Can AC wires induce hum in output transformers?

Rob11966 · 26th March 2009, 10:24 AM

Hi folks,

Can twisted AC wires (HV or heater) induce hum in (quality) transformers if they run close to the transformer? If so, how close is too close? I am not talking about the proximity or orientation of the power transformer to the output transformer but rather the AC secondary leads.

As a supplementary question, if induced hum is possible, would a 2mm aluminum plate between wires and transformer act as a shield?

Obviously, the simple solution is to keep the two separate but for various irritating reasons this is not easily possible with my current chassis.

Any input welcome. Thanks in advance.

Rob

analog_sa · 26th March 2009, 10:37 AM

This induction is definitely not an issue at output levels. And the 2mm alu will have practically no effect.

Jeb-D. · 26th March 2009, 04:50 PM

I'd only worry about it if the transformer is an open bracket interstage transformer that is being used in low level circuitry.

The twisted pair should be pretty resistant against causing this sort of thing.

Wavebourn · 26th March 2009, 05:06 PM

No.

Richard Ellis · 26th March 2009, 05:15 PM

First off...Aluminum is a non-magnetic metal and will not "short out" a stray unwanted magnetic field.
If I recall, Morgan Jones made a notation to twist-per-inch of such lines. The twisting has a nulling effect for magnetic fields.
It would be a nice study of twisting 'rates' vs. field 'output'????
Seeing how some run these lines, I have the impression a "flanking manouver" with twisted pairs is a viable wiring technique.
Rather...not trying to do a shortest possible but a sweeping route thru the chassis...trying to maintain the longest distance between other wires. This of course will look kinda kooky with the twisted pairs floating thru the chassis toward their target.
I have the impression fields generated by twisted pairs is measured in millimeters. EG..3-7mm
_______________________________________________Ric k........

Rob11966 · 26th March 2009, 07:56 PM

Thanks for the replies,

Normally I run all of the AC power lines away from any of the signal path, including the output transformers. Unfortunately the penetratrators for my power transformer leads ended up very close to my output transformer as I was forced to move my output transformers due to a problem with the original design of the chassis.

Anyhow, this is good news.

Cheers and thanks again.

Rob

pointy · 26th March 2009, 11:18 PM

it could be that the transfromers are acting on the ac wires. if so screen them.................................i think ?

26th March 2009, 10:24 AM	#1
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	Can AC wires induce hum in output transformers? Hi folks, Can twisted AC wires (HV or heater) induce hum in (quality) transformers if they run close to the transformer? If so, how close is too close? I am not talking about the proximity or orientation of the power transformer to the output transformer but rather the AC secondary leads. As a supplementary question, if induced hum is possible, would a 2mm aluminum plate between wires and transformer act as a shield? Obviously, the simple solution is to keep the two separate but for various irritating reasons this is not easily possible with my current chassis. Any input welcome. Thanks in advance. Rob

26th March 2009, 05:06 PM	#4
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	No. __________________ If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Difference between SE output transformer and push-pull output transformers	hilbert_mostert	Tubes / Valves	12	8th March 2009 05:10 PM
Help identifying a pair of output transformers and power transformers	mjk130	Parts	3	30th January 2009 10:44 AM
Ferrite bed od the wires who goes to output transistors ?	gaetan8888	Solid State	5	21st June 2007 06:50 PM
Conductors (I.C.'s, RCAs, internal wires, speaker wires)	bigphil	Parts	1	25th November 2005 06:47 PM
wires of output transformer are too thin!	zxx123	Tubes / Valves	5	4th February 2005 10:18 AM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

26th March 2009, 10:37 AM	#2
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	This induction is definitely not an issue at output levels. And the 2mm alu will have practically no effect.

26th March 2009, 04:50 PM	#3
Jeb-D. diyAudio Member Join Date: Nov 2005 Location: SoCal	I'd only worry about it if the transformer is an open bracket interstage transformer that is being used in low level circuitry. The twisted pair should be pretty resistant against causing this sort of thing.

26th March 2009, 05:15 PM	#5
Richard Ellis diyAudio Member Join Date: Sep 2006 Location: Mar del Plata, a BIG seasonal getaway city, can see the Ocean from our residence.	First off...Aluminum is a non-magnetic metal and will not "short out" a stray unwanted magnetic field. If I recall, Morgan Jones made a notation to twist-per-inch of such lines. The twisting has a nulling effect for magnetic fields. It would be a nice study of twisting 'rates' vs. field 'output'???? Seeing how some run these lines, I have the impression a "flanking manouver" with twisted pairs is a viable wiring technique. Rather...not trying to do a shortest possible but a sweeping route thru the chassis...trying to maintain the longest distance between other wires. This of course will look kinda kooky with the twisted pairs floating thru the chassis toward their target. I have the impression fields generated by twisted pairs is measured in millimeters. EG..3-7mm _______________________________________________Ric k........

26th March 2009, 07:56 PM	#6
Rob11966 diyAudio Member Join Date: Jun 2007 Location: Australia	Thanks for the replies, Normally I run all of the AC power lines away from any of the signal path, including the output transformers. Unfortunately the penetratrators for my power transformer leads ended up very close to my output transformer as I was forced to move my output transformers due to a problem with the original design of the chassis. Anyhow, this is good news. Cheers and thanks again. Rob

26th March 2009, 11:18 PM	#7
pointy diyAudio Member Join Date: Mar 2009	it could be that the transfromers are acting on the ac wires. if so screen them.................................i think ?