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Buzz from lexicon lx-7 power amp

Hi i have a problem wit my lexicon power amp, a buzzing/hum coming from all the channels. Its only very faint when its just the power amp on and nothing is connected to it but the speakers. buzz gets louder when i connect the pre amp to the RCA inputs on the power amp. it get even louder when i switch the plasma on. which is connected to the pre amp with a component lead, if i disconnect the component the buzz is reduced. Is there a fualt with the power amp as i'v treid loads of ways to get rid of the buzz.

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Might be caused by any of the Large Capacitors in the power supply section of the amp.

Posted on Feb 16, 2009

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How do I eliminate buzz?


Things to check:
1. With your multi meter, measure from left ground to right ground. What do you get? Measure from each input ground to chassis. What do you get there.

2. Get or make a pair of shorting plugs. Plug those into the inputs. Power on. Hum there or gone?

3. Turn the pre-amp on. Connect. Level of hum change with preamp on?

4 additional information. How efficient are your speakers? This is a big amp, high-efficiency speakers may show some noise, while low-efficiency speakers won't.

A trip back to the shop may be indicated, too.

Nov 23, 2015 | Adcom GFA-5500 2-Channel Amplifier

1 Answer

I have kenwood amp m-a100 which has loud buzz / hum on all channels and distorts radio very badly can you help ?


The loud hum will be probably caused by the Large Electrolytic Capacitors in the Power Supply section. All of them will need to be replaced to be on the safe side. The buzz noise is caused by the fact they are letting in the 50/60hz mains. Hopefully that should clear everything up.

Sep 09, 2014 | Amplifiers & Preamps

1 Answer

I have a huge Buzzzz with my Peavey Model 115BW Session 500, no matter what I do, buzz buzz buzz, I have taken it apart to get to the main caps, found neg 50vdc on one main and found neg15vdc on the other,...


Hum or buzz is often caused by the mains filter capacitor letting the 50hz mains hum into the system. Regardless of voltages you just need to try new capacitors. If that doesn't cure it, the problem is elsewhere. If it's a stereo amp and the buzz is on both channels then it's something common to both channels.

Sep 14, 2013 | Amplifiers & Preamps

1 Answer

One bad channel


The thing with stereo amps is that they are actually two mono channels put together, so if one side goes you have the other side to tell you what the other side should be doing. So you can compare the good channel with the bad. For example taking voltage readings. Also you can buzz test it. Generally you can touch with an insulated tool parts of the amp to produce a buzz. So if it buzzers in the good channel it should buzz in the bad. When it doesn't you have found the bad part!

May 18, 2013 | NAD C160 Amplifier

1 Answer

Bugera 333xl every few seconds there is a loud buzzing. from


It looks as though you have ripple noise that amplifies into the output. First of all check if the mains voltage is going down to produce the low voltage hum. If not you will have to check the DC filter capacitors , couple in parallel to confirm the capacitor. IF the buzz is still coming through then you will have to isolate the preamp and wait it the fault is coming in. If not connect the preamp output to another amp to hear the same buzz to confirm the preamp to be faulty. If so you will have to trace by a voltage check when the buzz occurs to confirm if the preamp IC or the selector Ic is faulty. Some logic IC's can also produce this noise on static switching. If teh noise is appearing on both the channels, then I would still bet on the power section. So check once again on the rectifier/ regulators and capacitors. Hope this advice helps. Good day

May 16, 2010 | Amplifiers & Preamps

2 Answers

Crate gtx 65 guitar amp mains hum


I had the same problem on my VTX65. I noticed it would oscillate with different effects so I removed the effects module. Problem solved. Now it's dead quiet. I use a Digitech RP500 so removing the effects module was a non issue.

May 19, 2009 | Lexicon LX-7 7-Channel Amplifier

1 Answer

Carver PM900 power amp with hum/buzz


1-shut down all flourecent lamp and check.
2-check for your cables in a good condition and no touching of wires to the body of amp.
3-connect(ground loop isolator)code number(270-054)from radio shack near you and connect it between your audio device(like cd player and amp)

Apr 15, 2009 | Amplifiers & Preamps

1 Answer

Lexicon Lx-7 buzz sound


Hi chupetin2

If the problem is present with ONLY the speakers connected, that is no other powered devices like subs, or input/output cables, it will be a power supply problem inside the amp. If you have electronic fault finding skills, there will probably be a capacitor in a regulated rail that has failed.
If you do have a sub connected, be sure it is powered from the same mains source as the amp, or at least a GPO that is on the same phase. Different phases will induce mains hum, as will multiple earths. Try also temporarily moving the amp(whilst monitoring the hum) from where it is sitting and see if the hum is being induced into the amp by any other devices

Happy to talk to you more about this. Just ask:)

regards
robotek

Aug 18, 2008 | Lexicon LX-7 7-Channel Amplifier

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