kilter build manual

kilter is a surface mount build involving 0603 passives and several TSSOP ICs. While it can be assembled entirely by hand, reflow soldering is highly recommended and is the method used in this guide. A microscope is also very helpful if you have poor vision like me.

NOTE: this manual is for the full surface mount kit, which will not be supported in the future

This manual assumes you have a kit with everything listed here.

Before starting, ensure you have the following tools:

  • ESD safe tweezers
  • Solder paste (room temperature)
  • Reflow oven or hot air station
  • Optional (but recommended):
    • Stencil and squeegee
    • Isopropyl alcohol
    • Soldering iron
    • Solder
    • Wick
    • Flux
    • Microscope

0. Read this guide in full

Make sure you understand the overall process and have sufficient time set aside for each step. Once the solder paste has been applied, you have a limited window in which to place your parts and reflow the board.

That being said, take breaks, even when placing components. It depends on your solder paste, but several hours should be completely safe.

1. Review BOM

Confirm that you have everything listed in the BOM. If you received a kit from me and notice anything missing, let me know.

NOTE: an interactive BOM is available here to simplify assembly.

2. Apply solder paste

You will need:

  • kilter PCB
  • Solder paste
  • Isopropyl alcohol
  • Stencil

Clean the PCB with alcohol, align the stencil, and apply the solder paste. If you are unfamiliar with the process, this guide is a good introduction. If you're not using a stencil but still want to use solder paste, you can try applying it with this method. It can be tedious, but it works.

Remove the stencil carefully and clean any residual paste off with more alcohol before setting it aside.

3. Place passives

You will need:

  • 0603 resistors and capacitors
  • Electrolytic capacitors
  • 0603 Ferrite beads

Work your way down the BOM, placing all resistors, capacitors, and ferrites with tweezers. They don't have to be perfectly aligned. Surface tension will pull most misaligned parts into place once the paste melts.

4. Place active components

You will need:

  • SOT-23 transistor (BC858)
  • SOT-363 transistor pair (BCM857BS)
  • SOT-23 5V voltage reference (LM4040C5)

Place the transistors and the voltage reference.

Be careful: The voltage reference and the single transistor have the same package. Don't mix them up.

5. Place integrated circuits

You will need:

  • TSSOP op amps (TL072 and TL074)
  • SOIC OTAs (LM13700)

Finally, place the integrated circuits. The OTAs are fairly forgiving due to their larger footprint, but the TSSOP op amps must be carefully aligned with their pads. If you have a microscope, use it for these.

Be careful: Don't push down on the TSSOP chips. If the leads bend or the solder paste is spread out too much, they will be extremely difficult to fix.

6. Reflow

You will need:

  • Board with all surface mount components placed
  • Reflow oven or hot air station

Using your preferred workflow and tools, reflow the board and ensure all paste melts.

6.5 Take a break

You will need:

  • Nothing

You've earned it. The time sensitive part is over, and until you inspect the board you can pretend everything went perfectly and relax for a bit!

7. Surface mount inspection

You will need:

  • Reflowed board
  • Tweezers
  • Rework tools (either a hot air station or a soldering iron with flux and wick)
  • Microscope (recommended)

Inspect each component under a microscope after to ensure there are no misaligned pads or bridged connections. If there are, use tweezers with hot air or a soldering iron with plenty of flux to fix them.

Pay particular attention to the TSSOP op amps. There should be no solder bridges between the pins, but you may notice traces connecting the following pins which can be safely ignored:

TODO: images

8. Through hole components

You will need:

  • Soldering iron
  • Solder
  • Flux

Solder the first green LED and shrouded power header (make sure the key lines up with the silkscreen).

Carefully assemble the remaining panel components on the front side of the board with the panel attached to keep them aligned.

Flip the module over and solder the front panel components.

9. Final inspection

Inspect the board and ensure all solder joints are clean.

Using a multimeter, test the power rails. Ensure there are no shorts between ground, +12V, and -12V.

10. Smoke test

You will need:

  • A power supply isolated from your modular

Plug your module in and power it on. Ensure there is no smoke.

Assuming that worked, turn up the resonance and adjust the cutoff knob. You should notice some activity on the outputs from the filter self oscillating. Turn the resonance back down completely. There should be no LED activity.

If you notice anything unexpected, inspect the board again and ensure there are no solder bridges.

11. Calibration

You will need:

  • An oscilloscope (if you don't have one, you can use software such as Signalizer)
  • A V/Oct source
  • A chromatic tuner

Crossfader

Set up a scope with channel one on the bottom filter input and channel two on the low pass output.

Turn the mix and cutoff knobs fully clockwise and connect a square wave to the top input.

Turn the XFADE trimmer until the input matches the output. Then, turn the mix knob fully counter clockwise and ensure the output is silenced. Repeat and adjust trimmer as necessary.

Key tracking

Connect the V/Oct source to the CV2 input with a chosen starting note (e.g. middle C). Connect the low pass output to a tuner. Turn the resonance knob clockwise until it starts oscillating, then adjust the cutoff knob until the tuner displays the correct note. Sequence the same note across two or more octaves and adjust the TUNE trimmer until the tracking is as close as possible (it won't be perfect, but close is good enough).

Resonance

Turn the Q knob fully clockwise and the qdrive knob to its midpoint. Turn the frequency knob to its midpoint. Adjust the QFR trimmer counter clockwise until the green LED just turns off, then slightly turn it back until it just turns on.

To an extent this is based on preference, but if the trimmer is set too far clockwise it's very easy to hit rail to rail voltages with high resonance, potentially resulting in phase reversal with the TL07x op amps in the module. A lower resistance is recommended.

Notch

This one is also mostly preference and controls the depth of the notch. Set up an LFO on the cutoff frequency and pass some audio into the filter while listening to the notch output. Adjust the notch trimmer as desired. A low (mostly counter-clockwise) value is ideal.

12. Done

Congratulations and enjoy your new filter!