( hoping this helps someone(s) ) Best, or at least good, practice suggests ensuring you use a single earth ground. Practically this means using a single receptacle with a power strip with enough receptacles for all your equipment. This model forces separate ground paths for each device to a single, common grounding point. (15 amps at 110VAC is usually enough power for a band and PA and recording equipment; think of the entire setup as a single device comprising amps, mics, outboard equipment, mixers, and so forth: all one frankenstein device.) Given one single common receptacle for all power, then the earth ground wire properly connects to the frames of the devices so that the cases act as a Faraday cage, capturing EMF (e.g. from fluorescent lamps) and shunting that kind of noise to the earth ground point on the ground (green or bare copper) wires not shared by the devices' power supplies. Note that both balanced and unbalanced signal cables connect to device frames, and therefore to earth ground. In the case of balanced cables, the frame connector (the sleeve for phone plugs and pin 1 for Cannon XLR three-pin cables) extends the Faraday shield of the frame to the sheath conductor over the two signal wires. In the case of unbalanced cables, there is only one signal wire (tip of a phone or RCA plug); the sheath conductor provides a current path for both the signal return and the earth ground. Balanced is better, if possible. Regardless of balanced or unbalanced, there is a nuance to keep in mind: ground loops. A ground loop is a current path to two different ground connections. Ground loops can be the reason noise enters the signal paths; ground loops may also be the reason for annoying shocks to humans. For electrical power connections, using two different receptacles risks having two different ground points (even if ultimately the grounding wires connect to the same earth grounding lug). If there is a difference in length or the number of connections in the two ground wire paths, then it is likely that some impedance difference is presented to each of the receptacles, and therefore a voltage difference between the two receptacles' ground lugs. For signal connections, consider the case of routing a signal from some source to some device and from that device to another device (chaining devices). Note that the frames of all devices are connected through the signal wires' sheath conductyors. If each device has a separate power connection, there may be an impedance (and therefore, voltage) difference between the ground lugs of the two devices, and therefore between the two devices' frames. If so, there may be electrical current between the two frames. This current may be that of low voltage but high frequency noise that may bleed into the power supply and thence to the signal circuitry, or it may be high, out-of-phase power voltage current (which likely will trip the breakers or fuses--if not, this presents a truly dangerous shock hazard to humans). If you're using unbalanced cables, then your only fix is to lift the ground of the power cables for all but one device so that all the other devices must make their connections toground through the sheath conductor of the signal cables. If you're using balanced cables, then you can either use the above approach or you can add an insulating device to the signal cables' sheath ground such that the signal cable connects all three pins (or tip-ring-sleeve) to one device but only the two signal pins (or tip-ring) to the other device. This lets each device extend its frame grounding over its inbound cable (or outbound cable, either one, not both), and the ground connector at that device's output cable connection has insulation to disconnect that device's frame ground from the sheathing of its outbound cable (which in turn gets connected to the next device in the chain and its frame). Thus any differences in frame ground voltages between devices have no way to flow to adjacent devices (e.g. microphones). On 02/08/2015 10:57 AM, Ralf Mardorf wrote:

On Sun, 08 Feb 2015 21:14:12 +0100, Hermann Meyer wrote: Actually I'm living in an "Altbau" with retrofitted concrete-footing ground electrode. Potential issues could be caused by tons or grotesque reasons. Reality has absolutely nothing to do with school books.

On Sun, 8 Feb 2015 15:52:43 -0500, Gene Heskett wrote: The German term is "Fundamenterder" and it comes with a "Potentialausgleichsschiene". We have a DIN norm for protective earth neutral Fundamenterder with Potentialausgleichsschiene. The translation to "concrete-footing ground electrode" isn't perfect. On Sun, 8 Feb 2015 15:32:02 -0500, Gene Heskett wrote: That's the problem, there are always "unknowns".

On Sun, 08 Feb 2015 13:28:17 -0800, jim wrote: You might have noticed that my English isn't that good, perhaps somebody is able to translate what the German Wiki says. It would be much better to translate the DIN VDE. All in all there are issues, such as interaction of ground systems. So there's no security. In fact you should ask your local electricity provider to do measurements from time to time, but nobody does, since it's not for free. What's working today could be damaged next week. The DIY market tool to check ground is not good enough. Potential equalisation minimizes potential difference, but the potential difference might not be zero. Time for a real time-out. But I guess this topic was too important to not breathe a word. Regards, Ralf http://de.wikipedia.org/wiki/Potentialausgleich "Potentialausgleich bezeichnet eine elektrisch gut leitfähige Verbindung, die unterschiedliche elektrische Potentiale minimiert." http://de.wikipedia.org/wiki/Erdung "Nur in statischen Anwendungsfällen darf daher davon ausgegangen werden, dass mit der Erdung jegliche Potentialdifferenz ausgeschlossen ist." "Aufgrund der Vielzahl von unterschiedlichen Erdungssystemen kann es zu Beeinflussung der Erdungssysteme untereinander kommen. Dieses macht sich besonders in städtischen Gebieten mit dichter Bebauung bemerkbar, wenn Bahntrassen in der Nähe der Bebauung verlaufen. Durch Potentialverschleppungen kann es zu Überlagerungen des Bahnstromes auf das Drehstromnetz kommen. Dies führt dazu, dass Anlagen nicht mehr einwandfrei funktionieren. Im schlimmsten Fall können diese Überlagerungen zu Schäden am Erder führen oder sogar den PEN-Leiter zerstören. Durch vagabundierende Gleichströme kommt es in der Nähe von Gleichstrombahnen zu starken Korrosionen an Erdern aus feuerverzinktem Stahl. Über die Erdung ins Erdreich eingeleitete Wechselströme führen über längere Zeit zu Korrosionen an Rohrleitungen. Dies wirkt sich dann besonders aus wenn Rohrleitungen als Erder genutzt werden. Prüfung Das Vorhandensein eines Anschlusses zu einem Potentialerder allein bietet noch keine Gewähr für dessen Tauglichkeit und eine sichere Erdung. Daher muss nach dem Einrichten eines Potentialerders eine Prüfung auf Ableitung von Fehlerströmen nach VDE 0100 usw. erfolgen."

On Sun, 8 Feb 2015 20:53:28 +0100, Ralf Mardorf wrote: IOW care about creeping current from washing machines and dishwashers and similar issues. My dishwasher does suffer from creeping current. You can measure it, but you don't get an electric shock. However, things similar to that and other strange seed happens in reality. Ground between two mains sockets very often is not neutral, for what reason ever. We are living in a real world, not in school.

On Sun, 2015-02-08 at 15:32 -0500, Gene Heskett wrote: While I agree in principle, if you play in the New Orleans area you'll starve. I don't think there's a building in any of the old sections of NO that is wired to code. I've been zapped so many times that I'm beginning to glow in the dark ;-)

On Sun, Feb 08, 2015 at 08:08:23PM -0800, Len Ovens wrote: And that's the only right thing to do. Re. putting 10 ohm resistors in the ground connection: if you have two different ground voltages they are likely to be low impedance (if not a good cable connecting them would remove the problem). Assume you have 10 V difference and that the impedance between the two grounds is 10 ohm as well. Then we have 20 ohm total, and a current of 0.5 A. That's 2.5 Watt in your 10 ohm resistor. Which means it will first turn red and then and self-destruct in a puff of smoke. Unless it's a really big resistor. The only solution if you can't have a common ground is to use transformer isolated balanced connections, this allows you to disconnect ground at one end and still have a signal. Without the transformer isolation you could easily blow up either the output or the input, or both. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow)

On Sun, Feb 8, 2015 at 3:57 PM, David Christensen <dpchrist(a)holgerdanske.com ​Just wondering on all this ... where the grounding is "suspicious" does the use of a ext. chord with a built in GFI switch add any safety? Probably doesn't solve grounding loop problems. -- **** Listen to my FREE CD at http://www.mellowood.ca/music/cedars **** Bob van der Poel ** Wynndel, British Columbia, CANADA ** EMAIL: bob(a)mellowood.ca WWW: http://www.mellowood.ca

On Sun, 8 Feb 2015, David Christensen wrote: All I know is I put 10ohms in series with the ground line and the hum got much worse. I want yes :) Right now I don't have. The snake is old and the monitor returns are signal and ground :P All of our balanced stage equipment uses a DI with isolation transformer. The monitors are an old peavy, that is so old I can't even find mention of it on the peavy site. (I had the model written down but have lost it) It is from the dawn of powered monitors and as such expects a speaker level in (possibly two if there are stereo lines). We use it for keys as the keyboard has no other self monitor. The keyboard is floating wrt ground as it is powered by a wallwart. The kb players has a box I built that allows level setting of keyboard and monitor mix without touching the actual keyboard levels so the FOH gets an unchanging kb level. The other powered "monitor" is actually a Roland keyboard monitor (KC-60) on a tilt stand used by the band leader. It actually works very well for this purpose and has great sound. It was bought used ($75 it says on the back... I have it home to repair the ground on the cord :P ) and one of the three chanels has issues. I am just noticing that it does have a ballanced mic level input, so I could use a standard DI for isolation in future if I need to. I am not afraid to spend money, but I would like to put it to the best use as it is limited. Fixed grounding comes before new equipment in my book. It looks like this will happen. There have been two very large breaker pannels installed already and there are many inspections to go through ahead. I am going to set up a plan for power, signal and data for audio. I will do a second for stage lighting as well, if for no other reason than keeping the audio power from being used for lights :) If I need more than one breaker for audio power, I will make sure it is on the same phase. -- Len Ovens www.ovenwerks.net

These articles may be of interest. http://www.rane.com/note151.html http://www.rane.com/note110.html I have worked at the same venue for many years and have noticed more frequent problems recently with hum and buzz with some bands' equipment while most are perfectly fine. I suspect changes in the grounding such as corroded ground rod connectors or dryness in the soil they are in. The boss is investigating. I always try to run all PA and band equipment from the same circuit if capacity is sufficient. The previously mentioned 750 foot run may be a problem though with probable significant voltage drop. Cheers Roger

On 02/10/2015 05:43 PM, Len Ovens wrote: DI boxes are designed to connect an unbalanced output to a balanced input. I've also pondered running DI boxes "backwards". From a technical view, I'd need to study the schematics of the driving equipment, the DI box, and the driven equipment to convince myself that it could work and not damage anything. I might try calling technical support. From a execution view, I'd need the right adapter cables (such as XLR-F to XLR-F). But from a conservative/ safety view, I'd rather hook everything up the way the equipment manufacturers tell me to and not have to worry about it. I'd look in the monitor manual and follow the manufacturer's instructions. If you don't have a manual and can't get direction from the manufacturer, I'd use an isolation transformer with suitable connectors and cables. That looks useful. If the mixer has balanced outputs, the stage amplifiers have balanced inputs, and both are powered from the same supply, isolation transformers should not be necessary. I'd run balanced cables from the mixer to the amps and call it good. That said, good isolation transformers will cause a small lose of signal and fidelity, but they might provide protection for certain equipment failures or operator errors. It is best to keep balanced signals in balanced cables for as far as practical. I wouldn't plug a TS cable into an balanced TRS output. First, you are shorting one half of the balanced driver output circuit. Second, you are injecting chassis ground noise into the audio circuits. I assume the DVD and computer are unbalanced. If those are next to the mixer, cables alone might do. Check your mixer manual. If the runs aren't local and/or you can't find an authoritative wiring diagram, I'd use DI boxes. David

On 02/15/2015 04:50 PM, Roger wrote: Those are good documents -- I finally finished reading through them last night. Some output driver circuits/ chips can handle shorting the signal negative pin to the signal ground pin. Others cannot. If you are certain your sending equipment can do this, then a custom cable might work. If you're sending equipment cannot handle this, or if you are not certain, then you either need an isolation transformer or a suitable balanced-to-unbalanced converter circuit. David

On Wed, 11 Feb 2015, Fons Adriaensen wrote: Right, I found one. It also has three styles of connector (XLR/TRS/RCA) so cabling will be easier. They are available from a local store too which is another plus. I will order the boxes (I think 6 lines worth will cover anything possible with the mixer we have). I was going to put in a network cable anyway (if we use it right now or not) but could aslo put in optic line(s). Are they subject to degradation with time if not in use? It is not a long run at less than 100ft (this includes running it up above the ceiling and dodging open rooms etc. The dx from stage to mix is less than 50ft.) -- Len Ovens www.ovenwerks.net

On Thu, 12 Feb 2015, David Christensen wrote: No, not at all. I don't think it is worth it for us at this point. I am ordering 6 channels of one to one isolation to give isolation for up to 4 monitors and two mains (all mixer outputs to stage). I will put digital lines (wiring, but no switches or other end points) in during reno so that in the future we can change things if we like. There are other things network can be used for besides audio as well. But our audio will stay analog probably at least as long as this new mixer we just installed last year. It is already amazing what new options are available since I picked up the mixer. I am hoping it will be good for another ten, but even five years from now, digital could be cheaper than analog... CAT5 could no longer used for that matter. -- Len Ovens www.ovenwerks.net

On Mon, Feb 16, 2015 at 12:04:35PM +1100, Roger wrote: Digital snakes are cost-effective only if connected directly to a digital mixer which then doesn't need AD converters, mic preamps, and DA converters (apart for connecting analog gear locally). As is the case with Digico. Ciao, -- FA A world of exhaustive, reliable metadata would be an utopia. It's also a pipe-dream, founded on self-delusion, nerd hubris and hysterically inflated market opportunities. (Cory Doctorow)

On 02/12/2015 11:13 PM, Ralf Mardorf wrote: Muletape is my favorite: http://www.neptco.com/website/neptco.nsf/sec/6.3 David

On Fri, 13 Feb 2015 13:35:23 -0800 (PST) Len Ovens <len(a)ovenwerks.net> wrote: If pulling through (especially) conduit or trunking, then if at all possible pull all the cables together, otherwise you run the risk of new ones rubbing through old ones with 'interesting' consequences. Also, don't forget to pull a new cord through as well - the next guy may be you! -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song.

On Fri, 13 Feb 2015 14:05:21 -0800, jim wrote: Len: I used (and still would use) conduits behind gyprock too and I avoided turns. You likely can't chose to use surface-mounted cable channels (of the kind that can be opened) on the walls, but perhaps the building has got a suspended ceiling. Even if it doesn't has got a suspended ceiling, under a "normal" ceiling you could use cable channels that can be opened, assumed the room is high enough. OTOH those cable channels might look ugly. However, behind gyprock walls and between the a ceiling and a suspended ceiling, I used and still would use some kind of tube too.

On 02/09/2015 11:38 PM, Roger wrote: Thanks. There are electrical contractors that specialize in testing/ commissioning electrical systems. You might want to find one. I researched that in the past, and seem to recall that good quality balanced equipment (e.g. with good driver chips) and good quality XLR cables can send a signal ~900 feet before the high end starts to roll off. David

It seems even with all power coming from one outlet, I have one amplifier with some hum. It is way less and by playing with levels I was able to make it so low as to not be noticed. However my plan of isolating everything should fix it completely. -- Len Ovens www.ovenwerks.net

On Mon, 16 Feb 2015, Roger wrote: Over 100 ft of unbalanced input. The hum was not there with the power ground lifted (now fixed). I will be Changing things so I have balanced out of the mixer -> through snake -> one to one isolation transformer -> unbalanced to amp. My final setup will be: all stage powered instruments or unbalanced sources will have a DI (transformer with ground lift), All returns to stage will have isolation transformers. Mics go straight. Anyway the hum was low enough that I had to tell people it was there, so I am at "good enough". I do have two pots at max and one very low to get it to work that way though. I will see what my isolation box does. -- Len Ovens www.ovenwerks.net

On Mon, 9 Feb 2015, David Christensen wrote: Yes. That is why I am starting now. That will happen anyway, but I would agree. I will not be running the wire or doing the install. But I do have input. That is why I need to think about it now. I expect our stage lighting will be minimal, but it does need some thought. There is also a coffee bar/kitchen close by to think about. -- Len Ovens www.ovenwerks.net