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PostPosted: January 24th, 2018, 11:48 am 
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tomp wrote:
At line frequencies or other low frequencies the best shielding is distance. That is why I try to put transformers in a separate housing away from the audio circuits. In with the transformer is the rectification and one stage of filtering so I am sending DC over the interconnect which will reduce radiated energy. If you can't do that then placement and orientation of the transformer can help. If none of those work, high permeability materials such as mu metal can be used. Here is a useful link:

https://en.wikipedia.org/wiki/Electromagnetic_shielding


Ok. I will separate the PS and pre-amp. What kind of cables and connectors do you recommend between PS and Preamp. It will have 250VDC and two 6.3VAC 4A for the filaments. Since I am going to rebuild anyway, I might rectify the filament supplies also.


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PostPosted: January 24th, 2018, 12:00 pm 
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Loose connections can do more than damage the music. They can damage your house. If for example you have an outlet on a 15 amp line you can provide 15 amps to that outlet all day long without tripping a breaker. A loose wire connection to that outlet that had a resistance of only 1/2 ohm would result in a power dissipation on that wire of over 100 watts. Considering that a typical soldering iron has a power of between 25 and 35 watts you can imagine what 4 times that heat on a continuous basis will do to the surrounding materials. I once had a loose connection on the back of an old style round glass fuse holder and over time it melted the insulation all the way to a point where the wire was against the metal box. I happened to be working near the box that day and hear a very loud buzzing noise as the wire arced to the box. Since it was on the incoming side of the fuse and since the box was separate for the water heater there was no other fuse between the the box and the power pole. As soon as I got my wits about me I pulled the disconnect switch and then proceeded to change my pants. It is a real problem.


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PostPosted: January 24th, 2018, 12:11 pm 
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Cogito wrote:
tomp wrote:
At line frequencies or other low frequencies the best shielding is distance. That is why I try to put transformers in a separate housing away from the audio circuits. In with the transformer is the rectification and one stage of filtering so I am sending DC over the interconnect which will reduce radiated energy. If you can't do that then placement and orientation of the transformer can help. If none of those work, high permeability materials such as mu metal can be used. Here is a useful link:

https://en.wikipedia.org/wiki/Electromagnetic_shielding


Ok. I will separate the PS and pre-amp. What kind of cables and connectors do you recommend between PS and Preamp. It will have 250VDC and two 6.3VAC 4A for the filaments. Since I am going to rebuild anyway, I might rectify the filament supplies also.


My typical answer. It depends. Assuming the currents are low and you don't need locking devices I often use round DIN plugs and sockets. In your case with 250 VDC, I would look at another type of connector because the typical rating of a round DIN plug is 100 VAC. I would go to Digikey, Newark, or Mouser and look at some of the connectors. The old standby Amp 97 series connectors are very good and won't break the bank. They are also locking. We used them on electronic flash units with voltages of 900 VDC and discharge currents as high as 1KA.

https://www.digikey.com/en/product-high ... connectors


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PostPosted: January 24th, 2018, 12:14 pm 
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An octal socket on the live end and an octal plug should be fine at those voltages/currents.... Most octal plugs don't have any kind of strain relief, but if you're not plugging/unplugging it all the time, that shouldn't be too much of a problem.

Roscoe

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PostPosted: January 24th, 2018, 12:39 pm 
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ratbagp wrote:
To change the subject slightly. In many parts of the world, installation of solar panels and batteries is increasing rapidly. Most systems are still connected to the grid but some are off-grid.

If you were to install either system, what would you do to maximize the quality of electricity used by your amplifier?

ray


I'd install a 48Vdc battery system as part of the solar system and run the stereo directly off the 48Vdc supply. There are some decent pure sine wave inverters out there if you insist on running things on 120Vac, you'd just need to do some research. If most of your household ran on DC, you could even run a separate inverter for each piece of equipment requiring 120Vac;)

Ham radio sites are a good place to start on the research, we don't like RFI any more than audiophiles ;)

Roscoe

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PostPosted: January 24th, 2018, 12:48 pm 
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Roscoe Primrose wrote:
An octal socket on the live end and an octal plug should be fine at those voltages/currents.... Most octal plugs don't have any kind of strain relief, but if you're not plugging/unplugging it all the time, that shouldn't be too much of a problem.

Roscoe


I have two 250VDC and four 6.3V(AC/DC) and a ground. How does the cabling work? Dont I need to run three separate cables (tied together)?


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PostPosted: January 24th, 2018, 12:52 pm 
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Cogito wrote:
Roscoe Primrose wrote:
An octal socket on the live end and an octal plug should be fine at those voltages/currents.... Most octal plugs don't have any kind of strain relief, but if you're not plugging/unplugging it all the time, that shouldn't be too much of a problem.

Roscoe


I have two 250VDC and four 6.3V(AC/DC) and a ground. How does the cabling work? Dont I need to run three separate cables (tied together)?


That's basically what I did for my tube phono stage. Two coaxial cables for the L/R B+, twisted pair for the heater supply. All tied together every few inches with zip-ties. Split loom or braid might be a more visually appealing solution to keep the cables together. It probably makes sense to put at least the last PS filter stage in the electronics chassis to filter out anything that might have been picked up in the cables from the PS.

Roscoe

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PostPosted: January 24th, 2018, 1:49 pm 
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tomp wrote:
Loose connections can do more than damage the music. They can damage your house. If for example you have an outlet on a 15 amp line you can provide 15 amps to that outlet all day long without tripping a breaker. A loose wire connection to that outlet that had a resistance of only 1/2 ohm would result in a power dissipation on that wire of over 100 watts. Considering that a typical soldering iron has a power of between 25 and 35 watts you can imagine what 4 times that heat on a continuous basis will do to the surrounding materials. I once had a loose connection on the back of an old style round glass fuse holder and over time it melted the insulation all the way to a point where the wire was against the metal box. I happened to be working near the box that day and hear a very loud buzzing noise as the wire arced to the box. Since it was on the incoming side of the fuse and since the box was separate for the water heater there was no other fuse between the the box and the power pole. As soon as I got my wits about me I pulled the disconnect switch and then proceeded to change my pants. It is a real problem.



It is not only very true, but it is a code requirement in D.C. to perform preventive maintenance (P.M.) every three years. Other jurisdictions don't specifically call for it but the accepted industry practice is to perform electrical P.M. at least every five years. I had a client that lost a switchboard to the tune of $250,000 because it wasn't P.M.'d -- it actually went out in flames.

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PostPosted: January 24th, 2018, 3:19 pm 
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when I did my "PM" on this house when I set up my system in 2003 it took me just a couple hours time to check and clean all the ground connections, inside and out, the tighten all the connections in the breaker box. Last year I put in a 20amp dedicated circuit using 10ga to my listening room. It was a real pain to deal with thios stif wire stringing in the walls and to the new heavy duty outlets. I also made power cables to my power amps with this wire. Things could have been easier if I used a lessor ga ground wire which I understand is withing code


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