That is strange. There doesn't seem to be any switches or volume control on the Logitech to complicate things - it's just a straight-through receiver. I take it there is zero music sound appearing at all - no matter how quiet - when connected to the Quad pre amp?
It suggests only several options, all fairly unlikely in isolation:
1. The Bluetooth signal is not being received when the Logitech is in the lounge. I think the manual says the blue light will be on if a connection is established to the computer. So is the blue light on when in the lounge?
2. The RCA outputs of the Logitech are faulty
3. The interconnect cable broke suddenly
I assume when working with the computer speakers that the 3.5mm output on the Logitech was being used rather than the RCA outputs?
When the Logitech is in the lounge, do you have anything that you could plug into its 3.5mm socket e.g. a pair of headphones? Or temporary move the computer speakers to the lounge. That would rule out the first option above.
The blue light on the Logitech is on but nothing coming through headphones. distance from Hi-fi to computer is ~20 ft if that. I will wait and see if the 'new' connector sent up with my new CD helps. Meanwhile many thanks for all your help and suggestions.
If you get no joy with the new connector it may well be that the Logitech isn't up to the job. Whilst Bluetooth should be good for distances up to ~30 feet this may be reduced due to obstacles, walls and interference from other RF signals. Whilst the Logitech works well over short distances reviews suggest it can be noisy where the signal quality is poor.
You may have more success with the more sensitive (and much better performing) IFi ZEN Bluetooth receiver which is very well regarded.