Dedicated 20 amp lines/should i use a sub panel

Besides having built-in noise cancelling features, and surge protection, another advantage to the sub-panel is that you end up with a star grounding scheme that is short, and therefore much less likely to cause differences in ground potential.

The biggest source of noise in my mind is usually other household appliances, and dimmer switches. If you get separate runs, without any noise cancelling, you are literally just making it easier to pick up noise from anywhere in the house. Having a 30 to 60 Amp subpannel that has its own noise and surge protection is the key.

Best,

E

Jim,
8/2 with ground. You are correct about the legs. I also tried it on both legs. So instead of 22, 24, where I originally connected it, I had tried it on 23, 24 but it still hummed. In fact, as it’s a basement space, I just ran in a 12/2 on 15A breaker on the same leg to see if it still hummed with the (2 wire) monos. It did. But it doesn’t when I add my REL sub. So all is not lost! I should say that there is normally no hum from the rig.

How far away is the main panel from your listening room? If it’s more than 50 feet then it pays to put in a subpanel since a branch circuit of that distance will have a high voltage drop (3 volts with #12 and 1.8 volts with #10 at a 15-amp peak draw).

If distance is not an issue, use 10/3 romex because the wires are spiraled and that reduces common mode noise. Cut the bare grounding conductor and use the red wire for ground (tape it green where exposed, of course). Also, use the clamps under the screw of the receptacle for #10 wire instead of looping it around the screw. And use 10/3 from the subpanel to the receptacle also.

@noromance,

From the picture of one of your mono amps you are not using the green safety equipment ground wire. I assume both amps are wired that way.
https://systems.audiogon.com/systems/1593#&gid=1&pid=11

How about the preamp, are you using the safety equipment ground on it?

I also noticed the steel cover plate on the single receptacle outlet.
https://systems.audiogon.com/systems/1593#&gid=1&pid=14
Not that it would cause the hum issue, it could have an effect on the SQ. Just for the heck of it pull the steel cover off the outlet and see if you can hear a difference. If yes just install a nylon plate in its’ place.

By the way, nice looking vintage equipment.


Just an added note.
I ran two 10-2 with ground NM-B cables, (Romex is a Trade Name manufacture of NM-B sheathed cable), around 75ft each in length. Preamp and amp are tube. System is dead quiet. Ear right up next to the drivers of each speaker.


Jim

Jim,
Thanks. Correct - that’s how I received it from the seller. Not sure if Stu R. originally did that or if it was the seller. As the REL is fine and grounded, the hum loop may be from the monos. I dunno. The Croft preamp has the safety ground intact as factory supplied. The 401 is also grounded. Interesting notes on the steel plate. However, I’ll definitely try it on the DIY 4 duplex receptacle unit if I can buy one in that size. Thanks for your help and apologies to the OP for going a little off-topic.