Hiss and quiet music with Transmitter 1 and Beolab 18

I have a Transmitter 1 plugged in by RCA to the variable output of an Audiolab M-Dac + and paired wirelessly with Beolab 18s. The sound from the Beolab 18s has a loud hiss and I can hear distorted music with the hiss. If I turn up the volume on the preamp of the Audiolab very high and unplug the Transmitter 1 then the Beolab 18s work perfectly with no hiss and then I have to turn the volume down to a comfortable level. Obviously not acceptable. I assume the issue is the settings on the Transmitter 1. Can anyone recommend what line in settings I should try to alter on the Transmitter 1 using a USB stick? The system is currently somewhat unusable!

Hi jamesjackson,

This does sound strange. It could be helpful to identify if the issues are being caused by the Transmitter or the M-DAC.  Can you try connecting the speakers directly to the pre-out socket of the M-DAC with a cable please and set them to "L" and "R" via the switch on each speaker?

If this cures the issues then they are likely to be caused by the Transmitter 1.

Kind regards, Steve.

Hi jamesjackson,

1. Make sure that the Transmitter 1 has the latest software ( a few updates since introduced ),

this has to be checked by B&O engineer.

2. Try connecting another source to it.

3. If still hissing looks like pcb 01 in the Transmitter 1 may cause the problem and has to be replaced.

Pat

Thanks Pat

 

I did that and the sound works perfectly. I've tried using a Sonos with its variablr Toslink out and that works OK too. However, I want the Audiolab sound qualiry and 24k Hi Res decoding and for that I need the Audiolab preamp output. I have updated the Beolab firmware. I have tried to update the Transmitter 1 to make it always on and it will not accept the change. I am also unable to change the Transmitter 1 RCA gain from its preset -3 point. Could changing the RCA gain and/or the Input Impedance from High to Low work? However, when I follow the instructions the Transmitter 1 will not accept the changes.

FYI, I have worked out that you have to change the Transmitter 1 settings one setting at a time, such as:

;WPL-TX (svn:5309) Current Settings:RCA and TOSLink gain:-6

Great, is it ok now?

All working perfectly now and sounds great!

I have changed the RCA gain from -3 Db to -5 Db .

I have also changed the RCA trigger value to 100, the always on to true and the imput impedance to high. I suspect that it is the RCA gain change alone that has fixed the hissing problem. I will have a go at changing the imput impedance to back to low and the always on to false and see if that makes any difference; will report back.

Now I'm happy!

In this manual you have the USB way of changing TR1 parameters:

https://www.manualslib.com/manual/931303/Bang-And-Olufsen-Beolab-Transmitter-1.html?page=24#manual

Thanks mbolo01, I'll give it a go and let you know how I get on