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PostPosted: March 25th, 2024, 10:47 am 
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Joined: July 17th, 2016, 6:24 am
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There is a buzz 60Hz buzz in my audio system, which usually gets louder in the nights. Suspecting it to be ground loop hum, got a couple of Balanced Isolation Transformers. There is an improvement in audio, better but 80% of the hum is still present. So got a cheap cable tracer from Amazon. Best $13 I ever spent.

This tracer is picking up hum from the middle of the room, about 8 feet from the nearest wall. As I walk closer to the switches, hum got louder. Turning off the two dimmer switches reduced the hum by about 70%.

Came across this video on YouTube on how the dimmer switches work. Dimmer switches are not stepping down the voltage but are chopping the sinewave.
Holy Crap - How is that even legal?

https://youtu.be/5-wPkFv6eJE?si=wJoTNXoR-mRaKl3t

I have 8 dimmer switches in my home. Going to replace all with regular non-dimming switches before considering a dedicated circuit for the audio room.


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PostPosted: March 25th, 2024, 11:16 am 
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Joined: January 15th, 2015, 7:19 am
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Location: Baltimore MD
great vid, thanks Shashi
Which cable tracer did you buy


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PostPosted: March 25th, 2024, 11:35 am 
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Paul,
This is the tracer.
https://www.amazon.com/dp/B07NHV3Q21?psc=1&ref=ppx_yo2ov_dt_b_product_details


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PostPosted: March 25th, 2024, 12:57 pm 
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Location: Potomac, MD
If you would like to reduce the voltage, a variac is the best solution. Unfortunately they are too large to fit into a wall switch box. The are also pricy.


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PostPosted: March 25th, 2024, 1:13 pm 
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I have dimmers all over the house and not a hint of hum in my speakers. I don't even have balanced lines for the audio signals. How old are your dimmers? Perhaps there has been an improvement in the technology in the past few years.


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PostPosted: March 25th, 2024, 3:01 pm 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
I have 8 dimmer switches in my home. Going to replace all with regular non-dimming switches before considering a dedicated circuit for the audio room.[/quote]

Hey Sashi! I have dimmers though-out and no noise. However, I did find that LED luminairs, depending on the design, have DC power supplies that produce a boat-load of RFI.

You may have another issue but, since I haven't that experience I can't help you. But then -- all of my audio electronics have RFI/EMI Corcom filters on the AC inputs and my equipment, except for my power amps, is plugged into an isolation transformer.

And yes -- Triac-based light dimmers "lie to light source" by chopping the 60-Hz. sine wave delivering a "lower current" to the luminair.

_________________
Walt


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PostPosted: March 25th, 2024, 3:23 pm 
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The older dimmers were the TRIAC style.

The newer LED dimmers are PWM style. The switching frequency should be much higher than 60Hz for PWM dimmers.

The old ones in my house are TRIAC styles. They do make a lot of noise on the AC power line. I used a PS Audio Power Plant 300 and later a Power Plant Premiere (PPP) for the audio system. They both died along with a second PPP. Repair cost was crazy, and still did not work.

Went to GaN Class D Amps with GaN SMPS and no noise even with the old dimmers.


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PostPosted: March 25th, 2024, 4:00 pm 
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If the triac type dimmers are causing you problems with your equipment, the power supplies in those pieces probably have insufficient internal line filtering, you have grounding problems, or you have line to line problems. There are other devices in your house that can generate noise on the line and in addition, noise can come into your house power from the outside. Instead of trying to fix all the power supplies you might want to first get a high quality line filter such as the one below and put it in a metal box with a duplex outlet. Make sure that the ground connection to the box is good and then plug all the devices into this box using high quality power strips if necessary. You should always try to have all equipment connected to one line. This filter has a 15 amp rating but they come in other sizes as well. I have used these types for years and they work well. The power supplies I build for myself have sufficient line noise filtering that nothing on the line gets through.

https://www.mouser.com/ProductDetail/TE ... cKoQ%3D%3D


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PostPosted: March 25th, 2024, 4:07 pm 
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Joined: July 8th, 2016, 4:34 pm
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Also if you are powering your equipment from different AC circuits you should use a star ground to avoid ground loops. All grounds should go to the ground on one outlet.


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PostPosted: March 25th, 2024, 4:20 pm 
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Joined: July 17th, 2016, 6:24 am
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tomp wrote:
If the triac type dimmers are causing you problems with your equipment, the power supplies in those pieces probably have insufficient internal line filtering, you have grounding problems, or you have line to line problems. There are other devices in your house that can generate noise on the line and in addition, noise can come into your house power from the outside. Instead of trying to fix all the power supplies you might want to first get a high quality line filter such as the one below and put it in a metal box with a duplex outlet. Make sure that the ground connection to the box is good and then plug all the devices into this box using high quality power strips if necessary. You should always try to have all equipment connected to one line. This filter has a 15 amp rating but they come in other sizes as well. I have used these types for years and they work well. The power supplies I build for myself have sufficient line noise filtering that nothing on the line gets through.

https://www.mouser.com/ProductDetail/TE ... cKoQ%3D%3D


Tom,

I installed a balanced isolation transformer which did not help much. 60Hz hum is still coming thru. But, when I switch off the dimmers, level of hum goes down.


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