the making
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shareholder in the making
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Where do you live? I would wager that this has something to do with the step down transformer.
Guys, if he's got 240V, I doubt they even have cheater plugs...
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