Channel unbalance with Primaluna Two

Hi,

I've just discovered a serious problem with my Prologue Two.
I have an analogue setup using a Rega Planar 3 as the source. I was testing my anti-skating setting on the tonearm with "Hi-Fi News Test LP" track no 6 (300 Hz signal at 12dB). I had a multimeter on each speaker's terminals. One the right channel I read 100 mV, on the other 80 mV (multimeters are Fluke, good brand, not a toy). I tried to work it out with the anti skating knob on the tonearm, but I couldn't.
I swapped over the speaker cables, and again the right channel was louder. That told me that something is wrong with the Prologue.
I also have a solid state amp, I swapped over: left channel 99 mV, right channel 100 mV.
Using the Prologue the difference between the two channels is big: 20%. I can hear that the soundstage is pushed out to the louder (right) speaker.
I swapped all of the tubes from left to right but the problem remained on the same channel.
I am really stucked here... Get new sets of tubes or return the amp for repair?
Does anybody knows the solution?

Thanks

 

If you've swapped the tubes over and the problem remains then you have an ampllifier fault and it should be returned/serviced.

Unless you are confident performing diagnostics of valve circuits I wouldn't attempt a DIY repair due to the high voltages flying around.

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