Problem hum / buzz from Power Supply

[kristeva]

Hi all

I recently acquired a home brew Dac from a Hi-fi enthusiast in Italy. It sounds great but the PSU (housed in separate box) has a slight hum / buzz which is amplified through the speakers.

The buzz is apparent when you take the lid off but I can't identify exactly where its coming from. The power lead is 2 pin Schuko - the 13 amp 2 pin adapter I'm using is earthed, (should I convert to standard 3 pin plug?). I'm guessing something in the circuit isn't quite performing as it should.


Any suggestions? I'll try new fuses (when they arrive).

I'm not qualified to go messing around with power supplies. Does anyone know someone in the London / Surrey area, or further afar, who could take a look for me if needed? Any help or suggestions much appreciated. Renumeration provided and a chance to play about with a cool Dac.

An externally hosted image should be here but it was not working when we last tested it.

 

[carlthess40]

Yes you should be using a 3 pin cable
If you look at the inside on your pic you see he hooked up the earth ground to the red B- strip that has the other wires hooked to it
Using a earth ground may or may not help
Easy thing to try first before digging into it

 

[Mark Whitney]

It is the green/yellow wire that is connected to the chassis.

 

[jan.didden]

The buzz is apparent when you take the lid off but I can't identify exactly where its coming from.

That would mean it is mechanical. But then how does it get to the speaker?
Is it mechanical or electrical?

The remedy for each is quite different.

Jan

 

[kristeva]

Yes you should be using a 3 pin cable
If you look at the inside on your pic you see he hooked up the earth ground to the red B- strip that has the other wires hooked to it
Using a earth ground may or may not help
Easy thing to try first before digging into it

Thanks Carlthess,

Yes you should be using a 3 pin cable

so yes to wiring a 3 pin plug? Am I correct in assuming the light blue is 'live' and the black 'neutral'? I'm not familiar with EU colour coding.

If you look at the inside on your pic you see he hooked up the earth ground to the red B- strip that has the other wires hooked to it
Using a earth ground may or may not help

Should I remove the earth wire from the B - Strip completely and solder it individually to a lone point on the chassis?

Cheers. P

 

[kristeva]

That would mean it is mechanical. But then how does it get to the speaker?
Is it mechanical or electrical?

The remedy for each is quite different.

Jan

To be honest I wouldn't know the difference Jan if its getting to the speakers I assume it must be electrical then?

 

[Keruskerfuerst]

Can you post the schematic of the power supply ?

 

[carlthess40]

Yes you should be using a 3 pin cable
If you look at the inside on your pic you see he hooked up the earth ground to the red B- strip that has the other wires hooked to it
Using a earth ground may or may not help
Easy thing to try first before digging into it

Yes the green/yellow wire is earth ground

 

[CallMeMike]

Hi all

I recently acquired a home brew Dac from a Hi-fi enthusiast in Italy. It sounds great but the PSU (housed in separate box) has a slight hum / buzz which is amplified through the speakers.

The buzz is apparent when you take the lid off but I can't identify exactly where its coming from. The power lead is 2 pin Schuko - the 13 amp 2 pin adapter I'm using is earthed, (should I convert to standard 3 pin plug?). I'm guessing something in the circuit isn't quite performing as it should.


Any suggestions? I'll try new fuses (when they arrive).

I'm not qualified to go messing around with power supplies. Does anyone know someone in the London / Surrey area, or further afar, who could take a look for me if needed? Any help or suggestions much appreciated. Renumeration provided and a chance to play about with a cool Dac.

(end of quote) ..................................................................................... Replacing the fuses will achieve nothing for reducing or removing the buzzing sound... The wiring seems to be fine from an electrical point of view. If you have access to a multimeter you could check the continuity of the ground/earth wires but only if you know what you are doing and WITH THE MAINS CABLE UNPLUGGED. Probably it's best you check for a South London/Surrey qualified person to carry out the appropiate investigation (Internet search, nearest High Street, etc).

 

[Alan4411]

... so yes to wiring a 3 pin plug? Am I correct in assuming the light blue is 'live' and the black 'neutral'? I'm not familiar with EU colour coding.

Make it Safe first.
Fit a UK mains plug with a 3 Amp fuse.
Green / Yellow to the E Earth pin.
Blue to the N Neutral pin. The convention is Blue is Neutral in the EU.
Black to the L Live pin.

That might or might not stop the buzz in the speakers, but at least will be safe.
The buzz from the case will most likely be one of the transformers. (The 3 objects under the silver discs in your picture.)
But fit the 3 pin plug so the unit is earthed before anything else please.
Alan

 

[kristeva]

Thanks all for the responses.

I changed the earth wire last night to a lone position on the chassis but to no avail unfortunately.

I've managed to find a few people local to me who can help from various sources.

 

[Rick PA Stadel]

From what's been described so far, I thought the grn/yel wire just dead-ended somewhere (at the other end of the wire) -- didn't your original post mention just 2 pins on the plug? Gotta get that puppy solid-earthed before you do anything else with the cover off. An unearthed piece of equipment is potential trouble enough with the cover on.

Good, safe luck,
Rick