Shielding cage for transformer

[heady 0]

I am finishing up on my PPA and there is a soft buzz now even with my DT880 just at the volume level, just past mid-level, that I listen at most.

 

Interestingly, this buzz was not discernable on my DT earlier but were clearly heard on my low impedance phones. Now I have tidied up the wires by shortening the power cables and twisting them etc, the buzz is now louder.

 

I understand the buzz can be minimised by using a shield built of a magnetic material, like steel. Where can one find such a material to do this? Or can one buy a ready made cage which is not expensive. Remember, I am stingy...

 

Thanks guys.

 

[jasonhanjk 0]

You can try to move the transformer furhter away from the amp.

[heady 0]

Thanks Jason, I can't move the transformer any further. I found the reason for the louder buzz and it is outside the amp. I was careless and placed the AC supply cable beside the signal cable from the CDP.

 

Once I moved the AC cable, the buzz decrease to barely discernable. But I would still like to decrease the buzz inherent to the amp if it is possible. So will try to find a source of sheet metal.

 

[jasonhanjk 0]

Best shield that I know of is Silicon steel, it may sounds funny but someone told me this. Don't know it's availability though.

[heady 0]

I will settle for just plain mild steel which is thin enough to cut and fold. Use to see an old man who came around with a portable blowtorch and pieces of steel, and he does all sorts of soldering and repair. From pots to the iron roof sheets. Of course you all young people cannot imagine this.

[zonalblitz_audio 0]

heady, if you were to bring this up much earlier, i might be able to bring some sheets of aluminium or mild steel for you. There are plenty of leftovers after every welding lessons.

 

By the way, what is the dimension you require for your work? And is the transformer covered or with exposed core? In fact, i think you may not necessary go for Steel sheets. Any material with 'dense-molecular' properties will do the same since it's not high powered or sensitive.

[heady 0]

Hi, what course are you taking? Sounds cool, to do welding and fabrication. Wish has these courses when I was young. Thanks for thinking about it. Not to worry, my brain is ticking to see what can be tried as cages.

[siriuz 0]

This wikipedia article might be helpful ..

 

http://en.wikipedia.org/wiki/Electromagnetic_shielding

[huangyong 0]

Hi heady.. i faced the same problem before, just tell you that it is definitely not mainly caused by transfomer.

[zonalblitz_audio 0]

I'm in Marine Engineering. We are taught to be experienced with welding(Hot weld, arc weld, MIG welding, tungsten welding etc), not trained to be professional welders.

[heady 0]

Hi heady.. i faced the same problem before, just tell you that it is definitely not mainly caused by transfomer.

 

Thanks, I know as I found if the mains power cable is close to the interconnect, the buzz is louder. In your experience, what else can cause this buzz?

 

[loop_ 0]

you can try maybe moving the transformer outside of the casing for awhile, as far as possible, and see if there is still any noise. if there is then shouldn't be the transformer?

 

[heady 0]

Thanks loop , I also thought of doing this experiment last night (great minds think alike? ) but had no time to try it yet.

[huangyong 0]

haha..loop is learning fast..

 

anyway.. ur buzz might be due to grounding prob.(pot to amp to rca)

if your amp only picks up noise when the pot is turned to certain degree, then it is most likely grounding problem.

[heady 0]

I had the pot connected to the pcb ground and it had the buzz and so I removed the connection but the buzz is still there. The pot is not isolated and so is connected to the mains earth. And I was wondering if the connection of the pcb ground to the mains earth is a problem or not. Anyway, I am puzzled by all this and will find time to slowyly try different things to see if there is any difference.

 

Thanks.