Rabid Elephant Mr. Black Eterna User manual

© 2013 Rabid Elephant
Page 1 of 4
DOCUMENT VERSION:1V0
LAST EDITED 7.16.2013
www.rabidelephant.com
[e-mail]
The Rabid Elephant recognizes his reflection…
Disclaimer: Rabid Elephant is not responsible for damage to MidiBrains or
your property in any way. We are also not responsible for injury or death
resulting from the use or installation of MidiBrains.
Do not attempt installation of MidiBrains unless you are trained and
comfortable working with electronics.
1INTRODUCTION
This guide outlines the steps required to install the Rabid
Elephant MidiBrains 2v1 MIDI interface board into a Mr. Black
Eterna reverb pedal.
MidiBrains is easy to install but some pedals require special
considerations depending on the effect circuit. If you are
installing MidiBrains yourself, please make sure you
understand how MidiBrains likes to be connected before diving
in.
MidiBrains uses 2 mm pitch dual-row connectors for all
connections to the MidiBrains board. Your kit comes with pre-
crimped wire harnesses. Use them. The MidiBrains headers
are labeled on the PCB.
Installation time is approximately 2.5 hours if you are
thorough, take your time, and check your work.For any
desoldering and cleaning out pads, we find the best tool is
decent quality #2 solder wick. Also ensure a static-safe work
environment throughout the installation process.
The installation should resemble Figure 1 when finished.
Figure 1. What the wiring should resemble when you are
done.
Please note that modification of MidiBrains into the Eterna
requires cutting PCB traces since everything on the Eterna is
PCB mount. MidiBrains always retains at least the stock
functionality of the devices it’s installed so it’s not a big deal.
2DISASSEMBLY
Remove power from the Mr. Black Eterna before proceeding.
Remove the 4 screws on the back of the Eterna and remove the
cover.
2.1 REMOVING THE PCB
Remove the knobs by loosening the setscrews.
Remove pot, jack, and switch nuts as shown in Figure 2 to
allow removal of the PCB. We will be using the stock switch
– leave it installed.
Figure 2. Nuts off.
The PCB is now be free and can be removed from the
enclosure as shown in Figure 3.
Figure 3. The PCB has been removed.
3PCB MODIFICATIONS
You will need a needle file (with a sharp cutting edge on its
side – like a half-round or some shiz) to cut through several

© 2013 Rabid Elephant
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traces on the Eterna PCB. These are located on the top of the
PCB in the gap between the switch and jacks. The needle file
works great. If you ask again, well, it’s your life so do what
you want :D Figure 4 shows where the needle file should go.
Figure 4. File that shizzle.
Carefully cut through the first 5 traces (from the left of the PCB
(the side with the ground spring (that’s some top notch
engineering, there, Mr. Black) (oooh, nested parenthesis))) as
shown in Figure 5. Do not cut too deep into the PCB; the traces
are only about 40um thick. You are crazy for doing this,
maybe. Either way, the Rabid Elephant is proud.
Figure 5. Look at my crazy good filing skills.
Now remove R14.
That’s it!
4INSTALLING AND WIRING UP THE MIDI
MidiBrains requires at least a MIDI In jack to be able to receive
MIDI data. Adding a MIDI Thru jack will allow daisy chaining
of multiple MIDI devices across your pedals, which is
extremely convenient and far more compact than using MIDI
DIN connectors. It is recommended you add the MIDI Thru
jack.
Also note that this procedure mounts the MIDI connectivity to
the pedal using additional jacks, which requires drilling two
holes in the pedal somewhere. If you do not wish to drill these
holes in the pedal, you can run one or two (if you want MIDI
Thru) female 3.5mm cables out of the bottom of the pedal and
leave the bottom cover cracked.
4.1 INSTALLING THE MIDI JACKS
Drill a 6mm (15/64”) hole on the input side the enclosure
40.5mm from the outside of the top edge and 10.5mm from
the bottom edge of the pedal (without the cover) for the MIDI
Thru jack. Drill a 2nd 5/16” hole 40.5mm from the outside of
the top edge and 20mm from the bottom edge of the pedal for
the MIDI In jack. The MIDI In jack is the isolated one – you
must install this jack in the hole before soldering on the wires.
I always screw this up for some reason. Noob. It will look
like Figure 6.
Figure 6. Get dem holez.
You may find other locations the jacks will fit. Be certain
there is no possibility of the back of the jack shorting
something out or colliding with other components.
4.2 WIRING UP THE MIDI JACKS
4.2.1 MIDI IN
Connect MidiBrains MIDI IN/THRU Header P1 (ORG) to
MIDI IN 3.5 mm jack ring (gold terminal).
Connect MidiBrains MIDI IN/THRU Header P3 (WHT) to
MIDI IN 3.5 mm jack tip (silver terminal).
4.2.2 MIDI THRU
Connect MidiBrains MIDI IN/THRU Header P2 (YEL) to
MIDI THRU 3.5 mm jack tip (silver terminal).
Connect MidiBrains MIDI IN/THRU Header P4 (PPL) to
MIDI THRU 3.5 mm jack ring (gold terminal).
Filed.

© 2013 Rabid Elephant
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Connect MidiBrains MIDI IN/THRU Header P6 (BLK) to
MIDI THRU 3.5 mm jack sleeve (long terminal).
For the provided barrel 3.5 mm jacks, the long terminal is
sleeve, gold terminal is ring, the silver color is the tip. The
colors may be off (who knows…) - always double check with
a multimeter. When you’re done it should look like Figure 7.
Figure 7. MIDI jacks wired up.
Please note that to follow the MIDI spec (and to avoid
ground loops), the MIDI In jack must be isolated from chassis
ground. If you use a metal jack and don’t isolate it from the
device chassis, you must make sure your cable’s shield (MIDI
DIN connection Pin 2) is broken at this end. If you make a
cable like this, make sure you respect the cable direction and
mark the cable accordingly.
The MIDI Thru jack shield should be connected to chassis
ground. Metal jacks are used on the MIDI Thru.
5WIRING UP THE LED
Solder the MidiBrains AUX P3 (BLUE) to the LED anode pin
directly as shown in Figure 8. Connect the MidiBrains AUX P6
(BLK) to the LED kathode pin.
Figure 8. You will come back to this picture often,
methinks.
6WIRING UP THE FOOTSWITCH
The Eterna footswitch is alternate-action so make sure the
firmware of your MidiBrains is correct! You specify the
footswitch type when ordering.
Connect the FS/MIDI OUT Header P4 (BLUE) to the switch
pad as shown in Figure 8. It’s the top right pad of the
footswitch when the pedal bottom is down. Ground is already
provided.
7WIRING UP THE RELAY
The Eterna uses an input shunted, current limited true bypass
approach to reduce switch pop. It is wired a little differently
than a ‘standard’ true bypass circuit. To accommodate this and
keep the pedal operating as it was designed, carefully desolder
and remove the R20 jumper on the MidiBrains PCB. Jump P3
to P6 on the MidiBrains Relay Header as shown in Figure 9.
Figure 9. Jump pins 3 to 6 on the 'Relay' header.
Now make the following connections:
Connect MidiBrains RELAY Header P2 (WHT) to location ‘Ein’
in Figure 8.
Connect MidiBrains RELAY Header P1 (GRN) to location ‘Jout’
in Figure 8.
Connect MidiBrains RELAY Header P6 (ORG) to location ‘Jin’
Connect MidiBrains RELAY Header P5 (BLU) to location ‘Eout’
Connect MidiBrains RELAY Header P4 (color varies) to GND.
8POWER
Remove the 9V battery connector – you wont need it.
Connect MidiBrains PWR IN Header P1 (RED) to the DC jack
sleeve pad on the Eterna as shown in Figure 10.
Connect MidiBrains PWR IN Header P4 (BLK) to ground on
the DC jack tip pad of the Eterna as shown in Figure 10.
Jin
Eout
Ein
Jout
GND
JMP

© 2013 Rabid Elephant
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Figure 10. Power connections.
Please also note that some effects can accept a wide range of
input voltages. If you want MidiBrains usable for higher
voltages (above 12V), you must add a series resistor in line with
the PWR IN P1 (RED) wire to take some of the thermal load off
the onboard regulator. MidiBrains draws 50mA max – design
for this figure (it’s a linear 5V reg).
9TESTING MIDIBRAINS
Go over your work. If it all is correct, connect a ¼” plug into
the input (if you don’t do this, some devices will not receive
any power), apply power to the pedal, and see if the LED
blinks on power-up. If it doesn’t, immediately turn power off
and check your work again.
If all is good, check the footswitch toggles the state of the pedal
and the LED turns on/off (you have to wait 1 second past
power-up, else a footswitch press puts you in setup mode).
Now plug in some MIDI to the MIDI In jack from your MIDI
source (interface, MIDI controller, etc…) and send it a PC000
MIDI message on MIDI Channel 10. This is the factory default
PC and MIDI Channel. The LED should be off for PC000. Now
send it PC001 – the effect should now be enabled and the LED
should light up. In run mode, the LED will blink quickly upon
receiving the correct PC message on the correct MIDI channel.
Note that you can change the MIDI Channel and PC messages
MidiBrains responds to using setup mode as described in the
user’s manual.
10 MOUNTING MIDIBRAINS
MidiBrains is typically mounted in the 9V battery compartment
of your pedal using a special U-channel clip that MidiBrains
slides into.The battery compartment is the only location in the
Eterna where MidiBrains will fit.
Attach the PCB clip and insert MidiBrains into the battery
compartment of the pedal. Make sure the cover will fit without
pushing any components or cables when screwed in. You may
have to carefully rout the wiring around certain components.
We add a few dabs of hot-melt glue to secure the wiring to the
PCB.
I think that’s it… Bye!