The No.1 Website for Pro Audio
Electrical Q: A way to isolate? Or give up?
Old 1 week ago | Show parent
  #31
Here for the gear
 

Quote:
Originally Posted by nosebleedaudio View Post
If you have a short run of say 12ga vs a long run of 14Ga there will be a voltage drop difference.Plus the voltage drop you can have thru a cheap 15amp outlet vs a good 20amp..
Have measured this stuff many times..
Good to know.
The car/kitchen outlet is 14 awg from a 15 amp circuit in the main panel to cheap 15 amp outlets. The run is only about 25-30 ft.

The studio is a shorter run from a 20 amp circuit in the subpanel with 12 awg, but the outlets are the same cheap 15 amp.
Old 1 week ago | Show parent
  #32
Lives for gear
 
avare's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
What?
He has a voltage drop of unknown length of 14ga wire between No load & 12 amps..you will have a voltage drop..
Unless IM missing something...
The voltage drop is asymmetrical. Just over half a volt on the neutral and around 1.5 V on the high conductor.
Old 1 week ago | Show parent
  #33
Lives for gear
 
nosebleedaudio's Avatar
Quote:
Originally Posted by avare View Post
The voltage drop is asymmetrical. Just over half a volt on the neutral and around 1.5 V on the high conductor.
There are also unknowns such as a splice in a junction box which will have a voltage drop.. They get warm for a reason..
In fact a cable plugged in the wall outlet with high current will get warm, voltage drop..
We are in the dark here for the most part..
Old 1 week ago | Show parent
  #34
Lives for gear
 
avare's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
There are also unknowns such as a splice in a junction box which will have a voltage drop..
It is not clear where your attitude is coming from. I wrote there is a high resistance in the live conductor. I should have written "live conductor circuit."

There, are you happy?
Old 1 week ago | Show parent
  #35
Lives for gear
 
avare's Avatar
 

Quote:
Originally Posted by nosebleedaudio View Post
In fact a cable plugged in the wall outlet with high current will get warm, voltage drop..
Tell me you are joking. Do you know what I²R loses are? We are not ignoramuses here. Give us some credit.
Old 1 week ago
  #36
Here for the gear
 

Thank you both for weighing in, I know it's difficult when you only have a small piece of the picture, especially with hard for amateurs to read stuff like impedance and voltage spikes on the AC line.

I think it's clear there's some kind of interaction/connection/something between everyone who shares this transformer?

Would an isolation transformer on the studio circuit be a possible solution, or are there other issues that would cause that not to be the answer?
Old 1 week ago | Show parent
  #37
Lives for gear
 

Quote:
Originally Posted by wadesey View Post
Thank you both for weighing in, I know it's difficult when you only have a small piece of the picture, especially with hard for amateurs to read stuff like impedance and voltage spikes on the AC line.

I think it's clear there's some kind of interaction/connection/something between everyone who shares this transformer?

Would an isolation transformer on the studio circuit be a possible solution, or are there other issues that would cause that not to be the answer?
The circuit has high resistance already, so adding an isolation transformer will increase the load.
Old 1 week ago | Show parent
  #38
Here for the gear
 

Quote:
Originally Posted by OpusOfTrolls View Post
The circuit has high resistance already, so adding an isolation transformer will increase the load.
Copy that.

I just checked out the pole and there are more than 7 homes, those wires on the bottom tie go to at least 2 more before the next transformer. And I think they're all split after the transformer, not at it, but I could be wrong...

I guess I'm trying to figure out if there might be more than one problem happening? One or more caused from an interaction between all these homes post-transformer, and more caused from something post-panel.
Old 1 week ago | Show parent
  #39
Lives for gear
 
nosebleedaudio's Avatar
Quote:
Originally Posted by avare View Post
Tell me you are joking. Do you know what I²R loses are? We are not ignoramuses here. Give us some credit.
You didn't mention it, does the OP know about that?
OK, IM done..
Old 1 week ago | Show parent
  #40
Lives for gear
 

Quote:
Originally Posted by wadesey View Post
OK, I was able to get some mostly real numbers, I think...
The car says the current draw is exactly 12A (15A 120V circuit)
Measuring that outlet with no (or almost no) current draw, it's 121.8 V
Under 12A the voltage drops to 118.8, so around 2.5% drop?
The voltage on the neutral with that current draw rises from around .11V to .65V and is inconsistent, it varies between those numbers
So a 3 Volt drop with 12 Amp current.
3/12 =0.25 Ohm source impedance. that's a very good number.

* * * * * * * * *
So get a battery power pre-recorded music source and plug it straight into an amp. Un-plug everything else. Do you still have the problem.

* * * * * * * * * *
what is a 'car' meter?

do the homes have an all metal water pipe system?

What did you measure the Neutral voltage in reference to?
Old 1 week ago | Show parent
  #41
Lives for gear
 

Note: while old neighborhood all metal water pipe systems (used as the outside ground system) can have an impact on the AC power quality, ground rods don't.
Old 1 week ago | Show parent
  #42
Here for the gear
 

Quote:
Originally Posted by Speedskater View Post
So a 3 Volt drop with 12 Amp current.
3/12 =0.25 Ohm source impedance. that's a very good number.

* * * * * * * * *
So get a battery power pre-recorded music source and plug it straight into an amp. Un-plug everything else. Do you still have the problem.

* * * * * * * * * *
what is a 'car' meter?

do the homes have an all metal water pipe system?

What did you measure the Neutral voltage in reference to?
I'll try the battery test, I did a while ago and remember some parts of the problem going away, but possibly still some more noise than "usual" on transducers (guitar pickups and spring reverb only though, not speakers or mics)

Sorry, "car" meter I meant when plugged in the car indicates how much current it's drawing. You can control how much current it draws, but it's only accurate in 1 amp increments and probably not the most accurate way of testing this stuff...

Water pipes are copper in the home, I'm not sure what they are from the municipal supply though. Some houses here still have cast iron I think.

I only measured neutral in reference to ground.
Old 1 week ago | Show parent
  #43
Lives for gear
 
nosebleedaudio's Avatar
Switching supplies (Lighting dimmers) can produce VERY strong Triplen Harmonics on the AC line, strong enough to harm electronic gear..

This is a VERY common problem in clubs where they use the same AC circuit for lighting and Audio..

It would be pretty easy to have a ground rod added to your AC panel, I assume you own the house, NOT renting..

Plus I don't think a simple voltage drop will cause hum ect..

Last edited by nosebleedaudio; 1 week ago at 09:33 PM..
Old 1 week ago
  #44
Here for the gear
 

Our house did have a ground added at some point. There is one old circuit in the house where they didn't connect to it... but everything else is grounded. The stake is visible below the panel.

But, I don't know how many of the neighbors have a ground connection.

They actually gave up on the massive blinking switcher thing, but I'm still trying to figure out if there's some way to isolate from the neighbors since there's clearly some interaction happening.
📝 Reply
Post Reply

Welcome to the Gearslutz Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…
🖨️ Show Printable Version
✉️ Email this Page
🔍 Search thread
🎙️ View mentioned gear
Forum Jump
Forum Jump