Step-down (220->120) transformer noise: which route to take?

[xaphod]

Hi there,

I've just moved to Switzerland from Seattle area. I brought with me my set of cheapo-but-okay hometheater 5.1 speakers, the Logitech Z680 (bought in Canada, 120V version). I've plugged it into a 500W step-down transformer (from swiss mains which i believe are 220V 50hz). It works but there's significant "noise" - i've read that hum is different than buzz. Let me start by saying it is not a ground loop because the Logitech Z680 has no ground pin on its AC plug It is not coming out of the speaker, it is comign out of the "transformer" in the z680, i'm pretty sure about this.

I've read about products like the Belkin PF60, and PS audio products like the "humbuster AC". Problem is, they are a little expensive. I'm hoping that since this hum doesn't exist when i hook up a different lower-wattage technics stereo to the same transformer, this means that it is something simple.

Could it be that since the Z680s are rated at 505W RMS and my step-down transformer is only 500W that i'm pushign the step-down transformer too hard, and it is distorting the power as a result? What i'm asking is which route should i take: buy a bigger more powerful transformer, or invest in power-conditioning equipment? The key here is to be economical DIY is almost impossible in switzerland, they just don't do DIY here

thx!

[ThomasW]

I suspect it's something in the design of the Logitech power supply that doesn't like being plugged into the step-down transformer..

[xaphod]

uh oh. I sure don't like the sound of that. What can I do to test this theory, or to try and get rid of the sound? Woudl a larger transofrmer (1000w instead of 500w) possibly make it better? Toroidal better than E-I?

all help appreciated ;x( . I really can't afford to buy another 5.1 system

right now i'm looking at buying this one in december.

[audioqueso]

No offense, but for the same price to buy a transformer, wouldn't it be easier just to buy the Europe version of the Logitech Z680?

[sirbogey]

. DIY is almost impossible in switzerland, they just don't do DIY here

That's quite a statement! :rofl:

I'm from the infamous cheeseland myself and trust me DIY is big over there. You being new to Switzerland just don't know where to look. What exactly are you trying to buy? And what area are you in? Maybe I can put you in the right direction....

[Scooter]

50 vs 60 Hz

Well, it has most probably nothing to do with beeing plugged into a stepdown transformer. The US do use a 60 Hz frequency and Europe uses 50 Hz. And most transformers don't like the "other" frequency at all. Most of them (even in expensive gear) start to rattle around. Unfortunately there is no cheap way out of this, so in your case it is probably the best to get some European gear (in the sense of Made _for_ Europe, not necessarily in Europe).

As for the DIY scene: From most parts of Switzerland it isn't that far to Germany...

[xaphod]

Wahoo! After much smashing about, I managed to solve the problem: I opened it right up and determined that it was indeed the transformer inside the sub that was making the noise. (It was a toroid). I put foam underneath it to stop it vibrating agains tthe wood of the sub and that fixed the problem! (well you can still hear it a tiny bit but it's MUCH better)

WOOHOO!

btw, I posted pics:
here you can see the inside of the z680 with the sub speaker removed. The toroid power transformer is at the bottom right of the photo. No, you cannot get through from the back!

http://www.fuzzymunchkin.com/tdot/g...2_itemId=132367

here is a schematic copied from the front of the power transformer (toroid) in case you want to change it or something... (i was thinking of putting a new one in that did 230v mains but now i don't need to since hum is gone)

http://www.fuzzymunchkin.com/tdot/g...2_itemId=132364

I'm a happy guy now. 300 is playing...

[xaphod]

That's quite a statement! :rofl:

I'm from the infamous cheeseland myself and trust me DIY is big over there. You being new to Switzerland just don't know where to look. What exactly are you trying to buy? And what area are you in? Maybe I can put you in the right direction....

Sorry, no offense meant, I was only repeating what has been told to me a bunch of times... But I don't know tons of people here so I can hardly say they speak for all of switzerland ops:

But hey, problem solved (see above) - i'm a hppy guy.

[sirbogey]

interesting solution and no offence taken. btw: your links don't work.