gbo noise with external power supply

[Suicicoo]

hi there
i recently bought a power supply for my gbo and today i wanted to try it... gameboy working fine, but theres a weird noise when turning it on - its only with the power supply, batteries are fine - the power supply is switched to 6 volts, center negative(doesnt work the other way round, ive tried...)
has anyone else already experienced(and hopefully solved) this problem?
thanks in advance - sui

[Gunk]

which power supply are you using btw? model, brand etc.

[Suicicoo]

its a 10€- 'profitec'(german company) ''Universal Power Supply - 1000mA regulated AC/DC Adaptor'' it puts out 800mA for 6V
any more info needed?

[palmertech]

It is just not a well filtered/regulated power supply, so it introduces the noise from AC. The only way to fix it is to get a better power supply, or run off batteries.