New speaker issue

[Jon Fairhurst]

Nice. But you still get noise? Are you using balanced I/O and cables? You might try moving things around to see if there is a proximity problem.

You could also swap monitors left and right. Maybe one has a bad amp. Try swapping cables too.

If the noise is always on the same channel from the audio interface, maybe there is noise from the USB power source. Does it include an external power supply? You could try that.

If there is still a problem, the interface might be bad. Asus wouldn't have been my first choice. They're a fine motherboard company (I've bought a few), but they don't stake their reputation on having good audio. FWIW, I have a Focusrite Scarlett 2i4, which sounds great and has a great feature set. The 2i2 would be best for you as you probably don't need MIDI. The Focusrite Solo lacks balanced outputs, so I don't recommend it. The 2i4 adds MIDI, and the ability to mix the input and computer output, which is nice for multi-track recording.

Best of luck!

[Paul R Johnson]

Most of the reviews of that unit talk about how it drives headphones loudly, very few comments about audio quality. It's a gamer product, but still should be better than an internal card. How is it doing?

[John Willett]

Originally Posted by Richard Crowley

And portable "laptop" computers are even worse because of their external power supplies.

Yes - as I found recently when sorting a system for playing back evidence in a court trial - a horrible noise on the system that completely disappeared when the power supply was unplugged and the laptop was running on batteries.

Cured by changing the computer to another one.

[Renton Maclachlan]

I haven't had much time to check things out recently...tried shifting the speakers around and switching cables but it didn't seem to help. When the cursor goes down the Sony Vegas timeline and hits a graphic, the interference sounds like it changes gear...

It was suggested I try a USB isolator to run my USB DAC through... HiFimeDIY USB Isolator

[Renton Maclachlan]

Update...maybe of interest to some...

I've just been trying some things out tonight re this noise coming through my speakers….and think I may have found the cause or at least a cause...

Tonight the noise was only coming from one speaker that I could hear…and it was the same speaker regardless of which RCA lead was going to it. And it took a couple of seconds to start when playing down the Vegas time line. If I stopped the cursor and started it again immediately, the sound would start immediately. But if I stopped the cursor and waited a few seconds, it would not start immediately. That seemed odd.

However…the speakers were plugged into different power outlets…the one through which teh noise was coming was into one junction box, in close proximity to a ‘transformer/power supply’ driving speakers for my other computer, and the other into another junction box about a metre away from the other one…and which only has other plugs into it. When I plug power for each of the speakers into the latter junction box the present noise goes away.

I’m wondering if there were actually two noises…one coming from the computer power supply and one from this other power supply…or at least the junction box it was into - or something around there…[I have junction boxes galore to drive everything I have!!!]

So...maybe it is finally solved…hope so...and just after ordering a USB isolator!!! Probably won’t go amiss having the latter…

[Jay Massengill]

Hard to believe none of us remembered to re-state the "rule" about all parts of the audio chain being plugged into the exact same source of power, and with all wall-wart and line-lump power supplies placed as far away as possible using additional extension cords. Of course that won't automatically solve all noise problems, but it can eliminate one pesky variable.

I hope that's the end of your troubles!

[Paul R Johnson]

With our higher voltages in the UK, we've always had a slightly higher respect for mains power, but there's a creeping train of thought here that the old advice about running everything from one outlet isn't wrong - because it does often cure the problem, but worrying - because realistically, if something hums, it's down to current flowing somewhere it shouldn't. Years ago when people were stupid, people lifted the ground and hums went away. In the UK doing that now would be a major error, and if caught, trouble will follow. Grounds are for protection, and as many venue have testing requirements, or will test your kit before connecting - any cables with no ground, are going to generate a fail!

In a normal house (and I have to talk UK spec here, as I don't know the correct names for the US state of affairs) each socket is either wired direct to the consumer unit with MCBs in it, or runs in a ring out and back to another MCB. This here is the most common system. Actual distance of run is quite short, and in purely resistance terms, the ground of one socket should be as close to a short as is possible. Multiple earths are now quite rare, with most modern installations having the ground/earth tied to the neutral at the point of entry into the building, usually near the meters and consumer unit. With this kind of wiring, there really shouldn't be current flowing in the earth, and plugging into sockets in the next room should be hum and noise free. If it isn't, then something is not right, somewhere. Leakage, high resistance joints, who know?

Technical power supplies tend to be radial circuits - a common power supply fed individually to outlets, with each ground taken back to a dedicated earthing point, but with wall wart supplies, we really shouldn't be having as many ground issues as we do? All a bit odd.

[Rick Reineke]

As Jay stated, it's common practice (at least in the US) to power all the gear from one circuit to minimize the possibility of ground loops. And keep power supplies at a distance and never have power cables running parallel with audio cables. Any power/audio cable crossings should be done at right-angles. (another basic audio 101)

[Greg Miller]

Mr. Johnson,

This is most interesting but I'm a bit confused by your UK terminology. I would like to understand this better.

Let me share some US terminology and perhaps you can then offer a lexicon.

In a typical detached house (i.e. free-standing building, not part of a structure with multiple apartments inside) the service coming in from the utility company's pole is usually 240 VAC with a center-tapped "neutral" connection.

A metal box is mounted on the outside of the building with an integral meter socket, into which the utility company's meter is mounted.

National Electrical Code requires two metal rods (stakes) driven into the ground/earth/soil within a few feet of the meter socket. Ground wires lead from the ground rods to the meter socket, and inside the socket these actual ground wires are electrically connected (bonded) to the neutral wire coming in from the utility pole.

The two hot wires coming from the customer's side of the meter, along with the neutral/ground, are then carried to the interior of the building by a heavy cable. Inside the building, the cable goes into another metal box ("service entrance panel") which contains the main 2-pole circuit breaker, as well as the single-pole and 2-pole breakers for the various load circuits.

Inside the service entrance panel, the ground/neutral wire (from the meter socket) is connected to two separate metal buses: a ground bus, and a neutral bus. The load-carrying neutral wires that go out to various branch circuits (lights, small appliances, etc.) are white in color, and are all connected to the neutral bus. The safety ground wires that go out to the various branch circuits are green in color (or sometimes bare) and are all connected to the ground bus.

(Interestingly, our 120v circuits are all unbalanced with respect to ground, while our 240v circuits are all balanced. How does that compare with the UK?)

Perhaps you can help cross-reference some of this US terminology with UK terminology, and discuss any significant differences in practice. I am particularly puzzled by your terms like "consumer unit" and "MCBs."

--

Meanwhile, it's true that most older wall-warts should in theory minimize grounding and ground-loop issues. The exception would be those few wall-warts that do have a ground pin, in addition to the two current-carrying blades.

However, with many new wall-warts being high-frequency switchers, all kinds of strange non-sinusoidal waveforms are introduced into the power mains, and that can be a brand new source of noise ... and usually at frequencies that are much higher than mains harmonics so therefore possibly more difficult to filter out.

[Paul R Johnson]

Greg - I've sort of got used to using 'ground' rather than our 'earth', and most things are actually similar, but your service entrance panel is our consumer unit. Breakers appear to be a little different. The incoming mains L+N goes to a two pole switch, and then to the two busbars. Modern installs may replace the simple switch with two separate groups, each with a 2 pole switch. Ours look like this LAP 10-Way Fully Populated Consumer Unit Dual 63A RCD | Domestic Consumer Units | Screwfix.com


SKIP THIS NEXT BIT IF YOU ARE NOT INTERESTED IN UK ELECTRICS

Years ago, 45A was common as a maximum for a domestic dwelling, then it went gradually up to 100A now. MCBs - miniature circuit breakers, all to the European DIN size, and these just clip in. Our 3 pin sockets on a ring, are all 13A maximum, with fused plugs, and the ring is rated at 32A - we may have two, three or more depending on building size.

In terms of incoming cabling, virtually all private houses only have single phase electricity - so just L+N with 230V as our 'paperwork and calculation' voltage. In fact, it used to be 240V in the UK, and 220V in Europe. The EEC decided this was bad, confusing and unharmonised, so now we all use 230V. Of course, we didn't change the actual volts (mine is currently 243V, 50Hz) In the rest of europe, they still have their 220V - but Europe just fiddled the +/- allowance to make 230V the figure we all have to use. We use a star distribution system in the main - three phases, centre connected neutral, and phase to any phase is 400V (or 415 real volts!) Load is shared between the three phases as it passes down a road. Small workshops and industrial buildings get access to all three phases. We have quite a few actual input systems, but the three often quoted ones are:
TN–S
This type of electrical earthing system connects the neutral source of energy with the earth at one point only (or as near as practically possible), and with the consumer’s earthing terminal commonly connected to the metallic sheath or armour of the distributor’s service cable into the premises. With a TN–S the PE connection and N are separate conductors that are connected together only near the power source.
TN–C–S (PME)
A TN–C–S earthing system, typically known as Protective Multiple Earthing (PME), connects the supply neutral conductor of a distribution main with earth at course and at intervals along its stretch. The neutral conductor is also used to return earth faults currents safely to source by the provision of a consumer’s earthing terminal linked to the incoming neutral conductor.
TT
The neutral of the energy source is connected as with the TN–S system, however there is no provision for the consumer’s earthing, therefore they must provide their own connection to earth. This one isn't used in contemporary installs.

TN-C-S (PME) seems the most common now.

Distribution to areas is done at 11KV (or 6.6KV) using a delta system with no neutral - transformers then handle the conversion to 3 phase with neutral locally.

Domestic and small business premises don't usually have 3 phase electricity. 400V is seen as historically dangerous. It's not that many years since there were rules stating that if outlets on different phases were installed, there had to be at least 6ft between them, although that regulation thankfully went away. Clearly stuffing 400V down a cable is more of a risk, but I have dimmer packs that are three phase with multipoint connectors to the lighting circuits - and 400V between phases is maybe 8mm away!

Oddly - UK building sites require 110V tools and power for safety - cutting cables and exposing live wires. So they have to carry site transformers around.

That's a pretty quick run through!

One thing - we always do the cross at right angles recommendations, but you can now buy combined mains and XLR audio cables for powered speakers, which never seem to cause any issues! I suspect the right angle thing is perhaps now not really necessary.

[Greg Miller]

Paul, thanks for that exhaustive document. I'm on my way to work now but I'll try to digest it slowly and thoroughly later tonight.

A few quick questions:

You say "L+N goes to a 2 pole switch."

1.) In USA, "N" means neutral and is at ground/earth potential. Is that the same in UK?

2.) Does a typical residential house have just one "hot" line coming in, or two?

3.) *IF* your Neutral is at ground potential, does it still go through a switch in the "consumer unit" (entrance panel)? In USA we never switch or disconnect Neutral; in fact I believe it's illegal to do so.

I could go on and on, each question leads to another. It seems that "standard practice" is very different here from there, but maybe some of that will resolve when I come to a better understanding of all the details.

By the way, the 3-wire residential service I described above is called "split phase" because it is from just one phase of the high voltage distribution system. But it's center tapped so the 240 volt secondary is "split" in half. (The two hot legs are 180º out of phase with each other.)

In a bigger apartment building or commercial building, it's usual to bring in all three phases. Most newer construction is "Y" connected with the center of the Y being neutral/earth/ground. Any one hot leg is 120 volts above neutral. So if most of the loads are 120 volt, it's still possible to try to balance the phases. The voltage between any two hot legs is 208 volts (since they are 120º apart in phase).

Some older commercial buildings had a "delta" connection. Two of the transformer secondaries were simply 240 volts. The third secondary was 240 volt center tapped. That center tap was connected to neutral/ground. This allowed a true 240 volts on all three phases, to run higher-power loads. But only two of the legs could provide 120 volts to neutral. The third leg was high with respect to neutral and so could be used only with respect to the other two hot legs. Delta is always a PITA because of the potential danger with that high leg. Do you have such a thing? Was that explanation clear?

[Paul R Johnson]

I appreciate we've kind of hijacked the topic, but as tricks and tips for reducing electrical noise (and of course shocks) are handy and common, these differences might be useful - perhaps split out somewhere else?

At the point the supply enters the home, in most cases, the N- Neutral is bonded to the ground - which is then distributed from this point. The Live and Neutral BOTH go through the two pole switch, so with it off - there is ground at all outlets, but both L+N are isolated. RCDs are now quite common to give extra protection, downstream of the 2 pole switch.

Phase wise, we only have 120 degree phase shift. Occasionally, two phases may be in one building - if perhaps a domestic home is extended, and additional power is required, needing an extra feed from the supply in the street. Planned higher loads will be always 3 phase, with three phases and Neutral being brought in. Connector wise - we use similar looking ones for industrial applications CEE17 will bring up the common ones in Google - Colour coded for voltage - yellow 110V, Blue 230V, Red 400V - most versions of yellow and blue are 3 pin, single phase. Red has 5 pins - E (ground)-L1-L2-L3-N, although some motors will use a 4 pin Delta wired Red connector. There's even a similar purple one for less than 50V usage.

People who use video in the events world often have domestic 13A fused plug adaptors to 16A CEE17 outlets - as these are common in studios, theatres and other pro venues. (to confuse things, they come in 16A/32A/63A and 125A versions too!)

I believe there is a very similar looking connector used in the US as some of the lighting kit I have imported from China has a Blue connector fitted - but it's not our spec in size and pin spacing.

Quite a few of my colleagues have taken kit to the US and been able to find 230ish volts - and I could never work out how - Using the UK 3 phase system, on US voltages, I couldn't find a phase to phase voltage anywhere near 230 - so your split phase system, 180 degrees apart is totally new to me, and of course, the answer! Here, phase to phase connections are rare unless you are in big venues, but much more common in the US.

As another bit of history - our protection devices that monitored leakage to earth used to be a three terminal device, that measured how much was leaking to ground and used that to trip the circuit as the leakage must be a fault. Now, we normally use two terminal devices that monitor the difference between L and N, again, on the assumption that if they are not the same, it's going somewhere else - which is bad!

[Richard Crowley]

Its not all that mysterious. In North America, center-tapped, single-phase 230V is delivered to domestic customers and the center-tap is locally grounded and called "neutral". So typically half the 115V circuits in the house come from one side ("phase") of the transformer secondary winding, and the other half of the circuits are connected to the other side.

High-power devices (stoves/"cookers"), water heaters, etc. are designed to use 230V which is taken across the two "phases". I agree that use of the term "phase" for a simple center-tapped source seems rather pretentious. But that is what electricians have been calling it for several generations.

3 phase power is almost never found in domestic premises (homes, apartments, etc.) But it is commonly provided to larger industrial customers.

[Rick Reineke]

"Quite a few of my colleagues have taken kit to the US and been able to find 230ish volts - and I could never work out how"
- They likely tied directly into the main electrical breaker box which typically enters @ 220 volts / three phase, then broken out to multiple 110 volt two phase circuits that feed the US "Edison" wall sockets. Most lighting techs here as well tie directly into the three phase mains.

[Paul R Johnson]

It just never occurred to me that there was any other system than 3 phase - the notion of a centre tapped transformer just never occurred to me for mains power.