Hello Forum Members,
I haven't seen this topic posted specific to primary AC wiring.
I am rewiring an ampllifier to improve/reduce noise. I have twisted the AC primary wires and covered them with heatshrink. Is there any downside to covering them with braided copper sleeving before the final PET sleeve is applied? Thank you for your thoughts.
I haven't seen this topic posted specific to primary AC wiring.
I am rewiring an ampllifier to improve/reduce noise. I have twisted the AC primary wires and covered them with heatshrink. Is there any downside to covering them with braided copper sleeving before the final PET sleeve is applied? Thank you for your thoughts.
The transmitted 'noise' or hum picked up in sensitive preamplifiers is due to magnetic flux not RF noise. Heater current etc.
Screening the cable will therefore have no effect because copper braid will not stop the magnetic field.
Mu Metal will work but that is costly and it is more effective to just twist the wires as you have done already.
Screening the cable will therefore have no effect because copper braid will not stop the magnetic field.
Mu Metal will work but that is costly and it is more effective to just twist the wires as you have done already.
Hi JonSnell,
Thanks for your response. I appreciate your input as I am a relative newbie.
Thanks for your response. I appreciate your input as I am a relative newbie.
I bet that most of us can relate to attempting to get some amount of hum eliminated. I just rewired my preamp due to this problem and got lucky that it turned out to be a ground issue in one channel. Generally speaking hum can be reduced when there is the possibility of moving the power transformer away from the affected audio circuit. Don't doubt for a moment that I have tried just about any type of shielding and found that most of my attempts were in vain for blocking a magnetic field. Eventually, I found that mu-metal was best, but not perfect for this problem and it cost quite a bit for a small sheet.
You are wondering about shielding a power line inside of the amp, and I would say that it won't do anything for you even if the small field that the line were to be blocked.
Perhaps if you posted an in focus photo of the area inside of the amp that you want to address, this might be a start. You have the right to own a silent power amp!
You are wondering about shielding a power line inside of the amp, and I would say that it won't do anything for you even if the small field that the line were to be blocked.
Perhaps if you posted an in focus photo of the area inside of the amp that you want to address, this might be a start. You have the right to own a silent power amp!
Hey Ixnay,
Thanks for your detailed reply, I appreciate your time.
I don't have any suitable pics as the amp is torn apart and I plan to rearrange the internal layout. However, your input (along with the other replies) has convinced me that shielding the mains cables is likely a waste of time. The cables will be 4-5" at least from the amplifier boards with the new layout.
I'm probably money ahead to focus on other strategies such as properly twisting AC cables and maintaining distance between power and signal wiring. Not to mention the information I've learned about proper ground wiring since I originally built this amplifier. When I'm done I'll try to remember to post the outcome of my efforts for everyone. Thanks to all for your input!👍
Thanks for your detailed reply, I appreciate your time.
I don't have any suitable pics as the amp is torn apart and I plan to rearrange the internal layout. However, your input (along with the other replies) has convinced me that shielding the mains cables is likely a waste of time. The cables will be 4-5" at least from the amplifier boards with the new layout.
I'm probably money ahead to focus on other strategies such as properly twisting AC cables and maintaining distance between power and signal wiring. Not to mention the information I've learned about proper ground wiring since I originally built this amplifier. When I'm done I'll try to remember to post the outcome of my efforts for everyone. Thanks to all for your input!👍
At the turn of the century, some printers and desk top computers had shielded AC power cords. To reduce their interference emissions, so they could past the required RFI tests.