Strange things happening with Audiolab 8000A

Mr Lime

Distinguished Member
I have an Audiolab 8000A amplifier. I use it for my CD, radio tuner and mini disc deck listening. I also use it for films to drive the front L-R channels in my surround sound system by running the front L-R pre-outs from My AV amp to the Audiolab.

While watching a film tonight I noticed a thumping that was coming from the right hand speaker. It was a sound similar to what you sometimes hear when your subwoofer switches on. At first I thought it was in the film, but when I rewound and played the same scene again - no thumping sound.

I noticed then that the thumps were recurring occasionally.

I switched of the AV amp and Blu-Ray player and tried some of the other inputs:

CD - nothing
Radio tuner - only right channel working
Mini Disc-both channels working, but suddenly left channel disappeared.

Then here's where the strange stuff started happening.

I switched the amp off for about 20 minutes, turned it back on and all the aforementioned inputs were working fine on both channels, but with still the occasional thud from the right hand speaker.

I switched off all the input sources, but before I turned off the amp off, I noticed a thump still coming from the right speaker while all sources plus the AV amp were powered down.

Help? 😦
 

noiseboy72

Distinguished Member
Sounds like a problem with the pre-amp section passing a DC component through to the power amp. I would not use it and get it to a repair shop before you damage your speakers or the amplifier any further.
 

oscroft

Member
Sounds like a problem with the pre-amp section passing a DC component through to the power amp. I would not use it and get it to a repair shop before you damage your speakers or the amplifier any further.
Could be. The 8000A power amp section is DC-coupled from input to output. There is decoupling at a couple of points in the pre-amp section, but the decoupling capacitors could be failing and becoming electrically leaky. In my view, most 8000As really need recapping now, as they're getting a bit old. I found quite a few caps out of spec with mine, one or two of them very leaky and probably not far away from shorting.

(Of course, there could be other failing components causing it - there's no way to tell from the description of the fault).
 

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