What you want is:
With isolated outputs, you can get Y cables to connect them to get the extra juice 9+9=18V
Or you really want the pooteek of pootek:
The FLATLINER!!!!!!!
MFING FEATURING:
Standard 9V
Flatliner has 8 DC outputs for the use of 5.5x2.5 mm barrel connectors (Boss-type).
12 VDC
Some effects need higher voltages. Examples are: Boss ACA-type effects, made before august 1997 need 12VDC for proper function. You can connect these effects to the 12V DC outputs of the Flatliner. All Boss PSA types and post-august 1997 ACA effects you can connect to the 9VDC outputs.
18V/24VDC
Because all outputs are isolated it is possible to join two 9VDC or 12 VDC outputs in a serial connection to double the voltage to 18 or 24 VDC or a parallel connection to double the current to 400mA.
9/12 VAC
Most tubedriven pedal need AC power. Flatliner V 2.0 can be configured to 12 VAC, in stead of standard 9VAC. The Line 6 PODs need 9VAC output. The Line 6 modelling pedals can be powered through the 9VDC (MM4, FM4) or 12VDC (DM4,DL4) outputs. Since these effects draw more current (150-185 mA) than average you can connect one effect with one output. The Flatliner can power several Line 6 effects simultanously. Note: Line 6 modelling effects have reversed polarity. Use the right cable.
Dying battery OMG SIMULATE BATTERY SAGS
This option gives creative guitarists the opportunity to simulate the special effect that an almost empty battery causes in some fuzz and overdrive effects. The Flatliner's dying battery option provides variable voltages from 3-9V and 3-12V, this in combination with variable output resistances, to achieve the right mix.
Y CABLES COME IN SERIES AND PARALLEL: