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Old 2nd December 2010, 07:35 AM   #1
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Default wire thickness

I am about to rebuild a lampizator, I am wondering about wire diameter...obviously there is a mininum diameter required depending on voltage/current...but is there a advantage to sound if you increase the diameter or add more wires...for instance should your ground wires be single strand as thick as practical or should it have as many strands as practical? (I have quarter of a meter of lightning conductor copper)

Also I see builders twisting wires together...for AC I have read this is for emf emission..but what about DC? Does twisting wires together make a inductor ? If you make an inductor do you create higher resistance in the wire? Or practically is it all a fuss about nothing?
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Old 2nd December 2010, 09:14 AM   #2
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Quote:
Originally Posted by chokesrule View Post
I am about to rebuild a lampizator, I am wondering about wire diameter...obviously there is a mininum diameter required depending on voltage/current...but is there a advantage to sound if you increase the diameter or add more wires...for instance should your ground wires be single strand as thick as practical or should it have as many strands as practical? (I have quarter of a meter of lightning conductor copper)
Doan worrybouddit. I use regular wire (same as used for the AC power cord) for grounds. The whole point of star grounding is to keep voltages from capacitor charging out of signal paths. That's a problem when signal and DC share the same return path, as they will if you simply ground everything directly to the chassis. This is unavoidable when doing RF designs, but there the over riding concern is minimization of return path inductance. RF circuits already reject frequencies as low as the capacitor charging pulses, but these lie right in the audio passband, and so you need to keep them out of signal paths. If the gain is high enough, even an ohm or two across a chassis can get enough PS hash into the signal path to make for annoying hum at the speeks.

You're not gonna see huge currents unless you're doing a solid state design, so no need to get carried away with using really heavy duty wire. It can't do any harm, but it's likely to cost more and be harder to work with.

I prefer to work with stranded unless I have reason not to.

Quote:
Also I see builders twisting wires together...for AC I have read this is for emf emission..but what about DC? Does twisting wires together make a inductor ? If you make an inductor do you create higher resistance in the wire? Or practically is it all a fuss about nothing?
Twisting the wires makes an "uninductor". The spiral means that the wire is constantly changing orientation to magnetic fields, resulting in nulling. It's a good idea to twist any carrying AC (e.g. heater leads) and signals. Can't hurt to twist DC carrying leads as well to help prevent the induction of AC into those leads.
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Old 2nd December 2010, 12:08 PM   #3
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hi, Miles, your answer has given rise to more questions about grounding..

Currently (no pun intended) ALL my earths whether signal or power or chassis are on seperate wires but meet at one point which i take it is the "star" ..... This central point then is linked to mains/ household earth.....

1)Are you saying then that the signal earths should have no interaction with chassis and power earths? Should the signal earths be linked to mains thru a separate path? Or: not connected to anything but their collective selfs: a sort of virtual signal earth?I have often wondered why you read about keeping the rca sockets insulated from the chassis when they are are linked at the star....

2)If capacitor charging pulses can end up in the audio band...then my next layout should keep ALL psu components as far away as possible from the valves and signal lines....ie it would be better to have all psu caps in a separate chassis and linked to the valve base via long wires....I currently have the last anode capacitor soldered right onto the anode pin of the valve seat

3) it seems that we are using the mains earth to get rid of all the electrical noise etc . So can it be supposed we are connecting super sensitive audio kit to a noisey mains earth??Can some of this noise (e.g fridges,lights and so on) end up in our audio thru the earth? So if I wanted to make sure my audio earths did not pick up any pollution(from linking it to the household earth) would placing say a small value resistor in series to the wire connecting star earth to household earth prevent any mains earth contamination of my audio...Or is it worth the effort?
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Old 2nd December 2010, 01:15 PM   #4
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Signal earths should have one direct connection to safety ground, and indirect connections in every other piece of equipment. The connection is for safety. The indirect aspect is to reduce hum loops. RCA sockets should be isolated from the chassis at the point of mounting as they are part of the signal ground whereas the chassis is part of the safety ground. There will be a connection between them somewhere, but you don't want two connections as that is a loop and loops hum.

You need to keep charging pulses away from the audio. This does not require great distance, merely careful wiring. For example, the output leads from a solid-state bridge rectifier (whether packaged or made from 4 diodes) should be kept near each other, even twisted, as far as possible right up to the reservoir capacitor terminals. The rectifier input leads too, as these carry the same current pulses but with alternate phases reversed.

It doesn't matter too much if the mains earth is noisy, provided all your audio is referred to the same point. Ideally the mains ground should be star-wired i.e. all should plug into the same wall socket, via multi-way adaptors. Fridges etc. are often picked up on speaker leads, not mains leads.
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