Lower power on left channel

I had that problem a few weeks ago and it was the right channel with my pre amp that was causing the problem so I replaced it and all is good as new.

Good luck, OP!

Seasons greetings to you Bigred,

just a quick fyi that Prima Luna amps are equipped with a “BTI”  (bad tube indicator).  It’s an LED that will glow red located in front of each power tube.  If no red LED glow your tubes are good to go. 
 

Enjoy the music. 

I’d work back from the speakers. Swap the speaker cables at the back of the amp. If the trouble follows the swap, you’ve ruled out your speakers. Swap the cables back.

Next swap the cables from the preamp. If the trouble moves, it’s the preamp or source. Swap the cables back.

Swap the cables from your source. (CD, DAC, etc). If the trouble moves, it’s your source. If it doesn’t, you’ve ruled out everything else and it’s your amp. Swap the cables back.

Now you can start swapping tubes around with some confidence to help pinpoint things. If tube swapping doesn’t make any difference then you have another issue with your amp and unless you’re well versed, you might need to seek professional assistance.

Almost my entire career was in IT, both hardware and software. The trick to this kind of troubleshooting is no trick at all. It’s being methodical and thinking the problem through. Best of luck!

Happy listening.

Hi Guy's

I have not checked the red light (bad tube indicator) I did not notice that any of them where on when leaning over the amp checking the heat of the tubes before turning the amp off, I will have to power the amp and check at the same time as changing the speaker cables over. Source wise, I have  tried change the input on the pre amp from Dac to phono pre amp, that did not make any difference.