И буржуи пишут о таком трабле
http://www.harmonycentral.com/t5/Effects-Pedals-Multi-Effects-and/I-Just-Got-A-Zoom-MS-50G-MultiStomp-FX-pedal-99/td-p/34241195
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Now the bad news, there's a major flaw with the amp modeling in these units. On any amp model, there is a high frequency noise that occurs when the gain is turned up. The higher the gain, the higher the noise. Lowering the gain to nothing on any amp model does seem to get rid of the problem.
The same high frequency noise occurs on the 'Acoustic Sim' but instead of 'Gain' it's the 'Top' adjustment that cause the high frequency noise. Turn the 'Top' adjust clockwise, the high frequency noise increases. Turn the 'Top' all the way counter-clockwise and the noise goes away.
I have verified that the HF noise has been noticed by other MS-50G owners. I suspect this is a software problem that can be fixed by a firmware update. Part of the reason I think this is that none of the crunchy stomp box models have the same HF noise issue. So, the problem with gain is only happening with the amp models...including the 'Acoustic Sim' which probably uses the same software modeling engine as the amps.