Aqvox problem with out put.

My Aqvox is driving me crazy. When listening to vinyl it starts out performing exceptionally well as it has for the past two years. Recently it started loosing output in the left channel. I initially thought it was a problem with the cartridge and change over to a different one. It played well for about an hour then the problem surfaced again. I tore everything a part all the way back to the speaker cables and carefully hooked everything back up again. It played well. The following week with friends over checking out some tunes about 45 minutes in to it the problem surfaced again. I switched immediately to digital and of course both channels played flawlessly. Switched back to vinyl and the left channel was completely dead. The following day I played the Aqcox for about an hour with out a problem. This weekend with more time for listening the same thing happened again about an hour in to it.
Has anyone had a similar experience? Any ideas what this could be? Let me know. I appreciate any feedback.
OK. I am from Thailand. I have experienced problems with the AQVOX MIC 2 A/D for two occasions around two years ago. First, the defect came from its power supply. The AQVOX company from Germany sent me a new power supply one for replacement then it worked fine for another one or two months. The second flaw due to internal component failure. I asked replacement of the power supply again but it didn't work. I had to sent all back to the company for fixing that took around two monthes before it came back now and still works fine without problem. I have a DAC USB MK2 which I bought before the A/D around 6 months. The DAC works fine unitil now without any flaws. Contact a service guy there in Germany at, he could help fixing the problem.