Dedicated line questions...

I have read through this post and I noticed some folks here use both lines from the distribution panel.   That is, line 1, line 2, neutral, and earth, such as would be wired when using the Southwire 10 awg, 3 wire.  Since line 1 and line 2 are opposite in phase for North America (and anywhere else where split phase lines are used) that means hum is more likely to occur since the outlets are no longer identical polarization.   If you are using an isolation transformer and feeding it 240 VAC then stepping it down to 120VAC, then this doesn't apply.   But if you don't have an isolation step down transformer, then you might get some hum.   I see the point for 10 awg wire and a dedicated line, but I don't see the point for using both lines without a transformer.   That really is counterproductive.

This is an example of a isolation transformer, step down.  Feed it 240VAC in and get 120VAC out at 2x the current capacity.   https://talema.com/wp-content/uploads/datasheets/MD.pdf   This is not a plug in product btw, this is either DIY or look for an equivalent factory made unit you can just plug in.

@spatialking... that is essentially what the Decware ZLC is. I have looked at the reality of installing a line from my breaker to where I need it, and it would be a serious PITA to run new cable to that area. Basically across the entire house, in the attic, through vaulted clients etc. no way to go under... 

It was a lot easier for me to run my dedicated circuits. I ran 6. You don't want to have dimmer switches, or other appliances on the same audio circuit. I live in a log home with a crawl space. You can actually walk in when entering, then it becomes more of a crawl. I ran my 10awg (exterior wire) from the breaker box, 6 20amp breakers, carefully stapled the wire to the floor joist. I had drilled the holes close to the exterior log wall, pushed all the wires through the pine floor, make sure you leave enough on each end. I used Furutech NFC Rhodium outlets. I even soldered the ground connector, and spade connectors as to have a proper contact. OCD all the way! I just mounted the junction boxes to the wall. I wrapped all the wire in black. what you do see has a retro look. With drywall or fishing wire through it would be a lot harder to do! All these things, cables, outlets, dedicated circuits are accumulative. If you have a revealing system all these things make incremental improvements. 

spatialking323 posts

01-08-2021
7:09pm

I have read through this post and I noticed some folks here use both lines from the distribution panel. That is, line 1, line 2, neutral, and earth, such as would be wired when using the Southwire 10 awg, 3 wire. Since line 1 and line 2 are opposite in phase for North America (and anywhere else where split phase lines are used) that means hum is more likely to occur since the outlets are no longer identical polarization.

@spatialking
I suggest you reread the thread again. No one mentions using both Lines, legs, (therein a 120/240V multiwire branch circuit), to feed a single dedicated 120V branch circuit.

I think you misunderstood what @gs5556 meant when he recommended using 10-3 with ground Romex for a 120V dedicated branch circuit.

FWIW, 3 conductor with ground NM sheathed cable (Romex is a Trade Name of Southwire) is not designed/manufactured only for use for 120/240V multiwire branch circuits. 3 conductor with ground is also used for 3 way switching of lighting as well as split duplex receptacle(s) switching for table lamps. Top receptacle of duplex is hot all the time, bottom receptacle is switched by a wall switch.
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