Number6 Posted August 1, 2015 Share Posted August 1, 2015 [quote name='Slipperydick' timestamp='1438444019' post='2834578'] Errm - No ! [/quote] In my experience as an electrical engineer and having studied Electro Magnetic Compatability (EMC) i would say yes. 😉 Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted August 2, 2015 Share Posted August 2, 2015 [quote name='Number6' timestamp='1438468258' post='2834791'] In my experience as an electrical engineer and having studied Electro Magnetic Compatability (EMC) i would say yes. [/quote] Not wanting to get into a pissing contest, in my 45 years experience as an electronics engineer. and having hands on experience of actually solving hum and RFi problems in the field, in various envoronments - although not specifically made a study of EMC. Quite often in practice, the cure makes no sense in theory, Question is, is it really an improved earth ? Always better to find the source if possible, I'm not convinced that its something in the house, But after eliminating the things I already mentioned, I'd try putting the earth rod backin place. I'm not a sparks, and I dont know about 17th edition regs, but a quick google suggests an additional earth rod connected via 10mm cable conforms. And would possibly be the most cost effective cure. Quote Link to comment Share on other sites More sharing options...
chris_b Posted August 2, 2015 Share Posted August 2, 2015 So everything was OK, you had work done on the house and now everything is not OK. The last change is always the point where you start the investigation. I'd get an independent earth/bond check done. Fix the problem not the symptoms. Quote Link to comment Share on other sites More sharing options...
Number6 Posted August 2, 2015 Share Posted August 2, 2015 [quote name='Slipperydick' timestamp='1438474494' post='2834823'] Not wanting to get into a pissing contest, in my 45 years experience as an electronics engineer. and having hands on experience of actually solving hum and RFi problems in the field, in various envoronments - although not specifically made a study of EMC. Quite often in practice, the cure makes no sense in theory, Question is, is it really an improved earth ? Always better to find the source if possible, I'm not convinced that its something in the house, But after eliminating the things I already mentioned, I'd try putting the earth rod backin place. I'm not a sparks, and I dont know about 17th edition regs, but a quick google suggests an additional earth rod connected via 10mm cable conforms. And would possibly be the most cost effective cure. [/quote] A TT system where the consumer provides their own main earth rod or the old system didn't appear to pick up any noise. The new system (this is an assumption) is TN-C-S or PME from a connection to the earthed neutral at the electrical intake. From what i've read above when the main earth is disconnected (be careful doing that by the way as there may be some earth leakage / fault currents) the noise disappears. So the old system was a stand alone earth that was fairly quiet the new system is a combined earth (from the supplier) and it is noisy but the noise disappears when the main earth is removed. So therefore i suggest the noise is being picked up by parallel paths somewhere on the PME supply system. Also installing another earth rod may not be advisable as spacing of rods can affect the earth loop impedance and also fault surface voltages can be introduced if the earthing isn't correct. Anyway those are my thoughts on the subject. For earthing definitely consult an electrician. Quote Link to comment Share on other sites More sharing options...
Leonard Smalls Posted August 2, 2015 Share Posted August 2, 2015 [quote name='Slipperydick' timestamp='1438466575' post='2834777'] Is there anything in current regs to say you cant keep the earth rod or fit a new one in the same place, and have PME es well ? Might be a good compromise and wouldnt cost the earth. Much better to find the source and eliminate/ supress it it that to try and supress the amp though isnt it ? [/quote] There's nowt that says you can't have an earth rod and a PME. However, the house earth would still be at 0V effectively with respect to neutral becausae of the PME system. There's also the added possibility that if there's a supply neutral fault all your neighbour's ground paths would be through your earth rod... If the fault is caused by RFI, the old earth may have been of high enough resistance to actually be at a higher voltage with respect to neutral, and so mask any lower rfi voltages. However, a lower earth loop impedance means higher prospective fault cuurents - a good thing as it means RCDs, MCBs and fuses operate faster. If RFI is the problem, a decent filter such as the F3 Micro (http://www.evoaudio.uk/wychwood.htm) would sort it. But as RFI is quite a large problem on mains I don't understand why manufacturers don't put effective filtration in the power supplies of amplifiers... Quote Link to comment Share on other sites More sharing options...
dmccombe7 Posted August 2, 2015 Share Posted August 2, 2015 My Jazz bass gives a buzzing with modern Hi-Fi style amps whereas the older style amps are fine. I've always put it down to the top end clarity of speakers and amps these days. Using my Ampeg SVT 4 i don't get it with my Berg cabs. Its obviously worse when i face the amp. My active basses don't have this issue. Only my Jazz when bass set ful on vol and tone control. You could try cutting your high end a bit or reducing GAIN and increasing master volume which might help. Dave Quote Link to comment Share on other sites More sharing options...
HowieBass Posted August 2, 2015 Share Posted August 2, 2015 The OP seems to be hearing this noise only recently which suggests it's connected to a change in the house electrics, not a consequence of their choice of instrument or amp... as others have suggested it's probably worth trying to tackle the problem at source. I'm just wondering what I'll find when I move to my 'new' house in a few weeks time as it seems noisy electrical installations are quite capable of passing all safety regs. Quote Link to comment Share on other sites More sharing options...
Number6 Posted August 2, 2015 Share Posted August 2, 2015 [quote name='Leonard Smalls' timestamp='1438501574' post='2834874'] There's nowt that says you can't have an earth rod and a PME. However, the house earth would still be at 0V effectively with respect to neutral becausae of the PME system. There's also the added possibility that if there's a supply neutral fault all your neighbour's ground paths would be through your earth rod... If the fault is caused by RFI, the old earth may have been of high enough resistance to actually be at a higher voltage with respect to neutral, and so mask any lower rfi voltages. However, a lower earth loop impedance means higher prospective fault cuurents - a good thing as it means RCDs, MCBs and fuses operate faster. If RFI is the problem, a decent filter such as the F3 Micro (http://www.evoaudio.uk/wychwood.htm) would sort it. But as RFI is quite a large problem on mains I don't understand why manufacturers don't put effective filtration in the power supplies of amplifiers... [/quote] Exactly.....you don't want to introduce earth fault paths onto a stand alone earth spike. And ferrite beads / filters can work well on suppressing interference but you may have to experiment where to install them. Quote Link to comment Share on other sites More sharing options...
Number6 Posted August 2, 2015 Share Posted August 2, 2015 (edited) Also worth doing a bit of research on Electro Magnetic Compatability (emc) as there are lots of sources of noise making radio interference out there. Edited August 2, 2015 by Number6 Quote Link to comment Share on other sites More sharing options...
Norris Posted August 2, 2015 Share Posted August 2, 2015 [quote name='chris_b' timestamp='1438475164' post='2834826'] So everything was OK, you had work done on the house and now everything is not OK. The last change is always the point where you start the investigation. I'd get an independent earth/bond check done. Fix the problem not the symptoms. [/quote] This ^ Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted August 2, 2015 Share Posted August 2, 2015 A wire earthed at one end is an aerial. Earthed at the substation, the earth cable will be in effect an aerial, so anything thats radiating and connected to it will introduce hum into the house. also using an SCR, such as lam dimmers seem to introduce a lot of noise which can sometimes even be seen on the mains waveform using a scope. I would be interested to see what happens if the OP temporarily disconnected the earth from the amp. Quote Link to comment Share on other sites More sharing options...
TimR Posted August 2, 2015 Share Posted August 2, 2015 He did that and the noise went away. The worry is that they've taken the earth spike away and his mains are now earthed through the spikes in the other houses. Which sounds to me is exactly what has happened. Quote Link to comment Share on other sites More sharing options...
dmccombe7 Posted August 2, 2015 Share Posted August 2, 2015 The explanation of sensitivity of new house electrics is higher than the older ground spike seems to make more sense. I remember years ago being told that you should only earth one amp in the loop when using PA systems to reduce earthing loops. Not sure whether it was genuine or not tho. Dave Quote Link to comment Share on other sites More sharing options...
TimR Posted August 2, 2015 Share Posted August 2, 2015 [quote name='dmccombe7' timestamp='1438521456' post='2835115'] The explanation of sensitivity of new house electrics is higher than the older ground spike seems to make more sense. I remember years ago being told that you should only earth one amp in the loop when using PA systems to reduce earthing loops. Not sure whether it was genuine or not tho. Dave [/quote] That's a completely different situation. That's gross loop hum. When a loop is created through the building's mains into an amp, through the instrument lead, then into the mixer/keyboard and back into the building via the mixer/keyboard power lead. In that case the loop needs to be broken at the instrument cable using a ground lift device. In this case noise is being injected from the building's earth somehow. Or there is airborne noise that is somehow not being drained down to a proper earth. Quote Link to comment Share on other sites More sharing options...
Leonard Smalls Posted August 2, 2015 Share Posted August 2, 2015 [quote name='TimR' timestamp='1438521173' post='2835108'] The worry is that they've taken the earth spike away and his mains are now earthed through the spikes in the other houses. Which sounds to me is exactly what has happened. [/quote] A PME has a maximum earth loop impedance at the house main earth terminal of 0.35ohms. Which is why, from a safety point of view it's the preffered option - RCDs are guaranteed to work quickly (i.e. 15 or so milliseconds on average). If a sparky removes a TT earth (i.e. a spike) and replaces it with a TNCS (i.e. earth connected to supply neutral) they have to clear it with the power distribution company first who'll determine if this system is suitable - i.e. if there's sufficient multiple earths between supply transformer and house to be supplied (the supply neutral is earthed at a number of points, not just through the centre tap of the supply transformer). If they say OK then the sparky will measure the earth loop impedance where it enters the house (this is Ze) and at every outlet within the house (these are called Zs). The certificate he issues will have all these values recorded on them. So if there's no supply earth there's not likely to be a Ze value of less than 0.35... Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted August 2, 2015 Share Posted August 2, 2015 [quote name='TimR' timestamp='1438521173' post='2835108'] He did that and the noise went away. The worry is that they've taken the earth spike away and his mains are now earthed through the spikes in the other houses. Which sounds to me is exactly what has happened. [/quote] I was under the impression that he had disconnected the earth from the consumer unit temporarily. I'd try putting a spike back if it was me. Unless theres anything in wiring regs to say he cant have a supplementary earth. I know there will be a different potential between the two, but it wont necessarily create any problems will it. Quote Link to comment Share on other sites More sharing options...
dmccombe7 Posted August 2, 2015 Share Posted August 2, 2015 Yep that more or less what was explained to me many yrs ago. Because the earth point has been changed could the OP be picking up mains harmonics usually associated with frequencies higher than 150Hz. Recently experienced this on some HV systems at work altho they were coming from a 250KV supply it causes interference and eventual damage from 230V / 110V down to 24V systems across various electronic systems. Usually capacitors or thyristors failing. This could only be picked up with special frequency monitoring equipment. This was caused by local steelworks mains filtering system having been by-passed when it had issues. It might be that the audio system is highlighting this kind of thing now that the earthing has been changed to mains earth rather than local spike. ? Dave. Quote Link to comment Share on other sites More sharing options...
spongebob Posted August 2, 2015 Author Share Posted August 2, 2015 Thanks for all the excellent replies on this - far exceeded my expectations! Got the Behringer box coming tomorrow - so I'll let you know if it does the trick.... Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted August 2, 2015 Share Posted August 2, 2015 (edited) [quote name='dmccombe7' timestamp='1438523615' post='2835128'] Yep that more or less what was explained to me many yrs ago. Because the earth point has been changed could the OP be picking up mains harmonics usually associated with frequencies higher than 150Hz. Recently experienced this on some HV systems at work altho they were coming from a 250KV supply it causes interference and eventual damage from 230V / 110V down to 24V systems across various electronic systems. Usually capacitors or thyristors failing. This could only be picked up with special frequency monitoring equipment. This was caused by local steelworks mains filtering system having been by-passed when it had issues. It might be that the audio system is highlighting this kind of thing now that the earthing has been changed to mains earth rather than local spike. ? Dave. [/quote] Thyristors cause all sorts of weird things to happen. In the early 70s 75%of british made TVs had similar thyristor PSUs, and all the same 200V output, so all triggering at the about same point on the mains waveform. Imagine the effect on the mains in tower blocks... Edited August 2, 2015 by Slipperydick Quote Link to comment Share on other sites More sharing options...
dmccombe7 Posted August 2, 2015 Share Posted August 2, 2015 No wonder electronics were so unreliable back then. I used to stay in tower block in 70's. Dave Quote Link to comment Share on other sites More sharing options...
spongebob Posted August 3, 2015 Author Share Posted August 3, 2015 Got the Behringer box - and it doesn't make any difference whatsoever! It's definitely an earthing issue, just need a modern way to solve it..... Quote Link to comment Share on other sites More sharing options...
TimR Posted August 3, 2015 Share Posted August 3, 2015 (edited) When you touch any metal parts of your amp does the buzzing go away? What kind of buzzing is it? Is it 50hz hum or something else. Have you turned absolutely everything else off and unplugged it. Fridge/freezer, central heating/water pump? Is it there 24/7 or could it be related to a dodgy outside halogen spotlight nearby? Which earth did you disconnect? Edited August 3, 2015 by TimR Quote Link to comment Share on other sites More sharing options...
Slipperydick Posted August 3, 2015 Share Posted August 3, 2015 [quote name='spongebob' timestamp='1438619823' post='2835822'] Got the Behringer box - and it doesn't make any difference whatsoever! It's definitely an earthing issue, just need a modern way to solve it..... [/quote] If you lightly stroke a metal part of the amp, or your Bass with it powered up do you feel any tingling ? Could you temporarily connect it to the mains using a four way lead, but with the plug upside down, as in the photo, and let us know if it makes any difference ? You will be removing the earth and also reversing the polarity. [attachment=197812:20150803_235517.jpg] Quote Link to comment Share on other sites More sharing options...
TimR Posted August 4, 2015 Share Posted August 4, 2015 That is a seriously dangerous suggestion. Do not do that! Quote Link to comment Share on other sites More sharing options...
Norris Posted August 4, 2015 Share Posted August 4, 2015 Oh my goodness. That photo made me cringe. Please stop fannying about and get back in touch with your sparky Quote Link to comment Share on other sites More sharing options...
.thumb.jpeg.795def0f48febb3d6ebc9016d16df248.jpeg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.