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DC filter / blocker? Experiencing transformer hum

H

Hcanning

pfm Member
Hi all,

I hear an occasional hum/buzz from the transformer in my Meridian 557. It isn't constant, only perodical, and so I have deduced that some sort of floating DC on the mains is to blame. At the same time, I can hear a hum from the amplifier of a subwoofer located in a different room of the house.

this filter seems to fit the bill perfectly, however it's only rated for 1.2kva where my Meridian supposedly sports a 1.6kva transformer.

Will this be a problem considering I'm never likely to draw anywhere near enough peak current, or are transients likely to reach this?

If yes, has anyone found any comparable filters that can handle more current? I seemingly can't find anything else online that isn't a 'consumer' mains filter costing a few hundred, or mains leads costing thousands (!!)


Thank you :)
 
Yeesh, I don't really want to spend that much, I must admit! Is that my only option?

I suppose my next question is, is the hum/buzzing of the transformers going to cause any lasting damage?! It's pretty intermittent.


Thanks!
 
My G57 was doing exactly the same thing: the hum would appear at a very low level, gradually increase in volume (although still barely audible from across the room) then subside and disappear - a moment's silence and the cycle would repeat. The amp then ceased to work at all, and I'm waiting to find out whether the two are connected (and how much it's going to cost....).
I'd expect amps at this level to have their own built-in mains filters, and given their age, component failure must be a possibility. So it may be worth having a word with Meridian before addressing the mains supply itself (despite the Sub noise - is it constant, and does either oscillate as mine did?)
 
davidjt said:
My G57 was doing exactly the same thing: the hum would appear at a very low level, gradually increase in volume (although still barely audible from across the room) then subside and disappear - a moment's silence and the cycle would repeat. The amp then ceased to work at all, and I'm waiting to find out whether the two are connected (and how much it's going to cost....).
I'd expect amps at this level to have their own built-in mains filters, and given their age, component failure must be a possibility. So it may be worth having a word with Meridian before addressing the mains supply itself (despite the Sub noise - is it constant, and does either oscillate as mine did?)
Click to expand...

What do you mean by this? Does the power light come on? If not check the fuse in the back of the amp. There is a drawer and should have a spare so you can swap them over. They do age and eventually blow. This happened to one of my 559s.

Cheers,

DV
 
Hcanning said:
Yeesh, I don't really want to spend that much, I must admit! Is that my only option?

I suppose my next question is, is the hum/buzzing of the transformers going to cause any lasting damage?! It's pretty intermittent.


Thanks!
Click to expand...

.....and that is at the cheaper end. Once you get to such large toroidal transformers hum/buzzing is more likely due to their low winding resistance. Also to block DC on such devices safely will be expensive.

Your xformer is protected by the fuse in the drawer on the rear of the amp. My 559s each have two 1.2KA transformers so thats a total 2.4KVA yet the fuse is a T5A. Yours may be the same or maybe smaller say T3.5A.

Cheers,

DV
 
There is no possibility of damage. My advice would be ignore it if you can. They are not particularly difficult to DIY if you can solder OK etc but we are talking 240V here so don't do it unless you are confident!
 
Thank you both. That's reassuring.

It's far less regular to hear the humming than it is to be in complete silence, and so it doesn't bother me really. I was only interested to see if anything was required to prevent equipment damage.

:)
 
Darth Vader said:
What do you mean by this? Does the power light come on?



DV
Click to expand...

The stand-by light illuminated when switching on at the back, but several attempts to power on from there (with various mains leads) resulted in a relay click and shut-down. Fuse was fine. I suspect a fault in the psu and the protection circuitry simply doing its job.
 
davidjt said:
The stand-by light illuminated when switching on at the back, but several attempts to power on from there (with various mains leads) resulted in a relay click and shut-down. Fuse was fine. I suspect a fault in the psu and the protection circuitry simply doing its job.
Click to expand...

Have you tried removing all inputs? If so then it looks like service time at the Merdian Repair Shop.

http://www.pinkfishmedia.net/forum/showthread.php?t=124364&highlight=meridian+service

also on t'web

http://meridianrepairshop.co.uk/?page_id=10

They have quite a few jobs on their Q so best contact asap.

Cheers,

DV
 
DV
Yes, first thing I did was to disconnect everything.
As the G57 weighs in at 24Kg, carriage/convenience is an issue.

Anyway, thanks for the tip and I'll give MRS a ring.
 
davidjt said:
DV
Yes, first thing I did was to disconnect everything.
As the G57 weighs in at 24Kg, carriage/convenience is an issue.

Anyway, thanks for the tip and I'll give MRS a ring.
Click to expand...

Don't be a whimp! My 559s weigh 42Kg each (I have two) and boxed 54Kg. No problem by courier and one was delivered by giant haystacks carried in both hands to my garage!

Cheers,

DV
 
I did notice that bridged into 4 ohms, a pair of G57s are rated at 1Kw o/p!

A party at your place must be quite an event. :D
 
I had a similar problem with DC noise and the 248VAC causing hum on the power trafos on my TRON power amp (which was set for 230VAC). I bought a Power Inspired AG1500 mains regenerator - problems both solved.
 
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