[BrunoB]

I just bought a new amp for my subwoofer: a Hypex DS8.0:



There is one problem with this amp: there is a background noise that disturbs me because my driver is quite sensitive and because the sub is placed very very close to the listening position (see http://www.audiocircle.com/index.php?topic=54844.0)


The huge transformer emits a typical "transformer noise". The problem is that I can hear the same noise coming out of the speakers.

I have sent the amp to the Hypex repair service in Holland. It came back after 10 days - I have the impression that the noise level is lower but I am not sure.

I tried two things to fix this problem:

• make a shield of aluminium foil around the transformer - no improvement
  
• connect the two drivers of my sub in series - the noise is much less audible

Here is a picture of the transformer:


I have placed more pictures in my album http://www.audiocircle.com/index.php?action=gallery;area=browse;album=1873.



Thanks in advance for any suggestions,

Bruno

[BrunoB]

Looks like a solution to  my problem has been described : http://www.audiocircle.com/index.php?topic=12706.0

I plan to buy a DC filter.

Bruno

[JoshK]

Another idea to try (not saying it will help, but it could):
Try to isolate the transformer from the case somewhat, by placing a dampening spacer of some sort between.  a couple of large rubber washers might work, or dynamat could help.  The idea is if the transformer is vibrating (touch it if you can to see) this can couple to the amp through the chassis it is bolted to. 

You can try the DC filter idea.

For kicks also try moving the two black leaded wires further away from the yellow wires.  If they are easiely disconnected, try twisting them a bit.

[BrunoB]

Another idea to try (not saying it will help, but it could):
Try to isolate the transformer from the case somewhat, by placing a dampening spacer of some sort between.  a couple of large rubber washers might work, or dynamat could help.  The idea is if the transformer is vibrating (touch it if you can to see) this can couple to the amp through the chassis it is bolted to. 

You can try the DC filter idea.

For kicks also try moving the two black leaded wires further away from the yellow wires.  If they are easiely disconnected, try twisting them a bit.

I once remove the tranformation from the plate and holding it in my hand. Then I turned the amp on and I could still hear the noise from the speaker.

I ' ll try to move the yellow wires away from the black ones.

I plan to buy a tk-audio DC filter (for safety reasons, I don't want to build one my self). It will take a month to get one.


Thanks for the suggestions,

Bruno

[BrunoB]

You can try the DC filter idea.

For kicks also try moving the two black leaded wires further away from the yellow wires.  If they are easily disconnected, try twisting them a bit.

Moving the black wires: no effect
DC filter: no effect  . I used the TK/Audio DC filter http://www.tk-audio.de/testberichte.html
.

[JoshK]

Bummer.  Did you try contacting Hypex?  They are pretty responsive on some of the forums.  They might have some ideas.  I've exhausted my ideas. 

Do you have a scope?  You could try probing to see where the hum starts.

Is it 60hz hum?  Could it just be a ground loop?  Try eliminating as many possibilities as practical.

[BrunoB]

Bummer.  Did you try contacting Hypex?  They are pretty responsive on some of the forums.  They might have some ideas.  I've exhausted my ideas. 

Do you have a scope?  You could try probing to see where the hum starts.

Is it 60hz hum?  Could it just be a ground loop?  Try eliminating as many possibilities as practical.

Here is a spectrum of the background noise:


The yellow line shows the background noise of my room. This is not a ground loop - the noise is present even if the amp is connected only to AC.

Bummer.  Did you try contacting Hypex?  They are pretty responsive on some of the forums.  They might have some ideas.

Which forums do you have in mind? I might post there as well.

Thanks,

Bruno