|
|
Post by pinkie on Apr 27, 2017 6:38:08 GMT
My mains voltage has varied wildly between a high of 252V and a low of 235V. Both of those are comfortably within permitted limits. It can go down to about 220v before it is out of the range equipment is supposed to be designed for |
|
|
|
Post by pinkie on Apr 27, 2017 6:48:01 GMT
Hi Jules - since I've had the AN Oto, I've simply tried a cheap eBay and more expensive MCRU DC mains filter, both without any improvement. I've considered all manner of possible fixes (BMU, regenration, dedicated spur/circuits/CU) hence my interest in this thread. Since I've been at my current address, my buzzing amp history is as follows: Quad 306 or Quad 406 - no buzzing, but Croft Micro 25 Basic pre buzzed Monarchy SM70pro - buzzing NVA A40 MKII monoblocks - no buzzing, but high frequency treble ringing, confirmed as local to me as RD tested same amps at NVA towers, in my presence, without the issues Audio Note P-Zero monoblocks - buzzing Restek MAMP monoblocks - buzzing AN Oto SE - buzzing @ Kevin - as has been highlighted by this thread alone, what might work for one doesn't always appear to work for another and that is why constructive discussion and debate (without the constant need to question technical/scientific points) is very much appreciated and valued. I've followed your experiences here and elsewhere with interest, in the hope that they'd offer hope to me. @ Richard - as outlined above, I have a history of buzzing amps. I also have a friend who is a electrician by trade and when I next see him, I'll be asking him to come around and check my DC offset. With regards voltage, when I had my ISOL-8 Sequence, I seem to remember that it would swing between early 230's to late 240's. First - to clarify a point, the ONLY time I have asked my friend for help regarding ANY forum matter was the safety issues related to Balanced Power (and an explanation of how it works, and grounding issues generally). He's not interested, and I know I am more than a bit cheeky getting him to help with matters directly relevant to me, like fixing and modifying Pips, without getting him involved in the troubles of forum beliefs. I did pick up a bit working with engineers in my time at PT. RMS voltage is GCSE physics GCSE physics - BBC. "All this going on about technical stuff and measurements" is how the competent engineers I know design equipment and troubleshoot problems like yours. They are completely successful. I would be confident if you took your amp to a competent engineer they would diagnose the problem, and if achievable fix it. There is a presumption that your problem is related to the mains - which on this forum, and this thread attracts enthusiastic "wet finger in the air" well-meaning suggestions (like Kevins) for fixes. Let me go out on a limb here. It's probably NOT the mains. Breakfast calls. I can suggest some reasons later, if you would like |
|
|
|
Post by John on Apr 27, 2017 6:53:09 GMT
This is working in Martin's system it may or not work in other Systems as mains very
Perhaps this is something Ps audio need to look into
But in the context of Martin's system seems a bargain
|
|
|
|
Post by pinkie on Apr 27, 2017 7:53:12 GMT
At this point (and forgive me if I've missed it), I would have a qualified electrician check your earth quality, as well as DC. A good earth is paramount to system performance. Really? The only earth at my house is a spike under the terrace and another in the garden. I can disconnect both at the same time - there is a bar for testing purposes - and they have no effect on system performance (Blue Peter warning - don't try this at home). The earth impedance here is about 40 ohms when connected Good GROUNDING is paramount to system performance. They are not the same. And I struggle to see how grounding (or earthing) issues would cause mechanical noise from a transformer. The good point this raises, and I forgot to ask Orbscure, is "are you sure this is mechanical transformer noise and not other hum causing the problem?" |
|
|
|
Post by MartinT on Apr 27, 2017 8:05:54 GMT
Jeez, Richard, don't you ever give up? I have had a qualified electrician visit me and talk about the different earthing strategies used in the UK. Bonding to neutral at points along the line (and the line taken to ground at those points) is becoming increasingly frequent, but it can still go wrong when entering the household. It's worth checking and should be a lot lower than 40 ohms. Poor earth at the system can lead to all manner of nasties, as Mike posted earlier. My advice stands: have a qualified electrician come and check it.
|
|
|
|
Post by pinkie on Apr 27, 2017 8:54:07 GMT
Jeez, Richard, don't you ever give up? I have had a qualified electrician visit me and talk about the different earthing strategies used in the UK. Bonding to neutral at points along the line (and the line taken to ground at those points) is becoming increasingly frequent, but it can still go wrong when entering the household. It's worth checking and should be a lot lower than 40 ohms. Poor earth at the system can lead to all manner of nasties, as Mike posted earlier. My advice stands: have a qualified electrician come and check it. i don't understand. Are you saying my HiFi doesn't sound the same with no connection to earth? How about systems on aeroplanes? Or that my earth impedance is not 40 ohms? (it varies with the weather) Or that in any house the impedance should be lower than 40 ohms, and "it should be a lot lower than 40 ohms"? Do you have any authority for that? Isntitute for electrical testing TT earth impedance must be below 200 ohms These folks, who maybe don't understand properly, think 200 ohms is acceptable - probably because that's what BS7671 says ( in France it has to be 100 ohms). Talking to a qualified electrician is not the same as understanding the technical and/or legal points. It never hurts (apart from financially) to have your earth tested - although a test of the household earth at the incoming supply, won't tell you anything about the earthing at each socket. |
|
|
|
Post by MartinT on Apr 27, 2017 13:19:30 GMT
Guys, this thread is about the MCRU Ultimate DC Blocker. By all means continue with the general discussion, but please start a new thread?
Thanks.
|
|
|
|
Post by orbscure on Apr 27, 2017 13:35:26 GMT
Guys, this thread is about the MCRU Ultimate DC Blocker. By all means continue with the general discussion, but please start a new thread? Is this not relevant thread drift Martin? If not, don't you or one of the mods not have the ability to move posts and start a new thread? 
|
|
|
|
Post by ChrisB on Apr 27, 2017 18:05:44 GMT
|
|
|
|
Post by ChrisB on Apr 27, 2017 18:50:20 GMT
While we're dealing with the housekeeping, can I remind everyone that the idea is to do battle with the knotty problem posed by the subject rather than the person who holds a differing view to your own.
Several guilty parties here.
Do it again and there will be canings. ......and I'll be checking to make sure you haven't put your physics text books down the back of your shorts!
|
|
|
|
Post by MartinT on Apr 27, 2017 18:53:04 GMT
It always used to be ham!
|
|
Barry
Rank: Trio
Posts: 195 
|
Post by Barry on Apr 28, 2017 2:02:53 GMT
The earth-neutral impedance will vary depending on which system is in use: TN-C, TN-S, or TN-CS. en.wikipedia.org/wiki/Earthing_systemMy mains supply uses the TN-S arrangement, for which the IEE limit is < 0.8 Ohm. In mine it is < 0.3 Ohm. If the system is the same as Martin's (TN-CS), the relevent figure is < 0.32 Ohm. Nowhere should the resistance be as much as 40 Ohms, let alone 200. I have also measured the DC offset on my mains supply: -18mV. Toroidal transformers are more prone to buzzing due to DC on the mains than bi-limboid designs, or those using E-I laminated cores. If the DC offset is ~ 100mV buzing can occur. However it depends on the rating of the transformer. DC offset is not a problem with toroidal taransformers of < 300VA rating owing to their high primary resistance. Toroidal transformers of rating > 500VA have a lower primary resistance so even a small offset of 100mV will set them buzzing. The mechanical noise is caused by the core momentarily saturating at the peak of each half cycle. When the core saturates, the inductance falls and the current rises and the primary impedance falls. In normal operation transformers are always on the verge of saturation. This is deliberate, if the transformer used more primary turns to more easily avoid saturation, it would have poor regulation because the primary resistance would be too high. So if you are going to use a toroidal transformer (even if it is in a BMU), fitting a DC block is a good idea. |
|
|
|
Post by pinkie on Apr 28, 2017 5:28:49 GMT
Barry
You forgot to mention the TT arrangement which is universal in France, and is the system at my house, and still used in the UK. Could you tell me what the current "regs"* recommended TT earth loop impedance is?
*BS7671
|
|
|
|
Post by MartinT on Apr 28, 2017 5:54:46 GMT
Thanks, Barry.
My house system is TN-CS and the earth impedance for my 100A radial circuit, with an RCD current of 63A, is 0.24 Ohms.
|
|
|
|
Post by pinkie on Apr 28, 2017 6:50:18 GMT
I think "les norms" in French may not be that enlightening for most readers French Entrees explanation is perhaps easier, "The earth conductor should be continuous throughout the installation and terminated at every lighting and power outlet point. It should be adequate to ensure an effective earth resistance of no more than 100 ohms maximum."
French Electrical Systems4th paragraph in the section "Earth / Bonding principles" BS7671 is "The regs" and I don't think the latest versions have changed the requirement from 200 ohms. NIC recommend 100 ohms. Of course, these systems are protected by a 500 ma "Disjoncteur"  We are on solid mountain rock. Anything under 100 ohms is fine  Of course, if your copper neutral line, is directly attached to your copper earth line 40 ohms would be a bit of a concern. |
|
Barry
Rank: Trio
Posts: 195
|
Post by Barry on Apr 28, 2017 10:53:49 GMT
Can't really answer that question pinkie. According to Wiki wiki.diyfaq.org.uk/index.php?title=Earthing_Types, a TT earthing system could have a Ze of anywhere between a few and several hundred Ohms. I think in the UK the maximum Ze for a TT earthing arrangement is <8 Ohms, but I could well be wrong. If you live on bare rock, the conductivity of the ground is going to be very low, which is why TT earthing systems must only be used with RCBs (residual current circuit breakers), which will trip within three half cycles if the difference between the current in the live and neutral conductors is >30mA. |
|
|
|
Post by MartinT on Apr 28, 2017 12:23:15 GMT
I've had to remove a couple of posts that were too close to ad hominem. Everyone: please address the post rather than the person.
Thank you.
|
|
|
|
Post by BilliumB on Apr 29, 2017 6:30:08 GMT
I'm on a TT system and have it checked regularly - from memory the 200 Ohm limit is I think correct. When last checked, mine was around 15 Ohm.
Cheers. Bill
|
|
|
|
Post by MartinT on Apr 29, 2017 8:47:17 GMT
Where do you live, Bill?
|
|
|
|
Post by BilliumB on Apr 29, 2017 17:59:04 GMT
Hi Martin
I live out in the sticks on a farm in North Devon. As mentioned I'm on a TT system which the electrician checks each year due to the business we run.
I've done quite a bit of investigation on hifi earthing options as I'm considering significant improvements to my earthing setup. (I'm plagued by high voltage and buzzing transformers which dc blockers and an isolation transformer have helped somewhat. The dc blocker I use consists of a board supplied to me by Nick Gorham who I expect designed / makes the MCRU unit under discussion.) Earth connection is currently just a single spike in a dry area under the eaves of the house - there is no connection between Earth and neutral within the property and so this opens up various 'improvement' options that should not affect safety (things are very different with a PME setup where the 'Earth' to the property is provided by the electricity distribution neutral line). Recent measurements have been between 15 and 20 Ohms depending on the weather. I seem to remember discussing the limit with the electrician and it being 200 Ohm max. A TT system due to this potentially high impedance has these days to be RCD protected of course.
Cheers. Bill
|
|
