Transformer hum

[Silent]

I've had my BPS1500 mains supply from Airlink for about a year now and I've know about the mechanical humming since I first installed it however it was hidden in a cabinet so the noise was not intrusive. Circumstances have caused the BPS to be out in the open and the humming is very loud.

Does anyone with experience with this product know of any solutions?

Context: The BPS is powered from a wall socket with 2 sockets (one empty). It is powering a Quad Vena II with one of its outputs and an extension bar (attached to which is 2 monoblocks and a Innuos Zen Mini MK3) with the other output. There is a TV and a blu ray player near the BPS but not powered by it.

Cheers,
Nick.

Sent from my SM-G988B using Tapatalk

[Barry]

What is the mains voltage where you reside? If it is higher than 230V + 10% (i.e. 253V), then there may be problems.

[Pigmy Pony]

You did say it was a mechanical humming - could the casework not be removed and the source of the hum (vibration?) located? Then maybe damped? I'm just speculating as I've no idea what a BPS1500 mains supply is :doh:

[walpurgis]

If the mains transformer is a bolted together frame type, it could be the bolts want tightening to stop the plates buzzing. Or the transformer needs isolating better or tightening down.

[Macca]

I'd just get rid of it and plug the amp directly into one of the wall sockets and the other equipment into the extension block.

[Pigmy Pony]

I'd just get rid of it and plug the amp directly into one of the wall sockets and the other equipment into the extension block.

That's what I do, my amp gets it's own socket, everything else has to share the other one.

[sailor]

You could have some DC riding on the mains. Dimmers and suchlike can cause this. Perhaps switch all breakers off and see if the hum remains. If the hum has stopped then turn breakers back on, one by one, until you find the offending circuit.

[zanash]

agree ..try the audiolabs dc blocker

[Barry]

When no secondary current is being drawn the transformer's core is at maximum flux density, and a DC offset causes partial saturation during one half of the AC cycle. The transformer's magnetising current waveform becomes asymmetrical, and when the core saturates in this way it leads to magnetostriction, a condition where the physical size of the core changes. It's only a very small change, but it often causes the core to mechanically vibrate or 'buzz' at 100Hz. This can be very audible, and (somewhat predictably) it's not something that anyone likes to hear. Big transformers (500VA and above) are the worst affected because their winding resistance is so low.

Since your toroidal transformer has a rating of 1500VA, even a small amount of DC on the mains can cause problems. The only real solution is to fit a well designed DC blocker in the primary path.

[swampy]

If it is mechanical hum and not mains DC then the only solution is TX isolation. I have experienced exactly the same thing in DIY builds and it all came down to the quality of the transformer used. The cheaper torriodal ones are the worst offenders, far worse then conventional rectangle type TX.

As suggested try tightening the bolts but this is not usually the solution unless it was very poorly bolted in the first place. As a simple test try loosing the bolts quite some; to see if the noise reduces. The TX transfers its vibrations to the chassis so loosing them temporary as a test should prove it. In which case you then need some rubber isolation under the TX. I have used cheap pound land foam pads in the past and a block of soft wood 1-2 cm thick bolted between the TX and chassis made a vast improvement. Sometimes the thin rubber pad under the torroidal TX is not enough to isolate mechanically.

Rule out the DC issue first.