a little bit of humm.......

[emperor]

Hi guys, Ive got a hum problem, just need some feedback, i am currently monoblocking, Monobridging two Behringer A500 *pro Amps, and on the left channel i seem to be getting some hum. I have it in a system with a rotel pre amp, Cd player, turntable, Cassette deck

Before i say any more, sometimes i run my finger along the front of my Cd player and amp which is metal , and there is a small voltage ,static running across them. I have a small studio, and the hum is present in there, also downstairs it happens to the hifi in the front room. a small charge at times. My television upstairs has the same background interference. I have had that for 4 years, and beforehand a Audiolab 8000SX times 2, and that never gave off hummed so much.

anyway any info ideas, could be poor grounding in the power amp, the interconnects, i have unplugged everything , interconnects and all

So maybe a ring main problem? Its a bit of a lottery really.

thanks for any info

 

[agarwalro]

Ive got a hum problem, just need some feedback

In the first sentence you indicate the symptom and the cause of the problem. That funny. The problem is that your ground "signal" is looping from one device into the amp and causing a ground feedback hum (about 60Hz). EDIT: Just noticed that you are in England. In your case, the hum clocks in at 50Hz.

Start with all devices plugged in, powered up in idle state to hear the hum. Keeping the amps plugged in, start disconnecting other devices one at a time. If you remove a device and the hum does not stop, plug it back in. Repeat till you have isolated the errent device(s).

This(these) device(s) will have to go on a differenct circuit in your home or you will have to place an isolation transformer between this device and the rest.

Hope this helps.

 

[emperor]

Thanks i appreciate your help Agarwalro , i did actually just take every plug out of its socket, one by one, in the end I just plugged the offending power amp in to one main socket on its own, it hummed like crazy.

But it is connected to my pre amp, so i thought, ok, i will connect it to another preamp, and the same thing again, same hum. I connected it straight to my CD player, wherever i connect it, the hum remains, could it be a grounding issue in the Amp you reckon, the interconnects not grounding.

I wont do this, but what if i disconnected the ground wire in the plug?. I only had an afterthought, as i think i might have heard it somewhere else a while back, all the same i wont, unless i ever knew it was 100% right.

Any ideas ??

 

[agarwalro]

Under no circumstance should you remove the ground conductor from the amp plug. If for some reason you have a short or if a loose power or cap wire inside the amp is touching the case, you will get a potenitally FATAL shock.

 

[agarwalro]

A pertenant excerpt from here, Interconnects and some more info can be found here Ground Loop

Almost all cases of noise can be traced directly to ground loops, grounding or lack thereof. It is important to understand the mechanism that causes grounding noise in order to effectively eliminate it. Each component of a sound system produces its own ground internally. This ground is usually called the audio signal ground. Connecting devices together with the interconnecting cables can tie the signal grounds of the two units together in one place through the conductors in the cable. Ground loops occur when the grounds of the two units are also tied together in another place: via the third wire in the line cord, by tying the metal chassis together through the rack rails, etc. These situations create a circuit through which current may flow in a closed "loop" from one unit's ground out to a second unit and back to the first. It is not simply the presence of this current that creates the hum—it is when this current flows through a unit's audio signal ground that creates the hum.

 

[agarwalro]

And some suggestions on what to do to fix the hum can be found here, Hum removal

 

[mtrycrafts]

Hi guys, Ive got a hum problem, just need some feedback, i am currently monoblocking, Monobridging two Behringer A500 *pro Amps, and on the left channel i seem to be getting some hum. I have it in a system with a rotel pre amp, Cd player, turntable, Cassette deck

Before i say any more, sometimes i run my finger along the front of my Cd player and amp which is metal , and there is a small voltage ,static running across them. I have a small studio, and the hum is present in there, also downstairs it happens to the hifi in the front room. a small charge at times. My television upstairs has the same background interference. I have had that for 4 years, and beforehand a Audiolab 8000SX times 2, and that never gave off hummed so much.

anyway any info ideas, could be poor grounding in the power amp, the interconnects, i have unplugged everything , interconnects and all

So maybe a ring main problem? Its a bit of a lottery really.

thanks for any info

Besides what you already tried and was suggested, have you unplugged the TV totally, including the antenna connection, especially to any audio gear? If not, try this as well. Many ground loop issues in the states can be traced to the cable TV feed. A ground isolator for the cable is available.

For that 220V power line which caused a bigger hum, you could temporarily try a cheater plug but not as a cure.

Have you tried to tie a separate ground wire to all the components chassis?

 

[emperor]

Well thanks for all your help, i have posted on many forums , about the problem and many people have come back with really good advice.

I have now Just unplugged every bit of eqpt , with just the "one", power amp, still conectted to the pre amp, unplugged, (From the mains), and intercoonectd still to the other power amp(unplugged), on its own it hums like crazy, its like it cuts down the ground hum, if i plug the other one in and turn it on. I hope that makes sense.

Im wondering about buying a Russ Andrews "silencer", wether that may work. I mean i have had the static charge for years and its not made a difference, to my audiolab 8000SX,s power amps i had previously but, maybe monoblocking, adds to the noise and doubles it.

I may have to get an electrician to do some readings, also Perhaps some grounding ideas for the chassis.

these Behringer A500 pro amps, at least do have a gain output so i do turn it as low as possible, in order for the hum to not be overbearing. But enought to drive it at moderately high levels

It also doesnt matter what i plug it into, Cd player, Different preamps, always the same hum, the other Channel, and power amp however is as silent as anything.

once again thanks for all the great ideas/advice.

By the way, im in the UK, on 240 volts

 

[mtrycrafts]

Well thanks for all your help, i have posted on many forums , about the problem and many people have come back with really good advice.

I have now Just unplugged every bit of eqpt , with just the "one", power amp, still conectted to the pre amp, unplugged, (From the mains), and intercoonectd still to the other power amp(unplugged), on its own it hums like crazy, its like it cuts down the ground hum, if i plug the other one in and turn it on. I hope that makes sense.

Im wondering about buying a Russ Andrews "silencer", wether that may work. I mean i have had the static charge for years and its not made a difference, to my audiolab 8000SX,s power amps i had previously but, maybe monoblocking, adds to the noise and doubles it.

I may have to get an electrician to do some readings, also Perhaps some grounding ideas for the chassis.

these Behringer A500 pro amps, at least do have a gain output so i do turn it as low as possible, in order for the hum to not be overbearing. But enought to drive it at moderately high levels

It also doesnt matter what i plug it into, Cd player, Different preamps, always the same hum, the other Channel, and power amp however is as silent as anything.

once again thanks for all the great ideas/advice.

By the way, im in the UK, on 240 volts

Well, if that amp has that buzz on its own, nothing plugged in, it has an issue. Have you called Behringer?
A separate ground from the chassis? You shouldn't have all that problem.

 

[Malice]

Under no circumstance should you remove the ground conductor from the amp plug. If for some reason you have a short or if a loose power or cap wire inside the amp is touching the case, you will get a potentially FATAL shock.

Not necessarily the case in the UK, as many newer homes have RCD inbuilt on the mains boards. Equally if there is no RCD on the main board you can use one of those plug-in RCD types that get used on electric mowers for use in the garden. These protect the user in the event of an earth malfunction by monitoring the current in the live and return circuits. A drop of a few mA will trip the switch thereby preventing any "FATAL" shocks.

I had a hum on my Behrinnger BFD with my SVS sub. Disconnecting the earth solved the problem and I have no issues with relying on RCD technology to protect me from any faults.

HTH.

 

[emperor]

thanks very much Agalwalro,(very good tips) Mytcrafts, (no i have not got in touch with behringer yet, as im not sure that its the sole purpose of the hum, but will, if after the electrician comes,*more expense grrr*, and finds its a problem.

And also thankyou malice for your advice. Im still no nearer at the moment to finidng out what it is, i have about 8 people telling me different things, the noise problem im sure is with the way the Behringer power amps, are working with each other. So I hopefully will get an electrician first, and then if he cant do too much about it, well **** knows.

Always had the static problem before, with the electric, but never the hum, now withing the hum, i can pick up the radio!!, odd.

your right malice, not every peice of eqpt i have has an earth.

i have found the Earth to the house, and its situated on a copper pipe under the sink, looks intact,though. Was wondering if a Russ Andrews "silencer" might work, or help.

Also the Behringer Amp, as its a Pro audio Amp, has gain controls, so I have turned the gain pot down, In normal stereo you use the two gain pots for each channel, but with the bridged mono, you use, one pair of inter connects, one for the left amp, and one for the right amp, and only the left gain pot is in use for mono operation.

Is it better to use headphones and chuck them in the bin?

 

[mtrycrafts]

your right malice, not every peice of eqpt i have has an earth.
(

That is because their body is better insulated between the user and earth.

 

[emperor]

Well, dare i say i got to the route of the*audio* hum, I took the interconnect to peices and it wasnt grounded, one of the wires had snapped off to the outer Earth cable, weird as i swear i had checked it first and it was intact. all the same, it has cut the hum by half(barely audible with the gain pot at half), down to an acceptable level. I say *audio* hum, but there is still some, issues with the electricity. It has been like it for years in this house, so im still getting an electrician to look at it.

see what this small voltage is. But im waiting for funds to develop before i can afford one to come out. all the same im pleased my Amp is not faulty, and that i can listen to low level music at night with near silence, bliss!!

 

[mtrycrafts]

Well, dare i say i got to the route of the*audio* hum, I took the interconnect to peices and it wasnt grounded, one of the wires had snapped off to the outer Earth cable, weird as i swear i had checked it first and it was intact. all the same, it has cut the hum by half(barely audible with the gain pot at half), down to an acceptable level. I say *audio* hum, but there is still some, issues with the electricity. It has been like it for years in this house, so im still getting an electrician to look at it.

see what this small voltage is. But im waiting for funds to develop before i can afford one to come out. all the same im pleased my Amp is not faulty, and that i can listen to low level music at night with near silence, bliss!!

Hey, that is great. I bet that cable was fine then the cold solder separated for good.

 

[emperor]

I have to say after getting rid of the Hum, its the first night, tonight i did some serious listening, i upgraded the opamps in my AH tubed CD player, BB OPA627AP, and it sounds really exciting and musical. The monoblocked Behringer a500's sound so supreme, its better than my Audiolab 8000SX/8000C, triamp setup, no bullshit, sounds the best ive ever had. For the money, i cant praise it enough.

(lived a sheltered life). No have heard many a system, from budget to high end, even my own music used on passlabs and AH, Krell, conrad johnson, wilson benesch setups...lift music.

The control and the soundstage on excellent recordings, is really something.
I feel now im on the lower wrung of the high end soundstage. Pace timing, Depth, clarity, the spaces and the placement of instruments, the timbre of live intruments, and sounds is something you can walk around. All with eerie realism. The ambience is absolutely top class. And even at the higher levels its never fatiguing. Might be the tube effect of the CD player, but compliments these lush sounding monoblocks

I had a pair of standard dull black Tannoy MX4M's, and then decided to iron on some teak Veneer, (cause i loved them), and finish with Danish Oil. Also silverwired with QED silver anniversary speaker wire, from the crossovers to drivers throughout.

They sound better than my old Acoustic energy Ae120's costing £500 .
the MX4M's were a snip at £250, (was £350 retail). Absolute bargain. I may have mentioned I had a Rotel RC960BX pre Amp, that also has had an opamp upgrade throughout. That was bought £40 secondhand off ebay. Has the MM/MC phono inputs for my Rega planar 3 which is handy.

So all In all, Its proven to me i didnt have to spend a horrendous amount of money to get a good quality sound. I may have been extremely lucky in matching components, and the luck of the speakers being good for what they are, such a transient immediate response, for budget cinema floorstanders, control is brill. The Kingpins really are the monoblocked A500's, they are quite stunning value. Not forgetting the excellent Van Den hul DM102 3 throughout, (bought secondhand), great cable.
Dare i say im happy, is the upgrade bug still there, yikes, yes it is, im now looking at silver wire speaker cable. (Least i am enjoying the music a lot. lotmore)