Suede·Social
Power supplies·2026 · OCT
Isolated outputs2700mA DC6V · 9V · 12V · 15V · 18V

01MXR · jack-by-jack math

How many pedals can the MXR ISO-Brick M238 power?

10 isolated outputs and 2700mA of DC, checked jack by jack against 211 pedals at their own voltage.

Plan a board on the MXR ISO-Brick M238

02The short answer

Up to 10 pedals, one per output (2 of them 18V only), from 2700mA of DC.

Built for: A ten-pedal board with mixed voltages: two dedicated 18V jacks, two variable 6V to 15V jacks, and two 450mA jacks for the biggest 9V pedals.

  • 153 of the 205 powered pedals in our database run on any jack here at their voltage, even its smallest (100mA at 9V).
  • 42 need one of its larger jacks, up to 450mA at 9V.
  • 6 draw more than its biggest 450mA jack.
  • 4 pedals have no published draw: read the figure off the label and the calculator finds the jack that carries it.
  • 4 passive volume pedals take no jack at all.
  • The Eventide H90 Harmonizer runs from its own 12V adapter, off the supply.
  • The Electro-Harmonix Deluxe Memory Man runs from its own 24V adapter, off the supply.

03The jacks

Per-jack ratings as the manufacturer publishes them. A jack carries a pedal when it offers the pedal's voltage and its rating at that voltage is at or above the pedal's draw.

OutputJacksVoltagemA per jackPedals each jack carries
Jacks 1-229V100mA148 of 201
Jacks 3-429V300mA185 of 201
Jacks 5-629V450mA190 of 201
Jacks 7-8218V250mA5 of 201
Jacks 9-1026V / 9V / 12V / 15V250mA173 of 201
Total DC102700mA

Every output section is isolated, so a digital pedal on one jack does not share a ground with the pedal next to it. “Pedals each jack carries” counts the 201 powered pedals in our database with a published draw, each at its own voltage. Pedal figures are typical published draws; check each pedal’s label for its voltage and polarity before you plug in.

04Where the big pedals go

The pedals in our database that need more than its smallest jack at their voltage, highest draw first.

Needs a larger jack · 42
Not on this supply · 6

Run these from a supply with a bigger jack. Compare supplies.

05A real board on it

The calculator's example board (a tuner, a compressor, an overdrive, a distortion, a delay and a reverb), run on this supply.

Runs clean

Draw
293mA
Available
2700mA
Headroom
2407mA
Outputs
6 of 10

Open it in the calculator

Source

Per-jack ratings transcribed from MXR’s published spec. Outputs 9 and 10 are continuously variable from 6V to 15V; the listed voltages are the common taps. MXR spec page.

Maker figure, unverified.

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