[Xanthos]

Hello all,

My newly arrived MPX3 has developed a rather odd noise problem. Any time the table the amp is sitting on vibrates slightly, the amp makes a low thumping noise. This also happens when the amp itself is tapped on slightly. It also hums every once in a while if left on for an extended period. This hum comes and goes making it hard to track down. Has anyone else experienced these two issues and specifically is this thumping noise normal when it is tapped?

 

[grawk]

Give mikhail a call, he'll help you figure out what's wrong and make it right.

 

[Hirsch]

Thumping when tapped is a microphonic tube. Replace the tube with a non-microphonic one, and the problem should be gone. The microphonic tube is likely to be the source of the noise issue as well.

 

[Duc]

Yeah, it sounds like a microphonic tube. You can try swapping the left and right channel tubes and see if the noise follows the tube over to the right channel. You will get a thump or ting when tapping on the amp, some tubes are worse than others. I'd contact SinglePower if it presists as an issue.

 

[nikongod]

it could also be the gain tube which is microphonic. this could effect either channel separately, or both. so check on it too.

hearing the symptoms you describe, it is almost certainly a microphonic tube somewhere. tube dampers might help A LITTLE, but dont expect a miracle.

 

[lator]

It is a microphonic tube allright. Driver tube section seems to be pickier about the tube you put in. For example while using the very tube that causes microphonics at driver section does not cause microphonics at output section (or at least not nearly as much).