The MCL connector on the BL3500 MKI will accept both speaker level inputs as stated in B&O specifications, and line level inputs as shown in the use case for the MCL connector in post 3 in this thread. I have also made some tests with this connection in this post https://beoworld.org/forums/topic/beolab-3500-and-1611-converter-settings/page/17/#post-17044
and found out that signal and ground can be reversed.
Looking at the diagram in the Beomaster 5500 servicemanual I discovered that the dataline for the MCL speaker connectors are connected to pin 6 in the AUX din, so I started wondering, could this also be used for connection between the Beomaster 5500 and the Beolab 3500.
As the pinout for those connections are different I made a custom cable:
BM5500 pin 2 – > BL3500 pin 3 and 5
BM5500 pin 1 – > BL3500 pin 1
BM5500 pin 4 – > BL3500 pin 4
BM5500 pin 6 – > BL3500 pin 6
Pin 7 on the BM5500 is datalink for tape and CD, so that is not used for this.
Tested with the setting ML off in the BL3500 service menu (Menu+0+9+GO)
This was not working.
Wondering and going through diagrams and pinouts for the different connectors I noticed that the BL3500 has data shield on pin 7 connected directly to ground internally.
But where should I connect that in my custom cable? Looking at MCL pinout’s answers that question:
Ground on both speaker connectors as well as data shield is all connected which means that pin 3, 5 and 7 in the BL3500 MCL connector all has to be connected:
BM5500 pin 2 – > BL3500 pin 3, 5 and 7
BM5500 pin 1 – > BL3500 pin 1
BM5500 pin 4 – > BL3500 pin 4
BM5500 pin 6 – > BL3500 pin 6
Tested with the setting ML off in the BL3500 service menu (Menu+0+9+GO)
Success
This is working just the same as with the MCL connection 🙂
Voltage readings on the data pin (pin 6) are the same 4,68V as I registered with the MCL connection
One thing to note from this test is that the BM5500 is the only product where I have found that the data pins in the Aux connector and the MCL speaker connector are connected internally in the Beomaster, so the result of this test might not be the same with other audiomasters.
One other note that I don’t know if has any relation to this is the description of an obsolete Powerlink cable in the Beolink handbook where it is stated that pin 3 and 7 are short circuited. In my head that doesn’t make much sense in a powerlink cable where pin 3 is signal and 7 is data ground, but might make sense if it was used somehow with the BL3500??