Bodgit

Dedicated HiFi circuit design

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There is a big difference between (as posted elsewhere) impedance and resistance. The resistance of connections (obviously measured with no connections unless you really want to fry yourself) should be as close to zero as makes no difference. If you're suggesting you've measured 18 ohms, bin it. Any serious load and that's going to generate serious heat.

Impedance is a totally different thing and not something you can measure simply when you are talking about the impedance of an AC voltage supply.

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10 minutes ago, rabski said:

There is a big difference between (as posted elsewhere) impedance and resistance. The resistance of connections (obviously measured with no connections unless you really want to fry yourself) should be as close to zero as makes no difference. If you're suggesting you've measured 18 ohms, bin it. Any serious load and that's going to generate serious heat.

Impedance is a totally different thing and not something you can measure simply when you are talking about the impedance of an AC voltage supply.

18Ω was recorded between L-E and the socket (which was the cause of the high reading) was replaced. I’ve come across many melted terminations and sockets due to the heat generated under such conditions.

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4 minutes ago, Blackmetalboon said:

18Ω was recorded between L-E and the socket (which was the cause of the high reading) was replaced. I’ve come across many melted terminations and sockets due to the heat generated under such conditions.

I've seen a few as well. I'm fussy these days about the sockets I use. You'd have thought that BS would ensure consistent quality, but I've seen some dire s**t around.

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4 minutes ago, rabski said:

I've seen a few as well. I'm fussy these days about the sockets I use. You'd have thought that BS would ensure consistent quality, but I've seen some dire s**t around.

In this case the likely culprit was environmental (cold and damp) and age. 

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Of course mains makes a difference sonically, its just a matter of how and to what extent. Putting in a dedicated main supply for a hifi might, to some, seem like a waste of time since they "won't hear any difference". That may well be the case.

However if I'm rewiring the entire house, I don't see why one would not put in a dedicated mains circuit with a decent cross sectional area, since you only have a minute but of time and money to lose.

So, 6 unswitched double MK sockets on a 4mm ring (rather than radial, adding in the return doubles the x-sectional area), connected to a 32A MCB at the CU seems my favoured option right now.

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Posted (edited)
1 hour ago, Bodgit said:

Of course mains makes a difference sonically, its just a matter of how and to what extent. Putting in a dedicated main supply for a hifi might, to some, seem like a waste of time since they "won't hear any difference". That may well be the case.

However if I'm rewiring the entire house, I don't see why one would not put in a dedicated mains circuit with a decent cross sectional area, since you only have a minute but of time and money to lose.

So, 6 unswitched double MK sockets on a 4mm ring (rather than radial, adding in the return doubles the x-sectional area), connected to a 32A MCB at the CU seems my favoured option right now.

i notice above you mention that you would fit 6 (3 x 2 double mk) sockets if installing a dedicated hifi circuit.

has any company, hifi or otherwise, ever built 4, 6 or 8 sockets in a row ?

such a set up would then make extension blocks (to an extent) obsolete.

(i believe russ andrews recommends ring rather than spur set ups but as someone jokingly pointed out it was so he could sell twice as much cable !)

Edited by Turk 182

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2 minutes ago, Turk 182 said:

i notice above you mention that you would fit 6 (3 x 2 double mk) sockets if installing a dedicated hifi circuit.

has any company, hifi or otherwise, ever built 4, 6 or 8 sockets in a row ?

such a set up would then make extension blocks (to an extent) obsolete.

You can get triple socket back boxes and triple socket fittings, but I'm fitting 6 doubles, so 12 sockets in all. I counted how many I might need, and concluded 12 should cover it!

So 6 doubles, plus a double back box for 4xCat6 RJ45 sockets and another single for a quadplex satellite/UHF outlet.

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8 hours ago, Bodgit said:

So, 6 unswitched double MK sockets on a 4mm ring (rather than radial, adding in the return doubles the x-sectional area), connected to a 32A MCB at the CU seems my favoured option right now.

With a Ring Final Circuit (to give it its proper name) you are actually splitting the load between the two legs back to the consumer unit. How even the split is will depend on how far the electrical loads are compared to the midpoint of the ring. 

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3 minutes ago, Blackmetalboon said:

With a Ring Final Circuit (to give it its proper name) you are actually splitting the load between the two legs back to the consumer unit. How even the split is will depend on how far the electrical loads are compared to the midpoint of the ring. 

I don't see the point in Ring circuits anymore,and very tough to get a socket in the exact mid point so the load will travel down the leg with the least resistance (the shortest leg). If I was putting in a Dedicated HiFi circuit a 20 amp 4mm radial should do.

Have you worked out the total electrical load of you system ?

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16 minutes ago, FrankD said:

I don't see the point in Ring circuits anymore,and very tough to get a socket in the exact mid point so the load will travel down the leg with the least resistance (the shortest leg). If I was putting in a Dedicated HiFi circuit a 20 amp 4mm radial should do.

This isn’t strictly true. The saying “Electricity/current follows the path of least resistance” is actually incorrect. 

With mains voltage (230V AC, 50Hz) it is the impedance that is important and current flows in inverse proportion to the impedance of the paths. So current presented with two paths back (one high impedance and one low impedance) the majority will follow the path of low impedance but some current will still follow the high impedance path.

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2 minutes ago, Blackmetalboon said:

This isn’t strictly true. The saying “Electricity/current follows the path of least resistance” is actually incorrect. 

With mains voltage (230V AC, 50Hz) it is the impedance that is important and current flows in inverse proportion to the impedance of the paths. So current presented with two paths back (one high impedance and one low impedance) the majority will follow the path of low impedance but some current will still follow the high impedance path.

Just in the same way as two resistors in parallel work in a dc circuit, the current will flow in proportion to the resistance.

In reality, the current flowing due to the demands of hifi gear is two tenths of bugg4r all compared to electric hobs or even a kettle.

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12 minutes ago, Blackmetalboon said:

This isn’t strictly true. The saying “Electricity/current follows the path of least resistance” is actually incorrect. 

With mains voltage (230V AC, 50Hz) it is the impedance that is important and current flows in inverse proportion to the impedance of the paths. So current presented with two paths back (one high impedance and one low impedance) the majority will follow the path of low impedance but some current will still follow the high impedance path.

Maybe my words where a bit misleading, but like you say the majority will follow the path of low impedance.

Still can not see what the benefit of running a ring rather than radial is, be interesting to know what the load of the system is, and whether a 32 amp circuit is required.

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7 minutes ago, Fourlegs said:

Just in the same way as two resistors in parallel work in a dc circuit, the current will flow in proportion to the resistance.

In reality, the current flowing due to the demands of hifi gear is two tenths of bugg4r all compared to electric hobs or even a kettle.

Yes, the reason I stated mains voltage is because it can follow different paths depending on wether it’s AC, DC and its frequency (Hz).

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18 minutes ago, Fourlegs said:

In reality, the current flowing due to the demands of hifi gear is two tenths of bugg4r all compared to electric hobs or even a kettle.

8 minutes ago, FrankD said:


Still can not see what the benefit of running a ring rather than radial is, be interesting to know what the load of the system is, and whether a 32 amp circuit is required.

I’d like to say that a Hifi will never pull that much but, this is the Wam, someone out there will be actively tri-amping their speakers with six behemoth sized, Class A power amps!:D

Generally I think the most likely problem (even this will be very, very rare) will be nuisance tripping caused by inrush current when switching on large amplifiers.

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Posted (edited)
1 hour ago, FrankD said:

I don't see the point in Ring circuits anymore,and very tough to get a socket in the exact mid point so the load will travel down the leg with the least resistance (the shortest leg). If I was putting in a Dedicated HiFi circuit a 20 amp 4mm radial should do.

Have you worked out the total electrical load of you system ?

A 5A circuit will power a 1kW amplifier. How much power does yours have?

Ring circuits are to save copper. They double the current carrying capacity of the cable used. There are no disadvantages of a ring circuit and we are also fortunate that our mains plugs are so well designed. The best in the world in fact.

Edited by Muckplaster
addenda

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