[Madskp]

I have just tried to make a test with my BL3500 MK1.

I could not find my adapter cable I have made for it at first so I started by making a minijack to 7 pin DIN cable where I connected pin 3 and 5 in the DIN plug to ground on the minijack, and and pin 1 and 4 in the DIN plug to L and R in the minijack.

Connected to my Macbook pro connected to power I was getting a noticeable hum when nothing was playing. When I removed the power cord from the Macbook the hum disappered.

Later I found the adapter which is a 8 Pin male DIN plug in the speaker end. Pin 3, 5 and 7 is soldered together and is connected to the screen in the cable (original B&O AUX cable used for this) and connected to PIN 2 in a 7 Pin female DIN connector in the other end of the adapter.

Pin 1 and 4 from the 8 Pin male DIN is connected to pin 3 and 5 in the 7 Pin female DIN connector in the other end of the adapter.

Also I have pin 6 (data) connected between the two DIN plugs.

When I use this adapter with a normal minijack to 5 Pin DIN cable I get no hum (that I can hear). Why this makes a difference I can’t tell.

So this hum issue could both be because of power sources and signal cables or a combination of these.

[Ravsted]

Hi,

As you can see in this thread my BeoLab’s are connected to preout of a surround receiver and triggered via a USB power source.

https://archivedforum2.beoworld.ouronlineserver.com/forums/t/45510.aspx

I were facing ‘humming’ in some speakers as well.

Way more in the BL4000 with class AB amps than in the class D IcePower Beolabs (BL7.2 and BL2).

It is the same USB power supply triggering them all.

I managed to reduce the ‘humming’ significantly by using an iPhone charger model A1400 5V 1Amp. I previously wrote iPad charger. That was wrong.

I think you have to accept some ‘humming’ from an old class AB amp. It is normal.

But Apple iPhone A1400 would be my recommendation.

 

 

[KolfMAKER]

Update > Solved

Here’s another update, after having received the Apple A1400 USB wall outlet charger.

I can now confirm it is true. This charger / step-down converter does not cause any Hum. To be exact, there is a little Hum, but only hearable when the ear is within 20cm of the speaker driver.

Important notice: there are many USB chargers that claim to be Apple Original, but are not. Since Apple sometimes changes the design, it makes sense to check the Apple website for information on checking the originality. Mine looks like this and works:

Thanks everyone for thinking with me and suggesting checks and solutions!

 

[Author]

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