Thanks Srdjan!
Which jumper do you refer to?
Weâve added a jumper on latest mini v3 board, and only one jumper to cut the ground. And if not found, it might be old batch.
May be a version issue. I will put money on it youâve got your signal ground connected to the wrong place so hang fire on cutting links on the Mini V3, changing psu etc.
Can you probe the ground pin in the DIN connector and see where that leads? It may be via a different route than the P4.
To test we are on the right track temporarily connect the Mini V3 into the DIN. You could make up a 3.5mm Jack to DIN test lead to do this although the auto start may not be fully functional.
Simon.
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General update.
Last weekend I tested with a headphone directly connected to the mini-jack on the Up2Stream Mini. This proved that the outgoing signal of the Up2Stream is clean: no noise/hiss.
Just to be sure I now used this mini-jack audio out of the Up2Stream Mini, to connect it to the amplifier Audio-In of my active speaker. Result: the noise/hiss is still there.
Now we are scratching our heads 
@KolfMAKER Maybe you have already tested these but what happens with different sources on Mini V3 e.g. Internet Radio, Another streaming Service ?
Also what happens when you use a completely different Source/Preamplifier ?
Regards Kevin.
Thanks Simon!
I am not sure I understand what you mean with âhang fire on cutting links on the Mini V3, changing psu etcâ
Can you please clarify?
I didnât test yet with mini-jack to DIN. But I was able to with mini-jack to cinch. In this case: noise/hiss is gone. Though there is some hum.
I just meant donât make any other changes until youâve connected via the correct signal ground. Too many variables would mean I wouldnât be able to fathom what was going on.
Anyway, so now you have the Mini V3 connected into the B&O speaker using the the correct ground the noise has gone, but instead there is now a hum?
Are you connected via the DIN or RCA (phono) connector instead of the P4?
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Thnx Simon, I get it with changing variables. My method is always change only one at a time.
Anyway, so now you have the Mini V3 connected into the B&O speaker using the the correct ground the noise has gone, but instead there is now a hum?
Answer: Yes, correct. Noise/hiss is gone but thereâs a hum.
Are you connected via the DIN or RCA (phono) connector instead of the P4?
Answer: This test was based on connecting the Up2Stream Mini via mini-jack to the RCA input of the BeoLab.
Tonight I will test by connecting the Up2Stream Mini to the BeoLab P4 connector, but only on pin P4-1 and P4-2, and for ground connect with ground from the DIN.
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Another test: I now also tested by connecting the Up2Stream Mini via mini-jack, directly to the DIN-input on the BeoLab.
Result: noise/hiss is gone ( 
). Though there is some hum (
).
So it is interesting that if I connect directly to the physical inputs for RCA or DIN (using the L/R wires and GND of those connectors), instead of connecting to connector P4 on the Amp PCB, the noise/hiss is gone.
So the main problem has been tackled. But it creates a new situation: hum, sometimes consistent, sometimes sounding like a rattle.
I tried to make several ground connections to see if it would disappear, but so far no success.
Now seems youâve got grounding loop or psu induced noise so sticking with the audio plugged into the rca or din, try a different psu, say a usb type as proposed earlier and see if that eradicates it.
I used one of those cheap smps youâre using on a vhf radio I was refurbishing and it was far too noisy so I had to swap it out.
I just tested following:
- Up2Stream Mini via mini-jack audio-OUT connected to RCA audio-IN at the BeoLab amp.
- Up2Stream Mini powered via USB with a battery pack.
Result: Is same = noise/hiss is gone, but hum is still there.
So the battery pack seems not to influence.
It does not eliminate the hum.
Besides hum, there is also a kind of ârattleâ hearable.
If you have any ideas for next steps, I would appreciate!
Hi,
So in summary you are powering the Mini V3 by battery (connector 8) which has no electrical connection to mains or the speaker, and have an audio lead that connects the Mini V3 3.5mm socket (10) to the B&O Phono?
Can you confirm the connected pins are as follows: 3.5mm plug pin 1L (or pin 2R) to RCA pin 1, and 3.5mm pin 3 GND to RCA pin 2 GND?
If the above is true, have you tried plugging a CD Player or something similar into the B&O to see if the same problem exists? As youâve tried headphones direct in the Mini V3 and powering it by battery I suspect the problem is associated at the B&O speaker end. I notice there is no decoupling capacitor in the B&O so so inserting a 2uF cap could be something to try next. The value wonât matter for the purposes of this test.
Simon.
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Thnx Simon, for your perseverance in helping me!
Powering the Mini, I have tested two situations:
a) Via an AC/DC power supply that gets its power from the 230v AC pins inside the BeoLab (where they lead to the B&O transformer, so more or less tapped). The 5v DC output goes to connector 8 of the Mini.
b) A 5v battery pack, connecting via USB to connector 7 of the Mini.
In both (a & b) there is a hum, with the battery pack it seems slightly less hearable.
Audio connection:
This is indeed a mini-jack (stereo) from the Up2Stream side, going to a RCA plug (mono) to the BeoLab side. The wires and connected pins are as you describe. Though, on the RCA side, there is only Left or Right connected to pin 1 (not both).
Alternative source connected to RCA:
Yes, I have tried a different source; an iPhone. Also in this case there is a hum.
Decoupling capacitor
Your observation sounds interesting. If you still advise this after reading the above, can you please mention where the capacitor should be connected?
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If you get the hum with the iPhone too then it is the B&O thatâs the problem.
You could try inserting a cap into the signal line to decouple, but to be honest weâre are clutching at straws now and there is probably something else wrong with the B&O that I canât help diagnose from here.
Simon.
2 Likes
Thanks Simon! Hopefully weâre getting close now.
Inserting the cap, would that be like in this scheme?
To be sure:
-
If I use the RCA input, I only have a GND and L or R, so 2 wires. Should the capacitor be connected with minus to GND and plus to L or R?
-
If I use the DIN input, I have a GND + L + R. Should the capacitor be between L and GND + between R and GND? (So 2 capacitors)
-
Does the exact spot of inserting the cap matter? Should it be as close as possible to the Audio input at the amplifier side?
-
Is the type of capacitor like this? I think you mentioned the voltage doesnât matter? 2.2 uF 50V condensator - Ben's electronics
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You need to put the decoupling caps in series with the audio signal. Break the L red and R and insert as below. Put the +ve for both at the Beolab end, although donât worry too much. Value of 2.2uF / 6.3V will be fine. Higher voltage spec wonât make a difference and are just slightly more expensive.
All we are doing here is using the cap to ensure DC voltage present either at the Mini V3 or the BeoLab are isolated.
The other thing to try, as youâre ordering some caps, is buy a couple of 10k resistors and put them between L+G and R+G on the BeoLab side.
I noticed earlier @Joanb14 suggested an isolation circuit that you said youâve ordered. If you already received it try that as that goes the full hog as it includes an isolation transformer.
However, I actually think there is something else wrong with the Beolab as you have hum with other sources but the above is an easy test.
If you have a multimeter can you check the Beolab ±15 supply voltages (IC2 pin 4 and pin 8) wrt ground?
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@SimonB This is very useful information generally. Thanks for posting. Kevin
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Very professional and detailed suggestions, just great! And can I suggest to replace the amp board inside the B&O speaker with Up2Stream AMP? 
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Ah sacrilege!!! 
It could be done but the Beolab speaker has an active crossover so @KolfMAKER would then need to design a passive for the tweeter. Iâm out 