subwoofer isolation transformer possible hum reducer...?

B

Boston Chris

Audiophyte
Given that the powered subwoofer hum requires RCA connection with the amplifier, and powering both the subwoofer and the integrated amplifier from the same multiple outlet, heavy duty extension cord has no effect on the hum, is a subwoofer isolation transformer still a possibility for hum reduction/elimination?

Details: 60Hz or 120Hz hum in Klipsch 10-SW powered subwoofer connected to Line Magnetic 210IA integrated amplifier (no external preamp in system)

Power cord on subwoofer is: (1) two pronged at male end and (2) hardwired at subwoofer end.

Thank you!

Hum frequency
Could be piano B2 (~ 120 Hz) or
Piano B1 (~60 Hz) –
very hard to discriminate​
With no subwoofer RCA input​
No hum
Add subwoofer RCA input from Line Magnetic amplifier​
hum​
Change Line Magnetic
Amplifier volume setting​
No effect on hum​
Change Line Magnetic
amplifier source selector​
No effect on hum​
Disconnect all Line Magnetic
amplifier RCA inputs​
No effect on hum​
Power Line Magnetic amplifier and subwoofer amplifier into
same extension cord​
No effect on hum​
Multiple Repositioning:
amplifier to subwoofer RCA interconnects position with respect to all power chords​
No effect on hum​
Change amplifier to subwoofer
RCA interconnect cables​
No effect on hum​
 
clubfoot

clubfoot

Audiophyte
Is the Line Magnetic Amplifier connected to the wall power outlet with a three pronged power cable connector?
 
B

Boston Chris

Audiophyte
Yes, Line Magnetic Amplifier connected to the wall power outlet with a three pronged power cable connector. Thanks!
 
B

Boston Chris

Audiophyte
If you can try a "cheater" plug/adapter,.... three pronged to two pronged. From the details you gave it looks like it is your LMA is producing the hum.
Something like this:
Thank you for the idea: I tried a cheater plug on the Line Magnetic amplifier power cord in every possible combination with the subwoofer power cord - Both in multi-outlet extension cord, both in same wall socket, in different wall sockets, etc. Alas, no reduction in hum.

A question: Does the fact that the hum persists when both subwoofer and Line Magnetic amp are plugged into the same multi-outlet extension cord mean the hum is not from a ground loop? Thank you!
 
TLS Guy

TLS Guy

Audioholic Slumlord
Given that the powered subwoofer hum requires RCA connection with the amplifier, and powering both the subwoofer and the integrated amplifier from the same multiple outlet, heavy duty extension cord has no effect on the hum, is a subwoofer isolation transformer still a possibility for hum reduction/elimination?

Details: 60Hz or 120Hz hum in Klipsch 10-SW powered subwoofer connected to Line Magnetic 210IA integrated amplifier (no external preamp in system)

Power cord on subwoofer is: (1) two pronged at male end and (2) hardwired at subwoofer end.

Thank you!


Hum frequency​
Could be piano B2 (~ 120 Hz) or
Piano B1 (~60 Hz) –
very hard to discriminate​
With no subwoofer RCA input​
No hum​
Add subwoofer RCA input from Line Magnetic amplifier​
hum​
Change Line Magnetic
Amplifier volume setting​
No effect on hum​
Change Line Magnetic
amplifier source selector​
No effect on hum​
Disconnect all Line Magnetic
amplifier RCA inputs​
No effect on hum​
Power Line Magnetic amplifier and subwoofer amplifier into
same extension cord​
No effect on hum​
Multiple Repositioning:
amplifier to subwoofer RCA interconnects position with respect to all power chords​
No effect on hum​
Change amplifier to subwoofer
RCA interconnect cables​
No effect on hum​
So your sub is NOT the cause of the hum. Since you still have hum with all inputs disconnected, I can tell you for sure, that your Change Line Magnetic amplifier is faulty, and sending hum to the subwoofer. From what you posted, that is the only conclusion possible. This is not a ground loop.
 
B

Boston Chris

Audiophyte
So your sub is NOT the cause of the hum. Since you still have hum with all inputs disconnected, I can tell you for sure, that your Change Line Magnetic amplifier is faulty, and sending hum to the subwoofer. From what you posted, that is the only conclusion possible. This is not a ground loop.
Well, to be fair, I can only (barely) hear the hum when the subwoofer amplifier is turned up all the way, there is no input into Line Magnetic amp, and I’m kneeling with my ear 6 inches from the subwoofer driver.

So maybe I’ll just stop doing that, stop looking for any ground loops, and listen to some music. . Thanks so much for your help!
 
TLS Guy

TLS Guy

Audioholic Slumlord
Well, to be fair, I can only (barely) hear the hum when the subwoofer amplifier is turned up all the way, there is no input into Line Magnetic amp, and I’m kneeling with my ear 6 inches from the subwoofer driver.

So maybe I’ll just stop doing that, stop looking for any ground loops, and listen to some music. . Thanks so much for your help!
Well, that was certainly not something to make a fuss over. That would be a worst case for signal to noise ratio and expected behaviour.

So what you should do is set the sub volume half way and go from there, by increasing the output from the amp, until the volume is correct. That will optimize the signal to noise ratio.
 
lovinthehd

lovinthehd

Audioholic Jedi
Yes, what is the reason for full gain on the sub amp? Is the pre-out level so low?
 
TLS Guy

TLS Guy

Audioholic Slumlord
Yes, Line Magnetic Amplifier connected to the wall power outlet with a three pronged power cable connector. Thanks!
I have just looked up that amp. You must have money to burn. Let me give it to you straight. That amp is a single ended tube amp abortion. That is just a plain dumb purchase and audiophoolery of extreme proportions. That is a crude amp, however fancy the cosmetics, and just an absolute con. In addition it has no subwoofer output, and certainly no bass management. Anyone who falls for this sort of nonsense is in severe need of remedial education.
 

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