ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hello!
As you know, the Beomaster 5500 has no proper preamp outputs, because these are taken from the amplifier output and are attenuated. A bit silly, or was there a good reason for this?
Wouldn't it be better to mod these outputs by taking the signal directly from the amp inputs?
Has anybody tried this mod? It wouldn't be too difficult, just cutting two tracks and wiring the sockets to the point between the 1k resistor and the 2.2 μF amp input cap (R202/C201). I don't really like the idea of taking the signal just after the tone control op amp though.
Would this output be able to drive the long cable runs without attenuating treble?
Cheers!
Jacques
I've done this Jacques,by simply adapting the preamp to the same configuration as the Beomaster 6500.The preamp and output stage are essentially the same in the two Beomasters,but of course the '6500 has powerlink outputs.
The mod works well.You can connect the extra components directly to the pcb,then run a single cable form out (powerlink cable) to a trailing 8 pin din socket.
When B&O active speakers are connected,the auto power up and muting are maintained,and of course the output stage is released to supply more power to link rooms.
Regards,
Nick
Thanks Nick. Mod done. It works but there is not that much difference in sound quality, perhaps the treble is more finely etched and bass less prominent. Amazing!
Please note that my Beomaster 5500 doesn't have the famous extra caps.
Here's what I did, very straightforward. I just removed the bottom cover (you do have to slide the top cover slightly forward) and soldered the two 1k resistors at R253/453 (copper side) with two solid core wires going directly to the output sockets. I cut the two tracks near them. In my haste to see how well this worked, I forgot the pictures...
Yes indeed,that's it. I made mine up to provide powerlink output including the "play" voltage,and mute for penta's.I think there are some decoupling caps too?I'll sort out my notes.
I think the extra caps issue is something of an "urban myth"? I was intrigued,so looked into it,but they seemed to be part of a an rf filter network to limit the high end response of the phono pre-amp?
Feasable that it could affect the sound of the phono stage I 'spose,but I doubt it could be heard?
What speakers are you using with the modded pre-amp output?
Yes there are 1nF decoupling caps, but I see little point in fitting them. Am I wrong?
I use Beolab 6000 speakers.
Please check your notes Nick!
Could you provide some information on how you wired the Power up/down and Mute circuit.
Thanks
Martin
Yes indeed.If you use a section of powerlink cable,you can connect the grey wire via a 1k resistor to the collector of TR5.The other end then will connect to pin 1 of of a trailing powerlink (8 pin) socket (MUTE)
Connect the yellow wire via a 470 ohm resistor to the collector of TR2 ,the other end to pin 4 of the socket (POWER UP)
Connect audio out to pins 3/5 of the socket.Jacques(above) has used the original pre-amp output sockets,which is ok if you are using auto power up,but does'nt allow muting.
The display data for Penta's,Beolab 3000/4500/5000,can be picked up at TR3 collector.Use the tiny screened cable integral to the "fully wired" powerlink cable,with the centre core going to TR3 and the screen to ground.The centre core then goes to pin 6 of the socket,and screen to pin 7
Hope this helps?
Excellent! Let's hope that all Powerlink cables have the same colours!
Thanks Nick. I've been wanting to make a "Powerlink" connection on my BM5500 for some time. The info you have provided is just what I was after.
Hi Martin,
Don't forget to take photos of your work in progress!