PMFoundations Attenuverter User manual

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Attenuverter V1.0 –Assembly Guide
Thank you for purchasing this module! This is an easy build but with some surface mount parts
including precision integrated circuits. Some of the pads are quite small and you will need a chisel
tip or screwdriver tip soldering iron, fine solder and the skill to solder these tiny joints. If you have
not soldered SMD before, we recommend watching some of the many YouTube guides. Our
favorite: EEVBlog.
The module is designed and sized for Eurorack systems. You will need a 16-10 pin eurorack power
ribbon connector with –12/0/+12 which is connected to a synth power supply.
Follow the parts lists, these instructions and the PCB silkscreen text to build the module.
Please ensure that you place the components on the correct side. There are components installed
on BOTH SIDES of the board.

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1. A note on parts
We recommend 4.7k to 5.1k for the offset resistors. The amount of gain and inversion will vary
depending on the tolerance of these parts and the potentiometers intalled. 5.1k will ensure a
tiny amount of attenuation at full CW of the controls. 4.7k will give a slight signal gain at full CW
and 4.99k should provide an approximately 0db gain at full CW. You can use other values to
obtain varying responses from the controls.
You can even use different values for each channel to give you a versatile solution for
experimentation during patches.
10k Linear pots are recommended to get the 0 output at the center of the pot travel. You can
also use log/audio pots if you have them and the response will be slightly biased towards
inversion so that there will be more range on the CCW side of center than the CW side. You can
use 100k pots to obtain gain at CW rotation and a small amount of inversion at the CCW
position.
Feel free to experiment but use small amounts of solder so that you can make changes if
necessary until finalizing your desired component values.
2. Board preparation
Apply flux to the SMD pads. Tin one pad of each SMD footprint with a SMALL amount of solder.
For the ICs, apply a tiny amount of solder to two opposite corner pins.

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3. 1206 Size Resistors and ceramic capacitors
Install the 1206 resistors and 1206 capacitors on the TOP of the board by positioning on the
footprint and heating the cap and tinned pad until the part is attached. When all 1206 parts
have been attached. Solder the opposite pad of each part. Finally, reheat and add solder if
necessary to finalize the first pad of each part.
4. IC
Install the IC with the correct orientation. Align the dot/line or other marker with the
corresponding mark on the board. If you solder the ICs the wrong way round, they will explode
and render the board useless when power is connected. Position on the footprint and heat the
pin and tinned pad in one corner until the part is attached. Position and heat the pin and tinned
pad in the opposite corner until the part is attached and aligned with all pins and pads. Solder
the remaining pins and pads. Finally reheat and add solder if necessary to finalize the corner
pads of each part. Check for and remove any bridges between pins.

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5. Power socket
Install the 10 pin power socket on the TOP of the board. This must be installed with the correct
orientation or the module will be damaged when the power is connected.
The cut-out in the socket should face the jacks, aligning the cut-out with the "10" marking on
the board as shown in the photo. Solder on the underside.
6. Electrolytic capacitors
These are through hole components.
Install these on the TOP. Make sure you orient these capacitors correctly. The longer lead
and/or the lead marked with a + needs to be inserted into the hole that has the “+” marking
near it. Leads marked with “-“ go in the board hole WITHOUT the “+”. Solder and clip the leads.

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7. Potentiometers
If the pots have positioning lugs on the front, cut these off with a sharp pair of flush cutting
pliers. The front of the pot (where the shaft protrudes) needs to be flat.
Install 4 pots (10K) on the BOTTOM of the board.
Carefully align the pots so they are flush with the edge of the board and perfectly upright and
tight to the board surface. Solder one pin only. These will be finalized later. Please ensure they
are on the CORRECT SIDE OF THE BOARD. See Photo.
8. 3.5mm Jack Sockets
These are installed on the top of the board. Tack one pin only with solder. These will be
finalized later. Please ensure they are on the CORRECT SIDE OF THE BOARD. See Photo.

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Final Assembly
1. Place the front panel over the board so that the 3.5mm jacks align with the holes in the panel.
2. Put nuts on the jacks and FULLY TIGTEN all of them. Do not overtighten!
3. Now fully solder as many of the remaining pins on the jacks and pots that you can access
without burning nearby components.
4. Now remove the panel and finish soldering the more difficult to reach pins.
5. Put washers on the pots and place the front panel over the PCB again so that the pots, switches
and 3.5mm jacks align with the holes in the panel.
6. Put nuts on the pots and jacks and FULLY TIGTEN all of them. Do not overtighten!

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7. Calibration:
a. connect the power and run a fixed voltage of +5 to +10V into the first input.
b. Without changing the input voltage, monitor the voltage from the output jack with a
multimeter.
c. Adjust the pot shaft until you read 0V on the multimeter.
d. Place the knob on the pot shaft so that the pointer points to 0 on the panel.
e. If you do not have a meter, you can put an audio signal into the input instead of a DC
voltage and listen to the output and adjust the pot until the output can not be heard
and then install the knob.
8. Repeat step 7 for the remaining 3 channels.