Members wesg Posted October 11, 2015 Members Share Posted October 11, 2015 Hey, all -- Just trying to understand some issues I've had recently and whether or not buying expensive power bars might fix them. I currently use 1U APC power bars in my racks, which feed the other gear. I forget the model number, I originally bought them for datacenter use many years ago and they cost about $150 each. No fancy features. This is for a five-piece bar band with generally decent equipment. Venue S --Guitar, through Marshal transtube amp - had a strange problem the other night. A buzz through the amp no matter what we tried, including trying different outlets in the room. It was the strangest thing, if the guitar player turned at a certain angle, the buzz was decreased. Changing to/from single-coil pickups did nothing. Neither did touching/not-touching the strings. I believe this venue may have overloaded circuits, based on the behaviour of the "building wiring fault" light on my power bars. They will turn on as the equipment is powered up, suggesting that there is approximately 5V difference between neutral and ground. I am reticent to stick multimeter probes in anything at the venue when people are watching. I already had to deliver the bad news that one-half of their house system is dead. Stage power is provided via a contractor-grade extension cord. Venue U --Piano (Yamaha CP4). When sending stereo unbalanced to the (X32 rack) board, I got a loud thump about 0.25s after playing a note. Changing to balanced mono fixed this. Did not try stereo balanced. Bass - bass amp (Mark Bass, Little Mark II?) - amp hummed until the "ground lift" was engaged. Output was plugged into X32. Are these the types of issues that typically come from "bad power"? How do you guys characterize "bad power"? If the venue has cheap house light dimmers, does turning them on full blast generally eliminate the PWM Triac noise? What exactly do those Furman power bars do? Do they have great big L-C 60Hz bandpass filters or something? I don't know exactly what my APC units have, but I suspect they have basic ingress EMI/RFI filters and MOVs for surge supression. Thanks,Wes Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 11, 2015 Members Share Posted October 11, 2015 I'll offer there's three different types/kinds of "bad power", being: 1) Defective.2) Overloaded.3) High EMI situations. My experience of seemingly common defects (#1) more-or-less in order of frequency: 1) Broken or worn-out outlets.2) Bootleg or open grounds.3) Swapped neutral and load.4) Swapped neutral, load, and ground.5) Open neutral.6) Worn-out breakers.7) Incorrect voltage and type for the outlet. I always meter before plugging in, I don't care who's watching. Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 12, 2015 Members Share Posted October 12, 2015 Can be any and all of the above, plus connection of neutral to ground connection other than at the main service entrance bond point. The guitar problem could be induced noise into the pickups or wiring. Generally, power "conditioners" do not solve any of these problems but may in fact make them worse. Link to comment Share on other sites More sharing options...
Members onelife Posted October 12, 2015 Members Share Posted October 12, 2015 ... The guitar problem could be induced noise into the pickups or wiring. ... With electric guitar situations, it's important to discern if the noise originates with the guitar or the amplifier. I usually test with a)guitar plugged in and turned up as in performance situation, b) guitar plugged in and turned down to test for noise being induced in the pickups and c) the amplifier on its own. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 12, 2015 CMS Author Share Posted October 12, 2015 I am reticent to stick multimeter probes in anything at the venue when people are watching. Why? It's your gear. What exactly do those Furman power bars do? Do they have great big L-C 60Hz bandpass filters or something? I don't know exactly what my APC units have' date=' but I suspect they have basic ingress EMI/RFI filters and MOVs for surge suppression.[/quote'] The 1U units have the same thing your APC's have...the components you mention here. Minimal protection and filtering. As you're experiencing...it doesn't do much, if anything, except drain your wallet. Mark described the various issues that can cause problems. We could add that some of our gear can make the problems worse, but for now, the power the topic and should be addressed. The trouble here is that most of this if not all, would require the services of an electrician, and someone to pay him/her. Link to comment Share on other sites More sharing options...
Members wesg Posted October 12, 2015 Author Members Share Posted October 12, 2015 Thanks for the feedback, guys. There is certainly a lot to learn in this business if you want to manage trouble-free shows. I remembered something else about venue S - the second-last time we played there, second guitar had trouble with his Line 6 cordless thing buzzing. That time, we just eliminated the cordless unit to get going. But this time it was fine and the lead guitar player - with a corded unit - was having troubles. *frustrating* - I need to get my load-in faster so that I can spend time troubleshooting this stuff better when it happens. We're working on become more efficient, but it still took us nearly two hours to unload and setup on Friday. I'm the biggest problem, on top of PA I bring an organ, a Leslie, and two keyboards to the gig. Add troubleshooting the venue's PA and coordinating with the opener, and we ran out of time to test the guitars until changeover. I'm glad consensus here seems to be that I'm not setting myself up for failure by not buying Furman power bars. I've been questioned on this in the past, and my response is always, "What do the Furman units do that mine don't?"...the answer is, invariably, something along the lines of "they make your power more gooder". None of the gear in the band is particularly old or low-quality, with the exception of the organ and Leslie which I believe are fine (and were off when we were having trouble). Mark, thanks for enumerating that list of stuff to consider. I did have to hunt for outlets that weren't broken at the bottom the other night. Will ANY equipment work with an open neutral? I would think that any equipment doing this would violate every code in the book (building ground loop!). Onelife, thanks for the guitar troubleshooting suggestions. I'll run down that list if this happens again. Craig - you've hit the nail on the head! I don't need to stick meter probes into the venue's wall. I can use the convenience outlet on my powerbars for that! I'd also like to fire up a scope and look for weird harmonics or dimmer noise, but I think that might be pushing it a bit. What do you guys do when you find an actual wiring fault in the premises wiring? I know at Andy's level, he probably says, "F-U you idiots, get an electrician in here NOW" but that's not in the cards for a bar band. I have considered making up adapters for things like flipped hot/neutral conductors, but the potential liability and lack of appropriate training make me reticent to do so. Wes Link to comment Share on other sites More sharing options...
Members onelife Posted October 12, 2015 Members Share Posted October 12, 2015 . . . Will ANY equipment work with an open neutral? I would think that any equipment doing this would violate every code in the book (building ground loop!)... When I first moved into my house I was experiencing some weird power issues. One problem was excessive "strat buzz" (EMI being picked up by single coil pickups) and another was arcing in some electrical outlets that occasionally had high current devices like heaters plugged in. After experiencing some brownouts, I called the power company and they found a faulty neutral connection right at the transformer. After they replaced a short wire on the pole everything worked much better. The problem with an open neutral is that some things appear to work. I mentioned my experience to a friend of mine who used to be an electrician for the power company. I will have to check with him again but, IIRC, he mentioned measuring 147 Volts from the hot to ground as an indication of a faulty neutral. Another interesting point is that when I replaced the sockets where the arcing had taken place, it was the neutral connection that was scarred. Link to comment Share on other sites More sharing options...
Members dboomer Posted October 12, 2015 Members Share Posted October 12, 2015 Your are probably making it more difficult that it really is. Improper power and dangerous power are something that a professional needs to deal with (and soon). But in my experience a lot of problems get mistakenly blamed on bad power. Before you you go looking for an exotic problem you need to rule out RF-borne interference, pin 1 problems and ground differentials caused by equipment common grounds getting referenced to different ground potentials (not plugging everything into the same AC strip). I think you'll find these three things responsible for 99.9% of typical "bad power" problems. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 13, 2015 CMS Author Share Posted October 13, 2015 I think another general issue is the oft-asked questions, "Is this power conditioner box worth the money? Will it help?" Far too often the answer is "no", on both accounts. The protection is mediocre and one-shot..when the MOV takes a hit, it sacrifices itself. The filtering, as Don states, is far more often NOT something that any power conditioner can deal with, because it's not in the power line at the point of this device. I view these units as convenient power strips. The lights are useful sometimes. The power switch might be helpful. But I don't even give the "conditioning" a second thought. It's like having leather seats in a work truck. Nice to know they're there, but not too useful to the truck's daily work. Link to comment Share on other sites More sharing options...
Members Pro Sound Guy Posted October 13, 2015 Members Share Posted October 13, 2015 Surge suppressors are useless for your issue Think isolation transformer with filters Think voltage regulation http://furmansound.com/product.php?div=01&id=P-1800AR Think about spending a couple bucks and get one of these http://www.3starinc.com/ac_power_tester.html Link to comment Share on other sites More sharing options...
Members boomerweps Posted October 13, 2015 Members Share Posted October 13, 2015 Before you you go looking for an exotic problem you need to rule out RF-borne interference' date=' pin 1 problems and ground differentials caused by equipment common grounds getting referenced to different ground potentials (not plugging everything into the same AC strip). I think you'll find these three things responsible for 99.9% of typical "bad power" problems.[/quote'] Concur with Don. So much that I found dual circuit supplied power strips that had each circuit supply 4 outlets each while the grounds were interconnected between the 2 groups of 4 outlets. I doubled up two of these units & used two proven good power outlets to supply them. Then I connected the whole PA and back line to those power strips. All power issues were solved with that at all the venues the band worked after that. Granted these power strips were originally configured with 20 amp plugs. I down rated them with 15 amp standard Edison's. They also came with 15 foot power cables. I shortened the one to 3 foot for plugging into the first unit. I had three of these units but a buddy of mine wanted one bad after he saw and heard the results of having a common ground. I swear by it. Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 13, 2015 Members Share Posted October 13, 2015 What do you guys do when you find an actual wiring fault in the premises wiring? I generally put a piece of board tape over the outlet, and move on. If I haven't fronted the venue, and checked out the power situation ahead of time, I bring "a few hundred feet" of "extra" 12ga. extension cable. I'm aware of outlets at local venues that have been sporting my untouched board tape for decades... some going on 4 decades. Oh, and I'll mention: I own "quite a bit" of 12-3 extension cables... probably "a few thousand feet"... way more than I need. The reason I have purchased so much is from times in the past when I thought throwing in "a couple hundred feet" extra extension cable "should be plenty" (because I was assured "there's plenty of power at the stage... bands play here all the time.")... and it wasn't, and I was way too far from my shop to go get more in a timely manner. Link to comment Share on other sites More sharing options...
Members wesg Posted October 13, 2015 Author Members Share Posted October 13, 2015 Interesting advice here. Keep it coming! I'm glad to read that I'm not the only one suspicious of the "oh it's bad power" conclusion that bands reach when things don't work right. I've made attempts a "star ground" layout at times, simply because I know it is good practice when building amplifiers, but there are always seems to be something that breaks the star. Either the bass amp, or the house power amps, something like that. I should probably make a better effort at this, and get some better data on my loads. 15A circuits with NEMA 5-15R receptacles are the norm in Canada. Thank God for solid-state Class D amplifiers! The "pin 1" question is interesting. I read the notes at Rane.com several years ago, have thumbed through Rod Elliot's site, and I have to admit, I'm still confused. I know that having both pin 1s connected to the shell is bad (ground loop); I had some cables like this and clipped one end. But I don't know if I should have both ends clipped, or which end is "better" to have grounded to the shell. I think most of my commercial cables have neither end connected. I should check. boomerweps talks about shortening power bar cords....this is probably a good idea. I usually have 10 or 12 feet wrapped up at each rack! They used 12 or 14awg copper, so they could be made into extension cords. Speaking of extension cords, I normally bring a 50 footer and two 15 footers, rated for 12 and 14A respectively IIRC. Outdoor gigs, I will also bring a monster 50 footer than is rated for 15A and is big around as a garden hose. This has proved adequate for me ... so far ... but if I ever get a meaningful light show, I will certainly need more. PSG - do you know if that Furman unit does power regulation via boost/buck conversion, or is it one of those multi-tap transformer dealies? Do you have any idea if the noise attenuation is anything fancier than a small cap and a choke at the ingress? I find their product descriptions difficult to penetrate. Re the power tested you mentioned...I bought one...was going to use it last show, but couldn't find it. Argh! Maybe I should leave it plugged into one of my rack PDUs. Mark - great stage-tape advice. That reminds me, I saw a band curse and rip tape off the wall at venue S a couple of years ago. I bet there is a "Mark" running around my town taping outlets... I can't wait for my show next month, I'm already anticipating power problems. I got a non-trivial shock last spring from touching the railing while holding a patch cord plugged into non-defective equipment. I guess my strategy should be to find a stage power box that tests good, whose ground is within a few V of the railing, and whose neutral is pretty close to ground. Then run everything on stage through that box. Wes Link to comment Share on other sites More sharing options...
Members dboomer Posted October 14, 2015 Members Share Posted October 14, 2015 In speaking of pin1 problems I'm not talking about the cables. Cables should not have the ground connected to the shell per AESspecs period. That said most Asian built cables do as standard practice. Go through your cables and cut this connection of you have it in any of them. Now once your cables meet ARSstandards you can get into real pin one problems. The he pin one problems that I'm speaking of are that some gear balanced or otherwise, will not correctly connect with other XLR 3 pin gear if you leave pin one connected. This is caused by a flaw in the design. Believe it or not, even within some brands their own equipment will not plug into some of their other equipment ... But I'm not naming names everyone should carry a few pin 1 lift adapter/cables as you might run into this problem from time to time. Link to comment Share on other sites More sharing options...
Members wesg Posted October 14, 2015 Author Members Share Posted October 14, 2015 Thanks for the cable advice, Don - I will take both of those suggestions. I have been meaning to go through all of my Asian-made cables anyhow. I discovered that some of them had too much insulation stripped going to pins 2 and 3, this caused a short in one that got twisted. "real pin 1 problems" - this is kind of interesting. I've always wondered why the heck ground lift etc was even relevant. Why in God's name would you want your chassis ground involved in the audio path? My main experience with balanced signalling is telephone, ethernet, and differential SCSI where balanced signals exist without any ground reference; the ground connectors only being used to connect the equipment chassis together for RF shielding ... when shielding is even necessary! Now that makes me wonder about the XLRs I had with the shield connected to pin 1. They came from my dad's radio shack. I wonder if he cared more about RFI than ground currents...I noticed that some of his other cables were "unbalanced XLR", he would have had zero CMRR on those. Link to comment Share on other sites More sharing options...
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