Checkout this article on Ground Loops - Eliminating System Hum and Buzz
Eliminating hum and buzz in music system
- Thread starter captrajesh
- Start date
My main takeaway from this article: "For example, if adjusting the volume on your processor/receiver does not alter the hum level, then the problem must be occurring after that point. It if occurred prior, then the receiver/processor would typically raise the overall level of noise. Make sense?"
Takeaway2: "When two or more devices are connected to a common ground through different paths, ground path noise, or a ground loop can occur. Thus, a system grounded at two different points, with a potential difference between the two grounds can cause unwanted noise voltage in the circuit paths. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment."
My recent learnings from personal experience about hum in analog chain: the tonearm cable which carries the very low level signal, which is of the order of a few millivolts, can be very vulnerable to inductive noise despite being shielded. The solution is trivial: lay the tonearm cable away from other power cables, and away from turntable motor, power supply units of preamps, power amps, and other devices.
You can identify this variety of hum induced in the tonearm cable by fact that it increases with volume, and can be easily reduced or removed almost completely only by re-laying the tonearm cable away from the above-mentioned noise sources.
Takeaway2: "When two or more devices are connected to a common ground through different paths, ground path noise, or a ground loop can occur. Thus, a system grounded at two different points, with a potential difference between the two grounds can cause unwanted noise voltage in the circuit paths. Currents flow through these multiple paths and develop voltages which can cause damage, noise or 50Hz/60Hz hum in audio or video equipment."
My recent learnings from personal experience about hum in analog chain: the tonearm cable which carries the very low level signal, which is of the order of a few millivolts, can be very vulnerable to inductive noise despite being shielded. The solution is trivial: lay the tonearm cable away from other power cables, and away from turntable motor, power supply units of preamps, power amps, and other devices.
You can identify this variety of hum induced in the tonearm cable by fact that it increases with volume, and can be easily reduced or removed almost completely only by re-laying the tonearm cable away from the above-mentioned noise sources.
That means, your other cables are getting equally loaded with the EMI/RF induced hum but is more evident because of the far lower strength of the signal flowing through the tonearm cable which gets amplified and manifests itself in demonic proportions when it comes out of, firstly at phono stage, then line stage and finally output stage.
I've talked to a couple of amp manufacturers on this and they have told me that apart from proper earthing etc you will have some hum sometimes (from tube amps for example). Some of them can silence the hum but only at the cost of sound quality. Basically if you have to place your ear right up against the speaker to hear the hum they prefer to just leave it alone.
In our Indian context, proper earthing is a real problem if you are living in a shared facility like an apartment. Even using an isolation transformer here will not help unless you have a proper earthing done. However getting an online UPS will clear up a significant amount of hash from your power source.
In our Indian context, proper earthing is a real problem if you are living in a shared facility like an apartment. Even using an isolation transformer here will not help unless you have a proper earthing done. However getting an online UPS will clear up a significant amount of hash from your power source.
greenhorn
Well-Known Member
If you have a vintage (20 or more years) device, replacing the capacitors in the power supply should help reduce hum/buzz. I had the recent experience with a tape deck 
Thad E Ginathom
Well-Known Member
In my first setup (amp+deck+cassette) I did not have audible hum, but I had a stong tactile hum ...the electrical buzz from metal cabinet parts. Cabinet to earth gave a noticable number of volts, I forget, maybe 20.
I have always found it necessary to earth a TT, else heavy audible buzz will come. In that case, I ran an earth wire from everything to a metal pipe that went to ground, which made the cabinets dead to touch again.
The only thing I winder about is... it was a gas pipe. Might I have been mad? As far as I can remember, in UK building, all metal pipe, gas, water, whatever, is electrically connected and earthed. Anyway, I'm still here, and the house is still there
I have always found it necessary to earth a TT, else heavy audible buzz will come. In that case, I ran an earth wire from everything to a metal pipe that went to ground, which made the cabinets dead to touch again.
The only thing I winder about is... it was a gas pipe. Might I have been mad? As far as I can remember, in UK building, all metal pipe, gas, water, whatever, is electrically connected and earthed. Anyway, I'm still here, and the house is still there
Also ensure that the inter connects ,speaker cables are not coiled and are run straight. If you have extra length trim it if possible or lay them straight. Do not coil the wires
Nikhil,
Let me clear out some mis-informations.
Don't expect HUM is always due to improper earthing, there are cases in which earthing or grounding is properly done but due to inherent flaws in power supply design and circuit design the system starts humming.
One such case is in Tube amps which has not seen the light of "how things should be done properly with modern technology", if a designer or manufacturer says that HUM has to be there else the sound quality will go low, then it simply states he is LACKING in expertise in solving the puzzle and simply don't know how to do it. As simple as that. Don't fall prey to such MORON product designers who propagate bullshit. Such misfits must be dealt with iron hand , because time and again they rob the innocent customers with their flawed design and convince the customer that hum is part of the sound character so ignore the hum.
I have seen well designed tube amps which have inaudible hum even if you place your ears close to the speakers.
If you use isolation transformer for the whole chain, you will not get the HUM at any cost. Only if the isolation barrier breaks through the chain you will get it, normally the HUM is not a problem unless there is a flaw in design.
Hum due to bad interconnects is separate issue altogether.
Let me clear out some mis-informations.
Don't expect HUM is always due to improper earthing, there are cases in which earthing or grounding is properly done but due to inherent flaws in power supply design and circuit design the system starts humming.
One such case is in Tube amps which has not seen the light of "how things should be done properly with modern technology", if a designer or manufacturer says that HUM has to be there else the sound quality will go low, then it simply states he is LACKING in expertise in solving the puzzle and simply don't know how to do it. As simple as that. Don't fall prey to such MORON product designers who propagate bullshit. Such misfits must be dealt with iron hand , because time and again they rob the innocent customers with their flawed design and convince the customer that hum is part of the sound character so ignore the hum.
I have seen well designed tube amps which have inaudible hum even if you place your ears close to the speakers.
If you use isolation transformer for the whole chain, you will not get the HUM at any cost. Only if the isolation barrier breaks through the chain you will get it, normally the HUM is not a problem unless there is a flaw in design.
Hum due to bad interconnects is separate issue altogether.
I was definitely not approving of hum and buzz "by design". To some extent I was referring to capable designers / mfrs who prefer not to use muting circuits in their designs because these affect the sound quality.
On the whole I agree with this but I'm not so sure that you can get that problem licked if you have a messed up earthing. As per an APC whitepaper on this: International office product safety regulations including IEC 950 and UL 1950 require that an isolation transformer is only allowed to isolate the hot and neutral wires; the grounding (Earthing) wire must be passed straight through ...
The most common example of this mistake is the purchase of a plug-in isolation transformer to solve a problem with ground loops or Inter-System Ground Noise. Isolation transformers have absolutely no effect on these problems because they are required to pass the ground"ing" wire straight through. Isolation transformers are frequently represented as providing an "isolated ground". What they actually provide is an isolated neutral or ground"ed" wire. This provides no benefit in solving ground"ing" problems, which are the primary cause of power problems.
Nikhil,
I would love to know about what type of "muting circuits" these capable designers employ in order to mute the HUM. Also would like to know if these muting circuits work on HUM originating from earthing mistakes or circuit design mistakes and their effects on sound quality. Kindly shed some light.
Why i am curious to know about this because, there is a hidden technical flaw inherent in the statement from so called capable designers. I would be glad to learn more about this.
APC is just telling about a particular case of one isolation transformer in which GND connection is as it is, not eliminated.
What about the isolation transformers in which there is a provision to eliminate Earth connection between earth terminal of wall socket i.e. primary side and secondary side winding center tap[sometimes these are also called balanced isolated transformers]. In such case you cannot get a ground loop at all.
Cheers,
Kanwar
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theraindew
Member
My tube amp has no hum whatsoever.
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