Lower power on left channel

If your tube sockets are marked left and right you could swap the tubes. When you listen again if the low power sound moves to the right, it would be your tubes. Also check connections. I guess I would swap left and right speaker cables to further check these circuits in the same way. Good luck.

+1 @2psyop  .  I don't know your preamp, but I have a Cary SLP 05 that uses 6SN7s, and using a specific test tone on a test CD I have used the AC volts setting on my meter to check volts at my speaker terminals, and I have found that depending upon which tubes I am using in my balanced input sockets, the readings are not always the same from L to R speaker.  I have found that when I then swap my L & R balanced input tubes, the readings I get follow the tubes.  

When I can get to the back of the amp I am going to change the speaker cables over and see if the loss of power is then on the right hand channel.

Good plan.  If it doesn't follow the speaker cables, I guess it's the speakers.  If it does follow the speaker cables, try swapping pre to amp interconnects, and if it follows them I guess it's in the preamp, and if it doesn't, I guess it's in the amp.

Good luck.

It's almost certainly a tube or tube going bad you have some good advice above.

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.    

Addendum to my previous response-I have a non contact infrared laser pistol grip thermometer that has many uses.  Just added checking Amp tube temps to it's portfolio.  Got it at HF (20:1 ratio for less than $40 with coupon) originally to check header pipe temps on engines..  Very accurate on tubes also.

@bigred71 

 before you swap the wires, swap the tubes. Wires rarely go bad, but tubes often do.

All the best.

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