Need Advice on How to Eliminate Low Level Hum from Transformer inside a CD Player

[Haflermichi]

He has already stated at least twice he's not going to replace it.

 

[Chrispy]

He has already stated at least twice he's not going to replace it.

Thanks, glancing thru didn't see that. I saw relatively cheap then buying extra gear to make it work, which didn't make much sense.

 

[Haflermichi]

Thanks, glancing thru didn't see that. I saw relatively cheap then buying extra gear to make it work, which didn't make much sense.

Absolutely agree with you there. Throwing good money after bad does not make sense.
$2 worth of rubber may be all that is needed.

 

[Chrispy]

Absolutely agree with you there. Throwing good money after bad does not make sense.
$2 worth of rubber may be all that is needed.

Agree, especially if it only plays cds.

 

[tmtomh]

If it's mechanical hum - and it appears to be - then it's almost certainly DC in the AC line. DC blockers work, and isolation transformers work. And you're not going to find one for less than $120-150. It makes little sense to spend that when the CD player, while a nice unit, is worth about the same amount of money. But a DC blocker or Isolation transformer should do the trick.

Still the same price range, but for what it's worth I have this model:

HumDinger DC Line Blocker

What the HumDinger will do: Block low-level DC voltage sitting on your AC power line that causes the power transformer to hum or buzz. This type of mechanical transformer hum may be caused if other devices on your power line, or devices on nearby power lines, use AC power asymmetrically. This...

avahifi.com

I don't need it anymore, but when I did need it, it worked great.

 

[antcollinet]

Another suggestion is damping material under the player - the vibrations may well transfer to whatever flat surface it is on and use that as a sound board.



Then there is another approach you could take.

Can you hear it when listening to music at your normal listening position? If not, forget about it - it doesn't matter. There are all sorts of sounds I can hear right now with no music playing. Light traffic noise, heating system noises. Other people doing stuff in the house. Very slight hum from the fridge two rooms way. None of it is even a slight problem when the music is playing.

 

[Zapper]

If it's mechanical hum - and it appears to be - then it's almost certainly DC in the AC line. DC blockers work, and isolation transformers work. And you're not going to find one for less than $120-150. It makes little sense to spend that when the CD player, while a nice unit, is worth about the same amount of money. But a DC blocker or Isolation transformer should do the trick.

Still the same price range, but for what it's worth I have this model:

HumDinger DC Line Blocker

What the HumDinger will do: Block low-level DC voltage sitting on your AC power line that causes the power transformer to hum or buzz. This type of mechanical transformer hum may be caused if other devices on your power line, or devices on nearby power lines, use AC power asymmetrically. This...

avahifi.com

I don't need it anymore, but when I did need it, it worked great.

It's not "almost certainly" DC on the line, although that is one possibility. There are other possibilities. The HumDinger description states that it cannot stop hum from a defective power transformer:

Cure hum caused by a defective noisy power transformer. If the transformer has a loose core that hums the HumDinger may reduce the hum slightly, but will not eliminate it.

Loose cores or laminations are a relatively common problem with cheap transformers.

In comment #31 Dimitri posted a video of a very badly buzzing transformer due to loose laminations.

If there is DC on the line then other transformer powered gadgets should also buzz. Do they?

DC is a problem primarily for toroid transformers, as previous discussions on this thread indicate. EI core transformers like this one have a gap between the E and I piece that greatly suppresses saturation from small DC biases. Toroids have no gap, hence saturate much more easily in the presence of DC.

 

[tmtomh]

It's not "almost certainly" DC on the line, although that is one possibility. There are other possibilities. The HumDinger description states that it cannot stop hum from a defective power transformer:

Loose cores or laminations are a relatively common problem with cheap transformers.

In comment #31 Dimitri posted a video of a very badly buzzing transformer due to loose laminations.

If there is DC on the line then other transformer powered gadgets should also buzz. Do they?

DC is a problem primarily for toroid transformers, as previous discussions on this thread indicate. EI core transformers like this one have a gap between the E and I piece that greatly suppresses saturation from small DC biases. Toroids have no gap, hence saturate much more easily in the presence of DC.

I understand that toroidals are more commonly affected by DC in the AC line - but EI core transformers can still hum from that cause as well. I also agree that it could just be the transformer and it needs to be potted or replaced.

The fact that other transformer-powered devices in the OP's home, or even in the same circuit, do not buzz tells us exactly nothing about the cause. I've had multiple toroid-based devices connected to the same AC outlet and one has mechanically buzzed while the other has not. And I'm sure I'm not alone in that experience.

 

[Zapper]

IThe fact that other transformer-powered devices in the OP's home, or even in the same circuit, do not buzz tells us exactly nothing about the cause.

True. But if other transformers DID buzz it would lend support the DC hypothesis.

 

[Wooferhead]

Was the table bare or was there a tablecloth ?

The table was bare. Does it make any difference?

 

[Wooferhead]

How do you think those of us with the skills got them? 95% of the time it's because we grabbed a screwdriver and started tampering. Even those of us with formal technical education developed our tampering skills by just doing it. They don't really teach tampering in school. Nothing tampered, nothing gained!

Perhaps I should grab a cheap old used unit to practice. Don't think I want to start with my current one.

 

[Wooferhead]

Does the player make the physical hum when turned on, but with the lid is removed? Often, transformers placed in that orientation will induce hum in the light gauge outer casework/lid.

I begin to think that the hum is caused by the vibration to the entire bottom panel of the case.

 

[Wooferhead]

If you have the skill to remove the lid, assuming you took those pictures, you have the skill to try putting soft, thin rubber underneath the 4 Phillips head screws that appear to be holding the transformer to the chassis.
Just PLEASE make sure the unit is unplugged from the wall, not just turned off.
A good hardware store should have sheet or strips of rubber of varying thickness. You don't need much, a few inches at most. Just enough to float the mounting tabs of the transformer. Don't crank the mounting screws back down tightly. The idea is to "float" the transformer via the compliance of the rubber.
I would try that first before spending any more money on devices.

Sounds like a good idea.

 

[Wooferhead]

Rather than buy extra gear, why not just replace the player?

The player is relatively new.

 

[JayGilb]

Can your hear the hum from your usual listening position ?

 

[Wooferhead]

True. But if other transformers DID buzz it would lend support the DC hypothesis.

There is no hum or buzz in the receiver connected to the CD player.

 

[Wooferhead]

Can your hear the hum from your usual listening position ?

Without music when the room is quiet, yes. But it is a very low level hum.

 

[Wooferhead]

If it's mechanical hum - and it appears to be - then it's almost certainly DC in the AC line. DC blockers work, and isolation transformers work. And you're not going to find one for less than $120-150. It makes little sense to spend that when the CD player, while a nice unit, is worth about the same amount of money. But a DC blocker or Isolation transformer should do the trick.

Still the same price range, but for what it's worth I have this model:

HumDinger DC Line Blocker

What the HumDinger will do: Block low-level DC voltage sitting on your AC power line that causes the power transformer to hum or buzz. This type of mechanical transformer hum may be caused if other devices on your power line, or devices on nearby power lines, use AC power asymmetrically. This...

avahifi.com

I don't need it anymore, but when I did need it, it worked great.

Thanks for the suggestion. Didn't expect DC blockers and isolation transformers to be that pricey.

 

[JayGilb]

Without music when the room is quiet, yes. But it is a very low level hum.

I would do what @Haflermichi suggested and use some rubber washers between the transformer mounting screws and the case.

 

[Wooferhead]

Another suggestion is damping material under the player - the vibrations may well transfer to whatever flat surface it is on and use that as a sound board.



Then there is another approach you could take.

Can you hear it when listening to music at your normal listening position? If not, forget about it - it doesn't matter. There are all sorts of sounds I can hear right now with no music playing. Light traffic noise, heating system noises. Other people doing stuff in the house. Very slight hum from the fridge two rooms way. None of it is even a slight problem when the music is playing.

I think you are on to something here.

No, I can't hear it when the music is on.