Dedicated 20 amp lines/should i use a sub panel

I agree with dill as well, no need for a sub panel, jmho.

noromance
899 posts                                                                       01-03-2018 10:23pm

I ran 2 x 20amp runs on 10 gauge from 2 side by side breakers for monoblocs. I ended up not using one of them because of a hum loop. Let us know how you get on.

@noromance,

By side by side, do you mean the breakers are installed directly across from one another? Connected to the same main bus breaker tie. (Both are fed from the same leg, Line.)
Or, do you mean one is installed above the other, side by side? One fed from leg, Line 1 and the other fed from Leg, Line 2?

Did you use Romex?
Did you try to keep the 2 cables separated from one another at least 6" after getting them out of the electrical panel, as soon as practical? Especially a long parallel run?
Is it possible one of the 2 is running parallel next to some other branch circuit?

Jim

noromance
901 posts                                                                     01-04-2018 12:07pm

Jim, Some replies below.

By side by side, do you mean the breakers are installed directly across from one another? Connected to the same main bus breaker tie. (Both are fed from the same leg, Line.) Or, do you mean one is installed above the other, side by side? One fed from leg, Line 1 and the other fed from Leg, Line 2?
>>> Same leg/busbar. One 20A breaker above other.

>>>

Same leg/busbar. One 20A breaker above other.

If the breakers are directly above one another, there in on the same side of the electrical panel, they are not fed from the same leg/bus bar. (For standard size single pole breakers.) One is fed from one leg, Line, and the other is fed from the other Leg, Line.

You can easily verify this with a multimeter.
Insert one test probe in the Hot contact of an outlet fed from one dedicated circuit and the other test probe in the Hot contact of the other dedicated circuit outlet.
~ If both are fed from the same leg, Line, bus bar, the meter will measure zero volts.
~ If the meter reads 240V, nominal, then one circuit is fed from one leg, Line, and the other circuit is fed from the other leg, Line.

Did you use Romex?
>>> Yes. 8/2 NM-B (not 10 as I said before) cable from Lowes.

8-2 with ground? Not 8-3 with ground?

Jim

@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

noromance said:

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.

The DIY 4 duplex plate appears to be stainless steel. It may or may not have ferrous materials in it. It depends on the grade quality of the stainless steel. You can use a magnet to check it. If the magnet sticks to the plate like glue or is attracted to the plate replace it with a non breakable nylon plate. Change that single receptacle steel cover plate if that is the outlet that’s feeds the DIY power distributor.

Jim

Al, (almarg),

By chance have you been following the exchanges between noromance and me in response to this post of his?

noromance
904 posts                                                                                                 01-03-2018 10:23pm

I ran 2 x 20amp runs on 10 gauge from 2 side by side breakers for monoblocs. I ended up not using one of them because of a hum loop. Let us know how you get on.

Both mono block amps are floating the safety equipment ground.

When everything is fed from one dedicated circuit no hum.
When the other dedicated circuit is used to feed the other amp he gets the hum.
Is there a chance the hum is not caused by a difference of potential between the two equipment grounds of the two dedicated circuits?
Just a gut feeling I don’t think the equipment grounds are causing the hum.

And how would you explain this?

noromance
904 posts                                                                                                  01-04-2018 2:29pm

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.

But it doesn’t when I add my REL sub.

???

Any ideas? Suggestions?

How about if the mono amps are using an AC Line filter cap/s and maybe one or both is leaking to the chassis of the amp. What if the hot and neutral AC polarity is reversed on one amp with respect to the other?
https://systems.audiogon.com/systems/1593

Again, any ideas?

Jim

noromance
906 posts 01-04-2018 11:20pm

Looks like I should expedite my plan to rewire the power cords on the power amps with new OFC cables including connecting the safety ground. I’ve been meaning to do it after changing the power cord on the preamp with very positive results. Thank you.

@ noromance,

Is this the schematic wiring diagram for your amps?
http://www.freeinfosociety.com/electronics/schematics/audio/pictures/eicohf22.gif

If so, see that C13 (.03 600V) cap connected to the AC line that is connected to the chassis? (Just to the right of the AC line fuse). That would have to be removed before connecting an equipment ground wire to the chassis.

That’s the cap I was attempting to ask Al about in my previous post. I forgot it was/is referred to as a "death cap". (Thanks imhififan for the 2 Links above.)
I always wondered why the cap was installed on the fuse AC line and not on the non fused line. With the old original non polarized plug the user had a 50/50 chance of plugging the plug into the wall outlet and getting the neutral, (The Grounded Conductor), the line the cap is connected to. Again note the fuse would be connected to the neutral line.
I guess back in those days electrical safety was seen different than it was in later years.
One example, old Knob and Tube wiring the HOT was ran directly to the ceiling light and the neutral ran through the switch on the wall.


The amps, at the time they were designed and built, were not designed to be directly connected to an equipment ground. You will be connecting the amplifier’s circuit ground/signal ground directly to the mains safety equipment ground. I am not sure if that will improve the SQ of the amps or harm it. Someone like Al or Ralph would need to chime in with their thoughts.

Jim

Al (almarg),

Thanks for responding to my above post. I was thinking the same things as you stated in your last post. And no doubt circuit grounds/signal grounds are more than likely connected to the chassis at various places.

Would you leave the cap where it is now located on the same AC line as the fuse? For proper operation the cap should be connected to the neutral conductor. Problem with the way it is now the neutral is fused. (I remember reading somewhere the user should reverse the 2 wire plug in the wall outlet for what sounded the best with the least, buzz/hum/noise.)

I think for a test I would first lift the cap from the chassis and then check for the proper, correct, AC polarity orientation for the primary winding of the power transformer. That will determine which lead of the primary winding should be connected to the Hot conductor and which lead of the winding should be connected to the neutral conductor. Hopefully the AC line that is fused will be the Hot. There’s 50/50 chance. I doubt back when the amps were built anybody back then checked.
At any rate if possible I would want the fuse on the Hot mains conductor and the cap connected to the mains neutral conductor to chassis ground. I would check and wire both amps the same. (Of course for many years the plug for the amps were a 2 wire non polarized plug that had a 50/50 chance of the fuse being fed from the mains Hot conductor.)

Al, what do you think?

Jim

Al,

Thanks for responding to my post.

Jim

@handymann

Every other single breaker space down each side of an electrical panel is the other Leg, Line.

Example for a 120/240V single phase electrical panel:

First top breaker space on the left side is L1. The first top breaker space on the right side L1.

The second space on the left side is L2. The second space on the right side is L2.

The third space on the left side is L1. The third space on the right side is L1.

The forth space on the left side is L2. The forth space on the right side is L2.

And so on down each side of the panel.


NOTE:

Some GE single phase load centers have a funky breaker connecting bus that will accept standard size breakers as well as "slim" size breakers. With this load center if 2 slim single pole breakers are installed side by side on the same side of the panel it is possible both may be connected to L1 or both connected L2 Or one might be on L1 and the other on L2.

To make thing even more confusing there is a 2 pole "slim breaker" for 240V loads.

Extreme care must be taken when using this GE load center. There may have been other manufactures that use standard and slim style breakers as well. GE is the only one that I know of.

https://www.superbreakers.net/1-pole-circuit-breakers/thqp120

https://www.lowes.com/pd/GE-Q-line-Thqp-20-Amp-2-Pole-Standard-Trip-Circuit-Breaker/1099039

Jim