When tying a knot solves most of the hum issue!

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
Yup... 120Hz hum even though the amplifier is powered by switching supplies... A simple knot fixed most of it...

Never be afraid to try the cheap solution first LMAO.
 

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I took apart a flat screen TV (scavenger hunt) and saw that the mains power lead was looped once through a ferrite cylinder. I did some internet sleuthing and found out that this was a ground loop breaker scheme for eliminating hum. I took it out and used in my preamplifier.

Does it work? Well there's no hum or ground loops. I've made it a point to grab these out of any flat screen I see in the electronic recycle dumpster. I also saw where Mouser and Digi-Key sell these.
 
I took apart a flat screen TV (scavenger hunt) and saw that the mains power lead was looped once through a ferrite cylinder. I did some internet sleuthing and found out that this was a ground loop breaker scheme for eliminating hum. I took it out and used in my preamplifier.

Does it work? Well there's no hum or ground loops. I've made it a point to grab these out of any flat screen I see in the electronic recycle dumpster. I also saw where Mouser and Digi-Key sell these.


Indeed, ferrite chokes are good for eliminating certain interferences.
I've got a couple of them clipped around various devices around the house.
 
Yup... 120Hz hum even though the amplifier is powered by switching supplies... A simple knot fixed most of it...

Never be afraid to try the cheap solution first LMAO.
Is that cable from a turntable?
Is that green alligator clip jumper your phono ground?

If both are yes, it is proximity between then that reduces ground loop hum.
I wrap my to ground tightly around the tt cables up to the binding post.

Jn
 

kodabmx

Member
Paid Member
2011-10-31 1:00 am
Toronto
Yes, it's a turntable. Yes the green clip is the ground.

I do know there is a lot of stray power interference in here. AM radio is useless, the entire dial is 60/120Hz.

I almost feel like winging common mode toroidal chokes for them or as mentioned, using ferrite. Still, the hum problem is about 95% gone, and it appears to be somewhat inductive. Moving my DAC several feet away further reduced the hum (it has 3 power transformers in it).

I guess it could be RF. An older design would pick up 98.1MHz FM through the turntable cabling. I guess it was a kind of slope detector.
 
Yes, it's a turntable. Yes the green clip is the ground.

I do know there is a lot of stray power interference in here. AM radio is useless, the entire dial is 60/120Hz.

I almost feel like winging common mode toroidal chokes for them or as mentioned, using ferrite. Still, the hum problem is about 95% gone, and it appears to be somewhat inductive. Moving my DAC several feet away further reduced the hum (it has 3 power transformers in it).

I guess it could be RF. An older design would pick up 98.1MHz FM through the turntable cabling. I guess it was a kind of slope detector.
It's just simple loop pickup.
Make a better ground. Take the new ground wire, wrap it tightly the entire way around the shielded pairs, then connect at the preamplifier with minimal loop between it and the RCA's.

Then your equipment should be far more impervious to pickup.

Jn
 
kodabmx said:
I guess it could be RF. An older design would pick up 98.1MHz FM through the turntable cabling. I guess it was a kind of slope detector.
Accidentally picking up broadcast VHF is not too difficult, although also not too difficult to filter it away. What is difficult to do accidentally is to slope detect it. Something in your system must have been resonating near 98.1MHz - maybe a cable?