hum problem - help needed

[spherop]

I recently had an electrician rewire 3 outlets in my home studio with an isolated ground.

I think this new wiring may have introduced a hum problem - tho I am not sure - and would like advice if anyone has any.

I get the whirring hum sound when using a pendulum quartet but not when using a joe meek or a line 6 pod (the units I've tested so far).

The pendulum never hummed before the new wiring.

The reason my mind went to a wiring problem is that the pendulum is the only unit of the three with a three prong plug - the others have ac units.

Why would the introduction of an isolated ground add hum? Or am I likely off base on my assessment?

Any thoughts appreciated.

[JohnnyTooLoud]

Can you explain "Isolated Ground."

There should only be one ground point at that is at the main service. You can have multiple ground rods (we do) but they need to tie in at your circuit box. So if all he did was take power from your main service and then send the ground from those outlets to a different ground you could be having all sorts of fun in there.

So please give us more details.

--JTL

[spherop]

I wish I understood more about this to be better at explaining.
The term isolated ground - I think is what the electrician used.
Basically he pounded a 15' rod into the earth - then I believe he connected that to the outlet grounds and also to something in the basement - but I am not sure if he did as you said to 'tie them into the circuit box'.

Is that what I should verify with him?

And what is '' exactly?

Thanks for the help.

Originally posted by JohnnyTooLoud
Can you explain "Isolated Ground."

There should only be one ground point at that is at the main service. You can have multiple ground rods (we do) but they need to tie in at your circuit box. So if all he did was take power from your main service and then send the ground from those outlets to a different ground you could be having all sorts of fun in there.

So please give us more details.

--JTL

[Jason Poulin]

Sherop,

I am an electrician so hopefully I can help.

An Isolated system is any system that is not conductively connected to distribution system. That's your panel. Meaning it's not grounded to your panel. Is that correct? follow your ground wires. (bare copper wires)

I don't know why he would have installed another ground rod into your studio. He must have ran the cable to the panel to get power so, where is the logic?? .

You do have a panel that's grounded correct? It should be either grounded to your main cold water pipe or to a ground rod. Anyhow, check and make sure his attachment are secure (tight). Open your outlets, make sure that they are attached to ground (copper wire attached to the outlets) make sure all those copper wires are attached securely to the grounding rod. Or unless he grounded them at your panel, make sure that the ground is securely fastened into the ground bus. Make sure that bus is secure to your main system ground (ground rod from panel or to water pipe)

Make sure that your white conductors(neutral or identified cond.) are connected properly to the neutral bus bar ( there should be a whole bunch of them attached to it ) and your black (hot) conductors are into a breaker or fuse receiving power.

Try pluggin your Pendulem using an extention chord into another outlet (one that you know he didn't fiddle with) If the problem still is there and you didn't have it before, maybe your unit needs a tune up. Make sure that all connections of grounding conductors are all bonded to your 3rd prong including the casing if it's metal.

Anyhow, that should be everything that is concerned with the grounding. Like I said, if it is a seperate ground that he ran into your system, well maybe it wasn't such a good idea...

THIS IS ONLY TO MAKE SURE THAT IT'S PROPERLY GROUNDED so it MAY be in the wiring. As an electrician, that's what I would look for. I'm not an audio equipment specialist. Maybe Fletcher or some other dudes on this site can help if the problem persists after verifying the electricians work.

Good luck.

Jason

[juniorhifikit]

Ground is never actually zero. If you connect two pieces of gear together but they're powered from two separate circuits (with different ground potential), current will flow through the ground path and cause a buzz.

Uh, I think.

All your stuff should be grounded in the same place/to the same ground potential.

[Jason Poulin]

That's what I thought too...

Why would someone ground somewhere else than the panel if they are acutally running the feed from it. There is a potential but I don't know if it would cause a buzz.

What I am thinking... How old is your studio - the building that is? Before, they didn't have to run ground wires to an outlet and just relied on the neutral conductor (all of that has changed)

The electrician might just spliced into one of the circuits which had no ground and decided to run one outside instead of running back to the panel with one.

saves him time and lots of money.

Anyhow... Whatever is causing the buzz, I hope you rid yourself from it.

JAson

[JohnnyTooLoud]

Good info above. For more info Rod Gervais posts on power issues (and others) over at http://www.recording.org/cgi-local/ubb/ultimatebb.cgi

Here is on thread called Grounding Mess:
http://www.recording.org/cgi-local/u...;f=34;t=000781

I've seen him post here on occasion but he is very active at recording.org.

---JTL

[spherop]

Thanks for all your helpful posts.

I plugged the pendulum into an outlet that the electrician did not wire - and ... like that - the hum is gone.

So I paid a lot of money for nothing.

What would you do in my place?

Would you demand a refund?

[juniorhifikit]

Originally posted by spherop
Thanks for all your helpful posts.

I plugged the pendulum into an outlet that the electrician did not wire - and ... like that - the hum is gone.

So I paid a lot of money for nothing.

What would you do in my place?

Would you demand a refund?

Just get him to come back and hook the new circuit's ground to the old one - for free. Forget about the new stake he put in the dirt.

[spherop]

Originally posted by juniorhifikit
Just get him to come back and hook the new circuit's ground to the old one - for free. Forget about the new stake he put in the dirt.

I am inclined to go this route - but the fact that I paid for a new stake in the dirt in the first place irks me somewhat - but I suppose it's my bad for letting him tell me it would be a good thing to have.

[JohnnyTooLoud]

If the distance or logistics will allow - have him tie the new ground rod to the main ground at your box. The problem is having two ground points that don't tie together.

When we upgraded the service here we drove two 10 foot rods into the ground. The easier it is for the power to get to ground the better.

If you can't tie the two together then yeah - forget about the new rod and tie the circuit into the main ground.

Good luck and report back what happens.

--JTL

[spherop]

Originally posted by JohnnyTooLoud
If the distance or logistics will allow - have him tie the new ground rod to the main ground at your box. The problem is having two ground points that don't tie together.

When we upgraded the service here we drove two 10 foot rods into the ground. The easier it is for the power to get to ground the better.

If you can't tie the two together then yeah - forget about the new rod and tie the circuit into the main ground.

Good luck and report back what happens.

--JTL

Thanks for all the suggestions and comments.

My electrician did the right thing.
The ground rod was tied in.

The problem was related to a power supply for an LCD monitor - I realized this when hum disappeared every time I turned the monitor off. When I switched power supplies - from an identical monitor - the hum was no longer there.

I also did some tests recording bass and guitar with the pre-amp plugged into the new outlets vs the old outlets and there was less hum and interference with the new. Gratifying to find out the money spent on this grounding job was worth it.

[Jason Poulin]

glad to hear everything is ok!

Jason