Electrician Talk banner

21 - 31 of 31 Posts

·
professional redneck
Joined
·
119 Posts
new powered PA espacialy mackie jbl and yorkville draw ridiculisly low amount of curent, i'm thinking your problem might be comming from a ground loop, do the audio input of your pa have a ground lift switch ? something inside may be leaking thru the xlr shield
 

·
Registered
Joined
·
4,665 Posts
......................
OK....the new subs and mains blasting The Stones "Doom and Gloom" mp3 at dangerous levels wavers from 1.7 to 2 amps.

The set of 1530's (no subs)on the 9 amp/15 amp (professionally installed BR) circuit also only went up not even one amp when cranked up as loud as I could get it without hurting or breaking something.

.........................

I think there must be a new design technology with new powered amps. We didn't have them in the olden days and I remember tripping breakers all the time.

I just looked at a decibel chart. Pain begins at 125db. The loudest sound possible is 194db. I'm going to get a decibel meter. I'm guessing we play in the studio in the 90-95 range.
What meter are you using for your measurements? Does it have a peak hold function? Remember that even tame audio has peaks happening in very fast time, in hundreds or thousands of cycles. Most amp meters cannot respond (or display) that fast. Only a data logger will be able to capture those peaks, if it even is capable of that.

That said, you are correct, most new amplifiers have new "switch-mode" power supplies and are extremely efficient compared to the old ones. That does make a difference in how they draw from the AC mains.

The best decibel meter for the money is hands down the digital one from Radio Shack... very accurate and rugged.

http://www.radioshack.com/digital-sound-level-meter/3300099.html#.VMP54y7HnAk

And only $30.00

(This is a newer design so I can't vouch for how rugged this one would be, the new case on it look cheesy compared to the older black-cased ones.)

Still a great value and idea for any musician/audio guy. :thumbup:
 

·
Registered
Joined
·
7,789 Posts
Discussion Starter #23
i'm thinking your problem might be comming from a ground loop, do the audio input of your pa have a ground lift switch ? something inside may be leaking thru the xlr shield
No lift switches anywhere. I disconnected the xlr's to rule them out.

It must be some of that crazy crap discussed on page one which would require an isolation transformer, which I barely understand, or a choke, which I understand even less :laughing:



What meter are you using for your measurements?
My Fluke T5-600
 

·
professional redneck
Joined
·
119 Posts
It must be some of that crazy crap discussed on page one which would require an isolation transformer, which I barely understand, or a choke, which I understand even less :laughing:
a ferrite choke is just some piece of iron in wich power cord pass or make a loop thru http://en.wikipedia.org/wiki/Ferrite_bead

you can often find them in old cathode ray tube monitor and inside computer psu

http://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers

they work by the higher inductance of the higher frequency of the noise that the cable carry.

they dissipate noise in the magnetic core, it's what is call eddy current in english i think
 

·
Registered
Joined
·
7,789 Posts
Discussion Starter #25
Thanks. I did research and read a lot but, some things don't quite register in my brain.

Remember, you are dealing with a trench/conduit/wire/drummer. If something goes in one end and comes out the other, I can generally understand it.:thumbsup:
 

·
Registered
Joined
·
2,967 Posts
Thanks. I did research and read a lot but, some things don't quite register in my brain.

Remember, you are dealing with a drummer. If something goes in one end and comes out the other, I can generally understand it.:thumbsup:
AH!
A drummer ?
That explains a lot !
:thumbsup:

View attachment 45649

We understand that it is a technically compex subject
And that you might not fully understand it
But as someone who does understand it ( geek ) :eek:
I really think that a 1 to 1 power isolation transformer will
help your problem.
 

·
Registered
Joined
·
7,789 Posts
Discussion Starter #27
I really think that a 1 to 1 power isolation transformer will
help your problem.
I started searching for an inexpensive transformer to mount it in a box with a cord and 4 plex. That's when I realized that the more amperage = more money and size/weight. A full 20A unit was over $300.

That's when I put the amp meter into play to decide how much amperage I really need.
 

·
professional redneck
Joined
·
119 Posts
I started searching for an inexpensive transformer to mount it in a box with a cord and 4 plex. That's when I realized that the more amperage = more money and size/weight. A full 20A unit was over $300.

That's when I put the amp meter into play to decide how much amperage I really need.
or you just filter it with an inexpensive/lightweight choke to test first if there is some kind of progress
 

·
professional redneck
Joined
·
119 Posts
Yes exactly this try it on an extension cord that will supply your 4 speaker so you'll only have to buy one of those. You can also find them for free inside descktop computer power supply.
 
21 - 31 of 31 Posts
Top