[cyclonite]

Hello all,
 
I have spent almost a full day in total trying to resolve an issue. I have been unable to get help from other forums so I've come back here for some assistance.
 
Here's the problem. I have a Phono to RCA Pre-Amp (for turntable). There is a 50Hz buzzing noise on the speaker's output.
 
The pre-amp's body is solid metal. I have attached the 'Ground' cable that runs down the left and right channel of the Phono cable to the grounding screw on the Pre-Amp. This reduces the buzz down to about 40% of its original.
 
Now that the buzz is at 40%, I went on searching for other remedies. I've noticed the the Pre-Amp's metal box is vibrating at 50Hz when I run my fingers over the metal surfaces. This is the same sensation you would get when you do the same on metal Dc powered devices like MacBooks. The problem here is that the AC to DC power supply isn't Earthed. I solved this by running a wire from the Pre-Amp's metal body to the Earth terminal of the wall socket.
 
Now the buzz is down to about 5% but is still audible at loud volumes.
 
I think I need to solve the issue by getting an 'Earthed' AC to DC power supply that outputs 18v at 500mA (although the Pre-Amp's manual says it consumes just 80mA). The problem is, I have been unsuccessful at finding such a product online.
 
I've ordered some ferrite core clip ons to try but I'm not sure whether they'll work.
 
I was looking at 'In-Line noise suppressors' but I'm not sure whether they will work and in any case they don't seem to be made for 18 volts (as most are for car audio systems).
 
The only 2 ways I can eliminate this Buzz is by powering the Pre-Amp by battery (18v) or using a large bench power supply  (digital adjustable type). Obviously those aren't elegant solutions.
 
I don't get why the company doesn't supply an 'earthed' power supply.
 
Is there anything else that I can try?
 
 
Thank you.

 

[Mr Rick]

  Hello all,
 
I have spent almost a full day in total trying to resolve an issue. I have been unable to get help from other forums so I've come back here for some assistance.
 
Here's the problem. I have a Phono to RCA Pre-Amp (for turntable). There is a 50Hz buzzing noise on the speaker's output.
 
The pre-amp's body is solid metal. I have attached the 'Ground' cable that runs down the left and right channel of the Phono cable to the grounding screw on the Pre-Amp. This reduces the buzz down to about 40% of its original.
 
Now that the buzz is at 40%, I went on searching for other remedies. I've noticed the the Pre-Amp's metal box is vibrating at 50Hz when I run my fingers over the metal surfaces. This is the same sensation you would get when you do the same on metal Dc powered devices like MacBooks. The problem here is that the AC to DC power supply isn't Earthed. I solved this by running a wire from the Pre-Amp's metal body to the Earth terminal of the wall socket.
 
Now the buzz is down to about 5% but is still audible at loud volumes.
 
I think I need to solve the issue by getting an 'Earthed' AC to DC power supply that outputs 18v at 500mA (although the Pre-Amp's manual says it consumes just 80mA). The problem is, I have been unsuccessful at finding such a product online.
 
I've ordered some ferrite core clip ons to try but I'm not sure whether they'll work.
 
I was looking at 'In-Line noise suppressors' but I'm not sure whether they will work and in any case they don't seem to be made for 18 volts (as most are for car audio systems).
 
The only 2 ways I can eliminate this Buzz is by powering the Pre-Amp by battery (18v) or using a large bench power supply  (digital adjustable type). Obviously those aren't elegant solutions.
 
I don't get why the company doesn't supply an 'earthed' power supply.
 
Is there anything else that I can try?
 
 
Thank you.

I can't guarantee this will work but you might give it a try.
 
 
http://www.ebay.com/itm/Power-Supply-Board-AC-DC-in-DC-out-Based-on-LM317-IC/250499486450?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3D2feec0115be14cf496b4327f3347f726%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D252173534507

 

[cyclonite]

  I can't guarantee this will work but you might give it a try.
 
 
http://www.ebay.com/itm/Power-Supply-Board-AC-DC-in-DC-out-Based-on-LM317-IC/250499486450?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20131003132420%26meid%3D2feec0115be14cf496b4327f3347f726%26pid%3D100005%26rk%3D3%26rkt%3D6%26sd%3D252173534507

Thank you. I did see some of these.
 
Silly question, what do they do?
 
Thanks.

 

[Mr Rick]

  Thank you. I did see some of these.
 
Silly question, what do they do?
 
Thanks.

 
They will do a better job of filtering and regulating your noisy power supply. I believe your current power supply (  is it a wall wart? ) needs further filtering. 

 

[cyclonite]

   
They will do a better job of filtering and regulating your noisy power supply. I believe your current power supply (  is it a wall wart? ) needs further filtering. 

 
Hi,
 
Thanks. I found some DC to DC (no AC input support) but these are available locally (United Kingdom) and are quite cheap. Would these work just as well or is there an advantage to using the one you have provided?
 
e,g,
 
http://www.ebay.co.uk/itm/DC-to-DC-LM317-Linear-Step-Down-Converter-Regulator-Module-Power-Supply-/252128701896?hash=item3ab40aadc8:g:riAAAOSw9mFWIXf0
 
 
Thanks again

 

[Mr Rick]

   
Hi,
 
Thanks. I found some DC to DC (no AC input support) but these are available locally (United Kingdom) and are quite cheap. Would these work just as well or is there an advantage to using the one you have provided?
 
e,g,
 
http://www.ebay.co.uk/itm/DC-to-DC-LM317-Linear-Step-Down-Converter-Regulator-Module-Power-Supply-/252128701896?hash=item3ab40aadc8:g:riAAAOSw9mFWIXf0
 
 
Thanks again

 
The one I listed has some range of adjustment. Yours does not appear to have any adjustment. If yours are easily available I would give one a try.

 

[cyclonite]

   
The one I listed has some range of adjustment. Yours does not appear to have any adjustment. If yours are easily available I would give one a try.

the one I listed has a potentiometer to adjust the output voltage too.
 
by the way, since these are only 'buck'; would they work with the same input and output voltage? i.e. 18v in and 18v out using the same power adaptor that came with the Pre-Amp?
 
Thanks again.

 

[deadlylover]

  the one I listed has a potentiometer to adjust the output voltage too.
 
by the way, since these are only 'buck'; would they work with the same input and output voltage? i.e. 18v in and 18v out using the same power adaptor that came with the Pre-Amp?
 
Thanks again.

 
That board uses the LM317 which has a minimum drop of around 1.25V of the input. It might still work with your adaptor if the adaptor has an actual output of 19V or so, and the circuit might still function just fine at 17-odd Volts. You should be able to check it with your bench supply.

 

[Mr Rick]

   
The one I listed has some range of adjustment. Yours does not appear to have any adjustment. If yours are easily available I would give one a try.

 
Yes, I see the adjustment pot now.  I think this will have a voltage drop of a few volts. As I said originally. It may or may not work. A higher input voltage would give you the ability to adjust down to 18V, but then, you've basicly built your own small power supply.

 

[cyclonite]

   
Yes, I see the adjustment pot now.  I think this will have a voltage drop of a few volts. As I said originally. It may or may not work. A higher input voltage would give you the ability to adjust down to 18V, but then, you've basicly built your own small power supply.

OK great. Thank you.
 
I can live with that. In the worse case, I'll buy a cheap 20+ volts power supply adaptor to power it.
 
The seller offers a Return policy so there's no risk trying it out anyway.
 
I'll go ahead and will let you know how I get on.
 
Cheers.

 

[Speedskater]

The thread is going in more productive directions, but:
 
I've ordered some ferrite core clip ons to try but I'm not sure whether they'll work.
 
Ferrite chokes are for radio frequency problems,  they start to work at about 1/2 Megahertz.

 

[Budgie]

Sounds to me like you have a ground loop issue.

 

[cyclonite]

  The thread is going in more productive directions, but:
 
I've ordered some ferrite core clip ons to try but I'm not sure whether they'll work.
 
Ferrite chokes are for radio frequency problems,  they start to work at about 1/2 Megahertz.

Ahh ok! I've wasted £5 then

 

[cyclonite]

  Sounds to me like you have a ground loop issue.

Yes it is indeed. I am trying to solve it There are ground loop suppressors but I couldn't find any that are made for 18v

 

[Budgie]

If the phono amp and the preamp both have ground connected power cords that may be the cause. try plogging both power cords in to the same power outlet, if they aren't all ready.