Beolab 7.4 hiss with BeoPort and Beolink Active

[Blokkenpiloot]

Hi all,

I used an Beosystem3 for driving a Beolab 7.4 speaker, which worked great!

But when i connected it to an Beolink Active, there was an high pitched hiss, and an rumble.
Even without volume or without connecting an audio source.

it’s not the hiss you get from loud volume, because when i increase the volume, the constant hiss stays the same until an point about 2/3 high, and then increases with the volume. It has the same sound though, but will remain even at lower volumes.

I made an custom cable connecting pin 2 and 7, and on the Beoport, there isn’t any rumble anymore with the 7.4 speaker. Great!

But the 7.4 still has the higher pitched hiss compared to the Beosystem 3, with all cables the same!

I couldn’t get this trick to work on the beolink active though.

How can i better tackle this issue? is there another device that i can use instead of the beolink active or beoport? Ofcourse i can use the Beosystem 3, but that’s a bit overkill for only one 7.4 speaker.

Thanks!

[Madskp]

Hello

At least in some products pin 2 and 7 are internally connected in the device or pin 7 is not connected at all.

An idea could be to disconnect pin 7 in the cable to see if the hiss disappear. My suspension is a ground loop.

[Blokkenpiloot]

Hi There, Thanks for your suggestion.

I just desoldered pin 7, which i connected to pin 2. And the deeper hum was back.
When i touched the (loose) wire 7, to pin 2, the hum was gone again, and only the high pitched “static” was back.

On the BeoPort/PC2, the static volume is about 60, because when i increase the pc2 volume to over 60, the static noise will get louder, but under 60, stays at the same volume.

I also noticed when my ear is almost inside the tweeter, there is an small “Ticking” sound every second.

4 audio files are added, all recorded from the same distance and without audio inputs on the PC2, i even removed the USB connection but no difference. So only power and the powerlink are connected.

The hum on the beosystem 3 is the same sound, but way lower in volume, and without the tick every second.

(can’t add audio files, so hosted them myself, right click and save as, to prevent addblocker)
https://www.aymeric.nl/hum_with_2_and_7_volume_0.m4a
https://www.aymeric.nl/hum_with_2_and_7_volume_72.m4a
https://www.aymeric.nl/hum_without_2_and_7_connected.m4a
https://www.aymeric.nl/hum_same_cable_beosystem_3.m4a

[Madskp]

Blokkenpiloot wrote:

I just desoldered pin 7, which i connected to pin 2. And the deeper hum was back. When i touched the (loose) wire 7, to pin 2, the hum was gone again, and only the high pitched “static” was back.

I am a little unsure what you actually did when you write that you desoldered pin 7 and connected it to pin 2, but you also have a loose wire?

Just to clarify my idea was to remove the connection to pin 7 in both ends of the cable and not use that wire at all as the wire on pin 2 also is a ground connection.

Not sure if it will work as the official B&O powerlink cables does have both ground connections.

Also maybe check your pinout with those in the Beolink Handbook from page 102 https://beoworld.org/beolink-handbook-version-1-9/

Note that there are several versions.

[Blokkenpiloot]

Thanks, i’ll look into that handbook.

To clarify:
1. I took the powerlink connector on one side of the cable. And desoldered the wire to pin 7, which then hangs loose. So pin 7 didn’t make any contact with the Beolink PC2.

2. there was an deep rumble coming from the speaker

3. i then soldered a small wire to pin 2, next/on to the original ground attached to pin 2.

4. i then touched the other end of that wire to the wire i just soldered off of pin 7. So on the Beolink PC2 side, pin 7 was still disconnected, and on the speaker side, pin 2 and 7 were connected.

5. The deep rumble was gone, but the high volume hiss stays. It’s the same as keeping all 8 pins connected on the cable, and connecting a small wire between pin 2  and 7.

6. When using the same self soldered wire on the Beosystem3, the high hiss is present, but at a way lower volume compared to the Beolink PC2, both with volume on 1 (on zero will be quieter) AND on the Beosystem3 there is no ticking noise once a second, but that’s not audible from a normal distance, this hiss is.

[Blokkenpiloot]

At the handbook they refere to pin 7 with the “braided shield”, on my cable it’s the other way around. Pin 2 has the shield and 7 the other ground.

I can try to change it around, but since it’s working with this cable on my Beosytem 3, i don’t think it’ll work. But it’s easy to try!

[Madskp]

Blokkenpiloot wrote:

At the handbook they refere to pin 7 with the “braided shield”, on my cable it’s the other way around. Pin 2 has the shield and 7 the other ground. I can try to change it around, but since it’s working with this cable on my Beosytem 3, i don’t think it’ll work. But it’s easy to try!

that might have something to say.

With original powerlink cables this behaviour can also differ from product to product depending on the type of powerlink cable used

[filip_kbh]

In the manual for the 7-4 it says to use a specific type of Powerlink cable as others can cause hum.

[Blokkenpiloot]

Yes i know, MK3. But it’ll hum with all cables, (Old full wired powerlink, MK2 and MK3) on the Beolink PC2, and with the same cables on the BeoSystem3, its good.

[RaMaBo]

Hi,

 

the Beolink active (1636) has a different connetion option than the older Beolink active (1616).

The older has two powerlink connections which should work flawlessly with a MK3 powerlink cable.
The newer Beolink active (1636) has one connection as PC (to the computer) and _one_ powerlink connector.

 

May be the BeoLab 7.4 is connected to the wrong socket? It should be connected to the powerlink socket.

 

[Blokkenpiloot]

I have the active with PC and Powerlink. It’s attached good, because there is sound (playing from the PC port into the Powerlink socket, but even without the PC port connected, the “hiss” stays)! So yes it works, but there is an way louder “hiss” sound coming from the 7-4 when connected to the Active, Beoport, compared to the BeoSystem 3

But yes maybe i’ll try that older one if i come across one, didn’t know about the difference, thanks!

[Author]

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