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Krell sav250a power amp

Humming sound in my speakers when connect to above. all cables ok. Perhaps it's the ground loop. I use biamp to drive my speakers. Other power amp classe ca300. Pre-amp arc 2b. Any solution? Thanks

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  • tongjenglaw Jul 05, 2008

    Hi,
    No hum when the krell is unplugged. Only when it is switch on and connected to the speakers. The hum comes from the speakers.
    Thanks


  • Graeme Ross
    Graeme Ross May 11, 2010

    Hi tongjenglaw

    Do you still have the hum with the inputs to the Krell unplugged.

    regards
    robotek


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Hey tong

This confirms you have an earth loop problem then. Has it just started, or has it been this way from when you first set up the gear?


Posted on Jul 05, 2008

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After a power outage I have a loud hum.


Hi, The Ground Rules Of all the annoyances that can afflict any audio/video home theater or even a simple stereo installation, the notorious "ground loop" may well be the most difficult and persistent one to track down and eliminate. A "ground loop" is caused by the difference in electrical potential at different grounding points in an audio/video system. (All the grounds in an A/V system should ideally be at "0" potential.) A ground loop typically adds a loud low-frequency hum or buzz as soon as you plug in any of various audio or video components, including subwoofers, cable-TV outboard boxes, satellite-TV feeds, TV displays, amplifiers, A/V receivers or turntables. The buzz/hum is a byproduct of the multiple power supply cables and a ground voltage differential within your system and its network of interconnecting cables.

Here are some methods to help you get rid of ground loops. Try these first and don't waste money on a power "conditioner" which, in most cases, won't help. (There is no need to "condition" the AC power for your system. Your receiver or amplifier already has a power supply with its own filters and transformers. No further filtering is normally required.)

If you get your system up and running and hear an audible buzz or hum, the first culprit to look at is either the powered subwoofer or your cable-TV or satellite-box feed at the entry point to your system.

First, the subwoofer: unplug the coaxial cable that connects to your powered subwoofer to see if the ground-loop hum disappears. If it does, it's likely coming in through your cable/satellite TV feed.

Reconnect your subwoofer's coaxial cable from the subwoofer input to your receiver's subwoofer output and disconnect the cable-TV feed (or satellite feed) from your outboard set-top cable box or satellite tuner. Be sure and disconnect the cable before any splitters. Now see if the hum/buzz from your subwoofer stops.

If that eliminates the hum, you can install one of these inexpensive in-line ground isolators from Parts Express or Bass Home. Note that these transformer-based ground isolators will work fine with analog cable-TV feeds, but depending on their design they may interfere with or block reception of HDTV signals via a digital cable or satellite dish feed.

Install the ground isolator between the cable-TV feed and the input of your outboard cable-TV box or satellite tuner (or the TV display's antenna or cable input if you have a set with a built-in TV tuner or a cable-card ready set). In many cases, the ground isolator will "break" the loop and remove the annoying hum or buzz by isolating the TV-cable ground.

If a hum remains with the TV cable completely disconnected from your system, or you don't want to risk degrading reception of HD signals from a cable or satellite system, then you may have to add a ground isolator like this Radio Shack Model 270-054 between the line-level coaxial subwoofer cable from your A/V receiver and the line-level input jack on your powered subwoofer.

In all cases, if your subwoofer has a ground-lift screw like some of Axiom's subwoofers, try first removing the screw (or replacing it) to see if it increases or eliminates the hum. It may or may not make a difference.

If you do not have easy access to the aforementioned ground isolators, here are a few more tips:

Try plugging the subwoofer into a different AC outlet in the room, one that isn't supplying power to your components (A/V receiver, TV, cable box, etc.). That might fix it.

Try reversing the AC plug for your A/V receiver or the powered subwoofer. If it's a 3-wire plug or a polarized plug, which has one prong wider than the other, you won't be able to reverse the plug. For safety, do not use a "cheater plug" to bypass the 3-wire plug.

With the power OFF, reverse the AC plugs one by one of any other components that have a standard 2-prong AC plug that isn't polarized. Each time you reverse a plug, turn on the system with the attached component and your subwoofer and see if the hum disappears. In some cases, reversing one or more plugs will eliminate the hum.

If you have a turntable, try connecting a separate ground wire to a chassis screw on your preamp or receiver and see if the hum disappears. If you already have a turntable ground wire, try removing it from the preamp. One or the other may eliminate the hum.

Finally, here is another solution that worked well for a member of our message boards who decided to discard his ground-loop isolator on his subwoofer: "I took off the ground-loop isolator I'd been using and connected a plain 14-gauge wire to chassis screws on the sub and the receiver then powered everything on. Although hum was still there, it was far lower than before. Next I unscrewed the ground-loop screw on the back of the sub and that took care of the hum completely."

Almost certainly sounds like an earth loop to me, but can be caused by a poorly made transformer or phase shifts on the mains supply. Visit some power conditioner web-sites like Isotek or Isol-8 (or google "earth loop") where there's plenty of advice on how to reduce/eliminate earth loops and other causes of mains-induced hum (transformer problems etc).

Hum on the speakers usually indicates that there is a DC voltage on the speaker line. DC voltage on the output lines would be caused by a shorted output transistor.


Have a nice day...

Feb 16, 2011 | Cambridge Soundworks BassCube 12 Speaker

1 Answer

Hi, I get a buzzing sound coming from my s8.3 when it's plugged into the power outlet. No other cable are connected, it's only plugged into power outlet. Any suggestions? thank you!


I also had a severe hum or buzz that was NOT a ground fault loop issue or any other such problem.

Hummed to the point that reading in the family room was annoying !

I took my amp to a Very Qualified shop and the technician simply insulated the transformer 40.00 usd

Nov 19, 2010 | Energry Speakers Energy Speakers S8.3...

3 Answers

Two speakers hum noise


Very doubtful that hum issue is ground potential difference from multiple power outlets as power cord is not grounding type (it is transformer isolated). I do agree that it is good practice to connect all audio equipment to common power strip though, especially with pro sound. Check the audio cords connecting your speakers to the coumputer sound card: 1) Make sure they are connected to the correct jacks and plugged in all the way, 2) wipe the connectors off with a clean paper towel wetted with a smidge of WD-40, 3) replace cords if all else fails. I have also seen solder joints fail on the power supply capacitors (due to vibration) causing hum -- but leave this repair to an electronics technician due to dangerous voltages.

Sep 25, 2010 | Altec Lansing AVS 500 Computer Speakers

1 Answer

My home theater speakers make a constant hum whenever my receiver is on. The loudness of the hum changes with the volume control, and goes away entirely when the system is muted. All components are plugged...


jd40,
Sounds like a grounding issue. The first two places to look into is the powered subwoofer and antenna. During your last test, did you leave the FM antenna and subwoofer connected? Many times the hum is directly related to the antenna and/or the subwoofer and to how they are grounded; creating a ground loop through the receivers ground on the outlet. If the antenna is grounded to the dwellings wiring, hum is inevitable and sometime you can get a ground loop hum from how or how & where the subwoofer is grounded. Try taking them completely out of the loop.

Also try taking it further back to the basics, start with the receiver plugged into a known good grounded outlet with no surge or line conditioner in the loop and nothing connected to the receiver, nothing. Use one speaker and different wire to test each speaker output while in tuner and any other mode but phono. With no signal, you will either get nothing (no hum or static) or just static in the tuner mode. No hum is a good sign. Some systems will mute the speakers if no signal is connected to eliminate the static from being produced through the speakers but a ground loop hum will most likely still be produced even in mute. If you get a hum when nothing is connected to the receiver, try looking into getting a better grounded outlet, even maybe to a different dwelling.

-Chris

Jan 30, 2010 | Yamaha 5.1-Ch. Surround Sound Home Theater...

2 Answers

Wharfedale 10inch cude subwoofer that has a feedback hum when con


Hiya, try a different input cable (from amp to sub) if you have make sure that is ok.

Failing that if there is an earth in the plug, try to disconnect that (earth loop) - unlikely but hey electronics.... anything possible :)

If still there with new cable, earth off etc, then the Yamaha could have a problem but find that difficult to swallow...

Let me know if helps, see any other possibilty
Best of luck

Jul 14, 2009 | Wharfedale PowerCube PC-10 Subwoofer

2 Answers

Hum


first of all you must connect as follows.
1-preamp/mixer-------equalizer/reverb unit------amp-----speakers(keep all equalizer control to 0db).
2-check your cables for good connector no touching of any inner wire to chassis of any equipment.
3-go to radio shack and buy(ground-loop isolator).
parts code(270-054)-----better to buy two pieces and connect it between your equipment.

Apr 01, 2009 | Audio Players & Recorders

1 Answer

Humming sound to speakers from amplifier


Hello,

It sounds like you may have a ground loop issue. I'd start by checking all the power and ground connections. Then disconnect the RCA wires from the amplifier. If the hum goes away then you should try grounding the stereo to a better grounding point, the factory grounds are usually not very good at all. Then try it again, if it is still there try replacing the RCA"s.

If the hum is still there after you've redone the connections and replaced the RCA's, you may need to install a ground loop isolator.
Both www.crutchfield.com and www.sonicelectronix.com sell good ones.

Hope this helps

Mar 28, 2009 | MTX X Thunder 1000XD Car Amp

2 Answers

BOSE 901V WITH EQ PIONEER XSV -95 RECIEVER.


Turn down the second amplifier (which the speakers are connected to). This hum is the amplified 'noise' from the EQ and/or amplifier. Try using a much higher graded second amp (eq 500w)

Mar 21, 2009 | Bose 901 VI Main / Stereo Speaker

2 Answers

Subwoofer probelm


I suspect you have a bad cable, a poor ground or a bad
power supply inside the speaker amplifier. The amplifier
(inside the sub-woofer) could also be defective.
===
1) Bad cable or connector:
If the (braided shield/outer tube) of the coaxial input cable is
not grounded, the cable will pickup line frequency "hum"
from surrounding power lines, house wires, lights and
appliances.

This hum is then amplified by the speaker's amplifier
causing the constant bass sound you speak of.

Because the hum frequency fundamental is 60 Hertz in
North America, 50 Hertz in Europe, you hear it coming
mostly out of the sub-woofer, because the midrange and
high speaker circuits filter it out.

Check the input connectors, cable at both ends, wiggle
the jacks at a low volume setting to see if it changes.

Make sure that you are indeed using a properly shielded
coaxial cable.

A coaxial cable consists of a thin inner conductor, surrounded
by a flexible tube made up of a braided metal shield, which
must be grounded. This prevents hum from being picked up
by the sensitive amplifier inputs.
===

2) If the power supply within the sub-woofer's internal amplifier
is defective, the the power supply hum will also get coupled
into the amplifier and speaker with same results as above.

Power supply hum is typically twice the line frequency,
i.e. 120 Hertz, but not always, depending on what
component failed: Rectifier diode, filter capacitor, or
the voltage regulator.

3) Ground loops:
When you run very long cables between the source and
destination of an audio signal, multiple ground paths (must)
exist between the two points in space, creating complete
loop circuits.

Power line hum from the environment can (will) induce
heavy AC currents around these loops, creating a voltage
gradient across these cables, and in-between the end
devices.

Once again, this AC hum is coupled into the amplifier inputs.

Ground loops become a problem with cables over 10
feet long, and an astronomical problem for stage audio
engineers. To avoid ground loops, they must break
the circuit's continuity by using isolation transformers,
optical isolators, and/or differential input amplifiers.

So how long are your cables?

Most house stereo components are only designed to
handle 6 to 10 feet of cabling max.

30 feet is already asking for major trouble.

4) Feed back oscillation: This occurs when the output of
an amplifier is fed back to the inputs with a round trip
gain greater or equal to unity. The tiniest little electrical
disturbance is then amplified and re-amplified, over and
over again, usually at one preferred frequency, causing
the typical (ear-splitting) microphone squeal or howl.

In your situation feedback and/ loss of original signal
could be the result of mis-wiring the input cables.

Note that this is NOT as silly nor as unlikely as it sounds,
because many computer audio cards and even some
home stereo systems have re-configurable inputs and
outputs.

SOFTWARE configuration decides which jack at the
back does what !!!!

On my computer, for example, the Realtek audio driver
tries to automatically figure out what cable is connected
to each jack (usually it gets it wrong)

Using the Realtek control panel applet, I can then
manually re-configure the gray jack as input,
the green jack as bass, pink jack as center.... etc.

If this situation also applies to your system, please check
the software configuration. Connecting an output cable to
an input jack will certainly cause a lot of HUM and not
much music.

5) Finally, don't rule out internal sub-woofer failure. Unlike
the passive stereo/hi-fi speakers of days gone by, modern
multi-channel theater systems with front, center, rear and
sub-woofer speakers are internally amplified, with active
frequency cross-over filters and special effect/ surround
sound capabilities.

Usually, the large sub-woofer contains most of the
electronics, amplifiers and filters.

It feeds the other speakers, and it is controlled by
an external volume control module which can be separate
or built into one of the tweeters.

These sub-woofer electronics are prone to poor design,
overheating and early failure. (Even fresh out of the box
like yours)

If you cannot get it working, take it back to the store,
and make the NICE salesmen **** with it.

Good luck
Please rate my answers
Martin.

Jul 20, 2008 | Yamaha 5.1-Ch. Surround Sound Home Theater...

2 Answers

RCA Pre-Out Making Producing a Mumming and a Popping Sound.


the speakers hook to speaker wires not to any thing else no power no negative poles do you have a remote shut off switch connected to amp this would be important to cut off amp

when cut off amp if you still here the humming this can be an indicator of low power being produced by alternator alternators produce 14 anything below 12 would mean replacement of alternator

if alternator fine then you need to find new ground for amp and make sure you have a good ground for sterio this can be checked with a test light
to check a ground all you do is hook gator clip to power then touch test light end to ground on radio end light comes on got a good ground (make sure not to touch any other sterio wires just the ground wire while connected to power to check grounds)
if pulsing in test light on the ground means you have a bad ground
just disconnect move to better ground

check the amp ground the same way as decribed above

May 09, 2008 | Pioneer DEH-P3900MP CD Player

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