18v out of a 19.5v laptop power brick

[DavenPaget]

Don't be so confused about -9v . It's just wired differently if i recall .
IF i'm not wrong it's center-positive . ( which happens to be ground ... )

[runmikeyrun]

dont let a laptop supply scare you off... I use one on my Quadcaster at 12v and it's quiet as a mouse.  I use a "traditional" 12v wall wart from an old router, which you would think would be quiet, but it makes all kinds of noise on any valvy I plug it into.  Just have to try it and see.  The nice thing about laptop supplies is they can put out a lot of current, which is good for powering tube stuff with multiple tubes.

[DavenPaget]

dont let a laptop supply scare you off... I use one on my Quadcaster at 12v and it's quiet as a mouse.  I use a "traditional" 12v wall wart from an old router, which you would think would be quiet, but it makes all kinds of noise on any valvy I plug it into.  Just have to try it and see.  The nice thing about laptop supplies is they can put out a lot of current, which is good for powering tube stuff with multiple tubes.

Laptop supplies are quiet especially those designed for stuff that has to do video and audio .
Obviously it has to be unless some spiffy monolithic filters going on in the DC-DC Converter section , but we must remember that DC-DC converters doesn't work very well with noise/poor filtering from the brick .
Well , the only silent router supplies i came across from Leader Elec are from Linksys New 'E' series routers , they are silent as a mouse although it has a 500mA rating only but IV Efficiency label .
Haven't tested 2 modem power supplies from Leader too , they're for motorola broadband modems ... Hmm .