Makes no difference in principle if both the tuner and amps are separate from the pre-amp. Unless you feel there is some magic length where balanced suddenly becomes essential?
Incidentally, I have an oddball capacitor mic made by Calrec which has some 100 ft of unbalanced cable twixt mic and power supply (and output) which works just fine under most circumstances. Not many domestic runs between pre-amp and amp would exceed 100 ft.
It is if you want to avoid hum loops. ;-)
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Dave Plowman dave@davenoise.co.uk London SW
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Not much point in using a balanced line if you're going to 'unbalance' it in this way. Use a transformer to do the job properly.
BTW, in most domestic equipment the mains and signal ground have a DC connection. Check with your DVM if you don't believe me.
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Dave Plowman dave@davenoise.co.uk London SW
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Could be - although I've not come across this in practice. Of course in the UK all domestic equipment must by law come fitted with our standard '13 amp' plug, and this is polarised so cannot be reversed.
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Dave Plowman dave@davenoise.co.uk London SW
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bang... bang... bang... bang... [sound of William Sommerwerck banging his head against a concrete wall] bang... bang... bang... bang...
Because not everyone with a Blu-ray player necessarily has an HD set with HDMI. By that reasoning, Blu-ray players should have only HDMI outputs. They don't. They have a variety of outputs, to support varying resolutions and "connectivity".
The component outputs on my Sony BDP-S550 DO NOT support 1080p.
They support 480p, 480i, 720p, 1080i. No higher. (See page 14.)
So to you all electronics add gain? Talk about two peoples separated by a common language.
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Dave Plowman dave@davenoise.co.uk London SW
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bang... bang... bang... bang... [repeated sounds of head banging against concrete wall]
Mr. Plowman, are you aware that you repeatedly change or twist the subject, without regard to what is actually being discussed? Because you do.
The "magic length" occurs when the power amp is far enough away to be on a separate circuit. Even if it's on the same circuit, there's no guarantee that the chassis grounds will be at the same potential. Which is, for me, The Fundamental Issue (with regard to ground loops.)
[More loud and anguished head-banging from yrs. truly.]
I "know people". I'm going to find someone who's a legitimate expert on audio grounding, and try to get some sort of definitive answer.
I've already given you chapter and verse which you choose not to understand. You could try re-reading it more carefully.
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Dave Plowman dave@davenoise.co.uk London SW
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Almost everything you've said goes against what I believe to be correct -- and some of it is unquestionably wrong. I have not had any "Aha!" moments of sudden clarity.
I've already asked two people for advice. I'm going to do some more research on this, and eventually get back to the group. Case closed, for the time being.
Please quote those parts. If I have given wrong information I'd like to know.
Have you checked your power amps with a DVM set to continuity to see if the mains ground is connected to the screen of the phono one? If not, why not? It's the crux of the matter...
Well, pretty well all of the advice you've been given suggests checking for *two* different DC paths - which are pretty easy to check for. Any interconnect path - audio, video, RF or mains. It's that simple.
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Dave Plowman dave@davenoise.co.uk London SW
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The Apollo 11 landing was almost aborted by such an issue.
The LM guidance computer was fielding all kinds of high priority data from the landing radar and control inputs. It was also, unbeknownst to the crew, also looking at the rendezvous radar as well. [This so an immediate Abort to Orbit could be accomplished; if the landing was abandoned.]
If the 2nd radar saw nothing, great, no data. BUT as it happens, it ran off a different phase of the LM power system, and the little big of noise between it and the landing radar was enough to be noticed. As a result, the computer started spitting out 1201 alarms, which was palnned for & acceptable, but disconcerting to everyone involved.
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Do you routinely have different phases running audio equipment in the same room in a house in the US? This smacks to me of bad practice and isn't allowed in the UK. Nor would it happen in a pro audio installation in say a TV etc studio - all the relevant equipment would be on the same phase - leaving the others for power hungry devices like air con and lighting.
Of course a power hungry large computer system might well be different - but the pitfalls of this are surely well known?
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Dave Plowman dave@davenoise.co.uk London SW
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No, but you can have 180 degree in phase situatuion between the split 240 transformer, and have 240 volts potential going to the audio setup. I always like to use only one leg of the transformer split out on the pole or one breaker. In my opinion there is a chance of more problems using both sides of the transformer allthough some audio installations use a split transformer to reduce posible noise. So its all in how you look at it.
greg
Really, if you feed two equipment from a separate breaker, one on one side of the 240 volt transformer and one on the other, with the transformer center tapped and becoming neutral, the two sides of the voltage cancel. Or at least the possible electrostatic charge is neutralized to zero. But that would onlt seem to work if both pieces of equipment had identical power supplies in every respect.
greg
On Jun 11, 11:10=A0am, "Dave Plowman (News)" wrote: >
Not different as in 3 phase but split phase. It is very common to have
240 Volt service into the house from a center tapped transformer. The high power devices like ovens, A/C, water heaters, clothes dryers get the full 240 volts fromt the 2 outer feeds. The rest of the house gets the center tap 'neutral' and one of the 2 outer feeds via a circuit breaker. Because the loads may not be balanced across 2 'phases', the neutral will not be the same between various outlets.There is your 'ground loop' when you plug in devices that tie the neutral to the chassis.Now tell me how the mains wiring is done in a typical UK residence. Do you get 480 center tapped? My guess is 'no' but I have no certainty. Do you get just 2 wires from the transformer. Is one end of the 240V feed tied to earth? Does that earth lead build up voltage drops in the building giving you essentially the same problem we have in the US ?
G=B2
I don't know of any modern piece of equipment that ties the neutral to the chassis. Ground, yes. Surely if you did tie the neutral to the chassis and it's fed from a two pin reversible plug - which I assume you still have in the US - and the plug is reversed, you then get the full 110v on the case?
In most town situations, one transformer covers a large area - but that is to step down the high distribution voltage to the 240 volts. This produces three phases - all 240v - and neutral is ground. Between phases you get
440 volts. This three phase plus neutral (ground) is fed along the street, and only one phase (usually 100 amp max) is fed to a house. Alternate phases are use to other houses to balance the load. A very large house may have a second phase - but electric heating isn't common in the UK due to cost so up to 100 amps (25kW) is more than enough for most.There are different ways of providing the safety ground - but on a modern supply its usually by combining the neutral and house earth at the termination point of the feeder cable. All metalwork in the house - water pipes etc are bonded to this point too. Latest regs have a split load central consumer unit ('fuse box') with each half having an RCD. Then MCBs for the various circuits. Something like a four bedroom house would normally have a 32 amp ring circuit for the power sockets in the kitchen, another for the ground floor and another for everywhere else. There is no limit to the number of outlets on a ring (in most circumstances) and each can carry up to 13 amps ( 3kW approx) Now of course this sounds strange since a 32 amp circuit would be limited to 3 fully loaded sockets and it is common to have a great deal more - but anything which is permanently installed like a water heater will have its own radial circuit. And most of the things you plug in take only a small current. Apart from in a kitchen - hence the fitting of one or two rings dedicated to it.
As regards a sound system, that will likely all be in one room so all on the same circuit.
The earth loop impedance is tested at installation time and mustn't exceed
1.88 ohms for a 32 amp ring. In most cases it will be much lower. (The ECC consists effectively of two 1.5mm² wires in parallel.
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Dave Plowman dave@davenoise.co.uk London SW
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"Dave Plowman (News)" wrote in message news: snipped-for-privacy@davenoise.co.uk...
(snip)
If there are indeed three phases, would not the phase to phase voltage be 220v times sqrt(3) = 381v?
David
Voltage in the UK is still 240v - although the tolerance has been altered to bring it into line with Europe so is quoted as 230v.
3 phase distribution boards are normally marked 'danger 415v'Dunno where I got the 440 from. ;-)
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Dave Plowman dave@davenoise.co.uk London SW
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In the US, whether it's 440V or 480V depends on whether the three-phase transformer is "delta" or "wye" connected. Same for 220/240 and 110/120.
Isaac
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