Doepfer

Hello

I assume you mean a mechanical hum. Right?  If so, then it should be 
related to the method how the powersupply is fixed to the housing.

Florian


On 07.07.13 00:31 , isoldeandisobelle wrote:
> Hi gang -
>
> I have a 6U case and a 9U case, the 9U PSU hums (which changes in frequency when different modules are in use.) - the 6U does not do this.... is this ok?
>
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