Grounding

A

ADATlove

New member
I have been using a modern Behringer mixer, which is grounded, and every 20 mnutes or so I experience a power surge which is probably caused by the AC kicking in. I just swapped the Behringer out for a Tascam M320B, which is not grounded, and the surges that used to result only in a slightly dimmed light and an indication on my power conditioner, now give me a pretty bad hum. I tried a few things to narrow the problem and it appears as though the hum only comes through the main L/R bus. So when I'm in the "hum period" and I switch into solo mode I get no hum.

What can I do to fix this? Is it a grounding issue or am I barking up the wrong tree entirely? Can I merely install a new power cord that is grounded by just touching the ground wire to the Tascam's metal chasis?

Thanks for your help!
 
ADATlove said:
I have been using a modern Behringer mixer, which is grounded, and every 20 mnutes or so I experience a power surge which is probably caused by the AC kicking in.
Click to expand...
That would not be a surge. Voltage drop caused by the inrush on the compressor unit (AC).
I just swapped the Behringer out for a Tascam M320B, which is not grounded, and the surges that used to result only in a slightly dimmed light and an indication on my power conditioner, now give me a pretty bad hum. I tried a few things to narrow the problem and it appears as though the hum only comes through the main L/R bus. So when I'm in the "hum period" and I switch into solo mode I get no hum.

What can I do to fix this? Is it a grounding issue or am I barking up the wrong tree entirely? Can I merely install a new power cord that is grounded by just touching the ground wire to the Tascam's metal chasis?

Thanks for your help!
Click to expand...

What indicator are you getting on your conditioner? What kind is it? First off confirm it's the AC causing the hum. Double check that closely. Is it only when the AC kicks on or while it's running the whole time? If you can confirm this then the next job is to check how it and your rig is powered. I'll assume you have circuit breakers. If this is a 240V AC we have other issues. If it's 120V, then make sure it's not on the same leg powering your rig. If it is, either have an electrician or someone comfortable with panel boards move it to the other leg.

Moving on. 240V AC system. Again if you've confirmed the AC is doing this (while it's running), it's possible the windings in the compressor might be leaking to ground a bit. This happens when motors get old. This could get 60 cycles returned to ground on your elec panel and thus show up in your audio's power circuit. I really don't think you have a grounding issue here. Yes it was quieter with the other mixer but it still existed. My guess is voltage drop if it's just on start up of the AC.

Back to in-rush. Do you know anyone with UPS? A decent one will take care of voltage drops to a point and if that's the real problem, it'd be worth checking out. See if you can borrow one but check the wattage ratings on all your gear and compare to the wattage rating on the UPS.

Hope this helped a little bit and good luck.
 
Thanks for the info. It happens when the AC kicks in, the meter on my power conditioner drops from about 114 to 100. It's a Furman power conditioner, the model with the lights (which don't dim anymore) and the meter. The hum only happens when the AC kicks in but hums have been much more audible since I swapped mixing desks. I'm going to try shutting off the AC tomorrow to test that. Then I'll try to make sense of the electrical issue, but I am not experienced on that end so it's going to mean contacting an electrician for sure.

What is a UPS? Some sort of voltage meter?

Thanks again!
 
UPS is uninteruptable power supply. Used for computers alot. The good ones will handle a surge or maintain voltage during a drop. Some have conditioning circuits as well.

If your meter is accurate, you have a voltage problem. 100V is not a good operating voltage for most things. I'm curious what the voltage is at your service. Are you in a major city? 114V is on the low side with no big loads. Could be your panel needs to be balanced. This can be checked by an electrian and isn't a big deal.

Normally the lowest we like to see is 116V per leg at the service.
Let me know how it goes.
 
if you have any equipment worth any money.. you should really have a UPS to power it..
a quick $120 investment is well worth the protection to your hundered or thousands of dollars worth of audio equipment
 
ADATlove said:
Can I merely install a new power cord that is grounded by just touching the ground wire to the Tascam's metal chasis?
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ADAT,

I noticed no one answered this part of your question - so I will.

DO NOT DO THAT !!!!!!!!!!!!!!

Any equipment that is not provided with a ground plug is designed that way for a reason -

The lack of a ground plug indicates that a product is "double grounded" - which means that the method of protecting human life and limb is done by seperating the chassis from the outside of the product.

Adding a seperate ground to the chassis can destroy the equipment (by providing a power path where it is not supposed to exist - as well as potentially (depending on how exactly it was done) producing a electrical path that could be harmful to the people operating the gear.

BTW - just for the record - I agree that this does not sound like a grounding problem - in fact it doesn't sound like a real big deal - just a power drop when the compressor comes on - the UPS is the best way to go - will do a lot to protect your gear investment as well.

If your problem was a grounding issue - you would have a constant (dirty) 60 cycle signal coming through your gear....... ground loops are caused by multiple paths to ground with the same power.......

Sincerely,

Rod
 
Alright, I will look into a UPS...any recommendations? I'll also have an electrician check it out in case there's something else I can do for a long-term fix.

Thanks again.
 
Put the A/C unit on a dedicated circuit, sounds like its drawing power from the desk supply, not good especialy if a computer is on the same circuit, an initial A/C compressor surge can draw as much as 15/20 amps depending on BTU's.
 
Rod Gervais said:
ADAT,

I noticed no one answered this part of your question - so I will.

DO NOT DO THAT !!!!!!!!!!!!!!

Sincerely,

Rod
Click to expand...

Glad you caught that Rod! Crossed my mind in my responses but lost it in translation. Very important point!
 
So it looks like I have two (possibly related) problems. First of all, my house is sucking so much power this summer that the juice I'm getting in my "control room" is dangerously low. Secondly, I get that hum when the AC kicks in because it drops even further. But why is there only hum on the stereo bus and not when I engage solo mode on a channel or two?

Also, I do not run a computer in my setup at all. It's just a pair of ADATs, my board, and a bunch of rack gear. Not sure if that changes anything.

Now I'm a bit confused about what to do first? Should I contact an electrician and get halp pushing things onto different circuits so nothing's pulling too much on one? Or should I get a UPS and call it a day? I feel like I should have the house checked out before I do anything. The UPS is just backup protection, right?

Thanks!
 
I would suggest contacting an electrician. A UPS will serve the purpose for which it's intended (back up and some will/do clean up the AC source) but, they won't correct a phase load imbalance if that is what your problem is. Not to scare you but, I have seen voltage drops due to loose mechanical connections in electrical panels. The high resistance in front of a large load device like an AC unit can eventually heat the loose connection and fail...or worse.

In my mind, you've already answered your question with a question...you've got a couple things going on, you're concerned and things aren't working as they should. You don't have that much gear...it alone shouldn't be enough to bring your circuits down like that. Sounds to me as though there have been some past "home improvements" made which may or may not have been done by code or you've simply maxed the services out. Play it safe and just have a simple inspection done.

Peace my brutha ;)
 
punkin said:
I would suggest contacting an electrician. A UPS will serve the purpose for which it's intended (back up and some will/do clean up the AC source) but, they won't correct a phase load imbalance if that is what your problem is. Not to scare you but, I have seen voltage drops due to loose mechanical connections in electrical panels. The high resistance in front of a large load device like an AC unit can eventually heat the loose connection and fail...or worse.

In my mind, you've already answered your question with a question...you've got a couple things going on, you're concerned and things aren't working as they should. You don't have that much gear...it alone shouldn't be enough to bring your circuits down like that. Sounds to me as though there have been some past "home improvements" made which may or may not have been done by code or you've simply maxed the services out. Play it safe and just have a simple inspection done.

Peace my brutha ;)
Click to expand...
Ditto! I'm an electrician but you're out of my service area I'm guessing. get it checked out. You won't retgret it, you'll learn something, and sleep a little better. I'm betting for a little money you'll take care of the problem and learn some valuable electrical theory while you're at it.
 
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