Karaoke Forums

Unnecessary?--Yes.

Maybe that's just for me.
Then I do electronics. It helps.

Ebtech - unecessary - Maybe, but does work in a pinch (safely) for those that do not have time to track down the source.
An external USB I/O interface will also many times eliminate the hum of a laptop, my HP laptop had a huge hum going through the headphone output (plus just didn't sound that great), I run the Lexicon Alpha & the hum is gone PLUS the sound is much more in the pro sound catagory.

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LIKE Lonman on Facebook - Lonman Productions Karaoke & my main site via my profile!

http://www.hark.com/clips/pbphqpysjp-youre-a-smug-unhappy-little-man


we may be too stupid and lazy to figure out the hum, but we are on the tommyboy side of this quote!!

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[glow=red]Yo sucka, we need this hea CHOPTER, and we need it now![/glow]

Like I said doing electronics helps.

Look mate, just write down your complaint
and mail it to the Easter Bunny.

who needs the easter bunny when you have the humX ??

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[glow=red]Yo sucka, we need this hea CHOPTER, and we need it now![/glow]

Yes mate.
You are right.

Not ashamed to admit, I use the X.

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KingBing Entertainment C'mon Up! I have a song for you!!! [font=MS Sans Serif][/font]

Just to add my 2 Cents, I too had this from the House TV, and while isolating components, I discovered when I disconnected my Video (RCA) connector from the TV I lost the hum.

The RF coax was connected as well, so I disconnected the RF and reconnected the Video connector; again, No Hum. So apparently the potential ground difference carried back through the video cable to my karaoke player and dispersed from there.

It also should be noted that the TV was plugged into a different power source.

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EveningStar Entertainment & Events
JR & Michele LaPorte
Peoria, AZ

You know, I don't know whether to put this here or start a new thread, but it is really important for people to understand what a ground connection is/does and how it's used in electronic equipment.

I think most people know that the ground connection in electrical components is there primarily as a safety feature. Equally, I think most here understand that electricity will always flow to the easiest path it can find to the earth (ground - hence the name). The ground connection is meant to be the easiest possible path to earth so that if any compoenent of an electrical appliance were to fail, that any stray voltage would find the earth through that connection and not the body of a user of the appliance. This is why if you open up most electrical or electronic appliances you'll see that the ground wire is connected directly to a metal piece of the chassis of that equipment. This is how safety is ensured, since that ground connection will always be an easier path to earth than the human body touching the chassis. So that covers the electrical supply.

Now, how does this affect audio/video systems. Almost all audio and video systems use the ground as a reference (much like the neutral leg of an AC power supply). When the electrical potential of the "hot" leg is different from that of the reference, a voltage (flow of electrons) is produced and this voltage is the signal that they then process. If you look at all the connections for audio and video on any of your components you'll find they they all have a connection to ground. In VGA, Pins 1&2 are the ground reference, for 1/4" and 1/8" TR and TRS connections the "Sleeve" conductor is the ground, Pin 1 in XLR is ground and even USB has a ground connection on Pin 4. These ground connections ultimately connect to the chassis of each piece in the chain. So the end result is that there is one common connection along ground between every component in your system. This is the key, because here's what can happen.

Say I have my entire system plugged into the same power strip except for the bar TV that I connect to using an RCA cable. I then find I have a ground loop issue coming from that TV which is plugged into a different outlet. I can't plug that TV into my power strip so I put a 3 prong to 2 prong adapter on my power strip without the ground tab connected. Boom, no more ground loop hum. Great right? Wrong. What happens now if my amplifier fails and 110VAC hits it's chassis. Well it's going to find the easiest path to ground. So its going to flow back through the ground connection of the XLR's from the amp to the mixer, then through the audio cables to the laptop, then out the RCA port's ground, through that RCA cord, to the TV and finally to the ground connection.

Now think about this, do you want that voltage traveling through all those components of your system? Do you want that voltage traveling through all those extremely small gauge wires that are only meant to carry mili-volts of electricity and milli-amps of current? The probably of equipment damage and fire is astronomical. Now instead if that power strip were properly grounded, the voltage would have traveled from the amp, to the power strip to the ground and out to earth, never touching any other equipment or wiring not meant to carry that amount of electricity.

THIS is why breaking off ground pins is extremely dangerous. This is why it is important to understand this stuff. This is also how you can quickly and easily diagnose and resolve ground loop issues without isolation transformers like the HumX. This is also why you want to be very sure that such an isolation transformer still has a low-enough resistance such that it will not prevent a full discharge along the ground path. Food for thought folks.

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DJ Tony
Let It Rip Karaoke

2 main types of power supplies. Transformer and switching. Most amps use transformer PS but not all. Almost all PCs, laptop and desktop, use switching PS. Only very old TVs use transformer PS. Meaning new TVs use switching PSs and have no ground plug only power and return. But they do have fuses (all do) and limiting resistors which will burn out if the main power aproaches a short condition. Meaning resistance is very small or none between power (120vac) and return. Remember they have no true ground going to the 3rd prong on a plug.

Transformer PSs all have grounds which come off the center tap of the input coil. Low voltage switching PSs may not have ground plugs but all high voltage switching PSs have grounds. But it really does not matter if they have grounds or not. The output power and returns of these switching PSs pass to the circuit to be powered without earth ground, they use reference ground(circuit to circuit). Should something short on the output and feedback on the Switching PS it will CROWBAR meaning shutdown. Now I am not going to go into what causes a crowbar condition or how it can be removed but this shutdown will stop the device from burning up and most times stop any damage from occurring!

Now I understand most don't know the difference between the PS types. Yes your power amp along with your mixer may feedback serious voltages and hurt a person at a mic or Kj at the amp but this is the true reason for earth ground (3rd prong). Reference ground is used between devices such as PCs, TVs, interfaces to the mixer, from the amp to the speakers and the other devices used by the KJ. Some devices allow you to connect their reference ground to earth ground but not all.

Now you get hit by a lightening strike or powersurge then anything can happen but just a device going bad is not going to take it all out just as earth grounding all things may or may not fix your problem!

Hmmm... Workmen.
You seem to understand but I think you could put it across
in a way that people could understand better than you did.

Oh and If your Amplifier is heavy it uses a transformer. (Heavy copper windings)
Always uses an earth. Often has a ground lift.
If it is light, it uses a switched mode power supply. (Electronic components)
All desktops, laptops and monitors use SMPS.

What you put was not understood fully by me and I know it..
Take another go at explaining.
Don't assume. Write a good foolproof explanation for people that don't understand.
In a way that they can follow. You can do this.
You may even devalue the Humx by helping these guys on the forum.

The aim here is a good one.
It is to help you understand what you are doing when you connect electronic gear together. It will tell you why hum is happening and how to remove it.

@ Workmen

Great description of power supplies but doesn't really even apply to the discussion at hand. VERY FEW devices allow you to choose whether reference ground is common with your supply ground. Take a look at a mixer for instance. The chassis is grounded to the supply ground right out of the shoot. What do all those nice quarter inch jacks have in common? They're all mounted to the metal chassis with metal nuts and washers and those metal threads are part of the sleeve of the jack which is directly in contact with the sleeve contact of the cable. BTW, if you open it up and look at the XLR's, you'll find that all have Pin 1 attached to the chassis for ground as well.

Now as far as switching versus transformer, I don't know why you bring that up but it's pointless in this discussion. Again, with the common ground, even if your laptop is using a switching supply that is not grounded, the chassis and everything that use reference ground are bonded together so any connections out with a reference ground (including the headphone jack, VGA/RCA jack, USB ports, whatever) will now link ground through those cables to the next component down the path (say an earth grounded mixer) giving them now a true connection to earth.

The situation I described in the last post wasn't something I made up, it was a real world situation I've encountered now in two separate bars. The only difference, other than one time for troubleshooting purposes only, I don't use the 3-prong adapter. Try it for yourself, you can find very easily that the ground across all components IS indeed common. Hard to believe, maybe, but it's true nonetheless. Just like programmers, systems designers get lazy. Bonding all grounds to the chassis is the easiest way to ensure consistent ground throughout the device. The problem is it continues the ground path as I've described. Fully isolating electrical and reference ground is more expensive and complex, so it's rarely done, especially in the level of equipment we're talking about here.

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DJ Tony
Let It Rip Karaoke

jerry12x

It is outside the limits of this forum to fully explain grounding and power suppy workings. So I shall attempt to make my points within limits.

Switching PSs are used in newer equipment because they are light and will maintain their output voltages with wide tolerance to input ac voltage usually between 88vac and 132vac. Where as their counterpart the transformer ps will brownout (with low voltage) or encounter damage with higher than normal voltage. Voltage swings are applied directly to the PS output stages with transformer PSs.

Transformer weight is mainly due to the iron cores plus the copper that is wound around these cores on the input and output windings.

A diode is a device that lets electrons flow only one way and not the other. If 2 diodes are connected in opposite directions to the ends of the transformer secondary it forms a half wave rectifier. If earth ground is applied to the negative diode end (the diode which is connected in the circuit to pass negitive voltage) the voltage between the other diode end will be a positive output. If connections to the diodes are reversed the output voltage will be a negative. If no earth ground is connected then the output polarity is determined by the connections to the using circuit. This is called reference ground.

example:

supply 1 outputs -7v dc referenced to earth ground
supply 2 outputs -12v dc referenced to earth ground

With supply 2 connected to reference ground (black lead) of a +5v motor and supply 1 connected to power (red lead) of the same +5v motor +5v dc is supplied to the motor and it turns. NOTE: +5v dc was generated from two negative supplies!

Most of todays devices use reference ground instead of earth ground because power potential (difference between reference or circuit ground and supplied voltage) stays the the same even when input voltages go up and down. Earth ground is only used to drain off harmful voltages to protect humans.

As I stated switching Power Supplies are very input voltage tolerent but internal circuits of devices used in karaoke are not. So as inputs vary the voltages used in the component circuits must not. To provide this reference ground is used. The circuits pass this reference ground from device to device via the signal return line. So the signal goes out on one line and its return brings it back to the originating circuit. But the circuit it feeds uses the signals return line as a reference ground.

It is here that the feedback (HUM) can occur! If a device using reference ground is connected to a device which has a bad connection (increased resistance to reference ground) then the potential is less than it should be and reduction of signal occurs. If this reduced potential is applied to an amplifier circuit it will cause feedback (HUM)! If you have a TV which is connected to an earth grounded block as most cable and sat systems are you may or may not get a decrease in potential (feedback or hum). BTW the cable and sat receivers are NOT connected to earth ground to prevent feedback (HUM). It is to short lightening strikes to ground!!! Also applying earth ground to some devices will cause the switching power supply to CROWBAR (shutdown). A HumX simply transformer isolates input power. Isolated you have reference ground and still maintain the ability to short surges to earth ground thru other components, transformers will pass power either way depending on potential!

On second thought, just not worth any additional reply.

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DJ Tony
Let It Rip Karaoke

Missed the point mate

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