Mixer troubles and attachment progress

As mentioned in the post before, jumper wires were soldered to all audio jacks in order to test the splitter and mixer by simulating two FX loops. As stereo jacks had been bought, it was important to solder the wires to the correct parts on the audio jacks to make them work with mono TS guitar cables. With the audio jacks sorted, the FX loops were then simulated by leaving one signal dry and putting a booster in the second signal chain. If the signal got louder, the FX loops should work as expected. Unfortunately, the circuits were not perfect yet. While both circuits, that of the splitter and that of the mixer seem to work fine on their own, they produced a very loud humming noise leaving the guitar signal barely audible. Sometimes it did not work at all.

Before Christmas, the project’s supervisor was consulted, and he provided a picture of the same mixer circuit that he recreated for some other project. Using this picture as a guidance, the mixer circuit was tackled again. Additionally, a bigger breadboard was bought to better accommodate the circuit. Nevertheless, the mixer’s performance did not improve a lot. While it seems to work, the humming noise is still very present making it unsuitable for further use within the project. As of now, the splitter/mixer components of the hardware switch are not working and a solution for this major problem must be found.

Another challenge was to find a solution for the attachment of the ToF sensor of the left hand setup. As already mentioned, the attachment device should be flexible enough to fit onto both, Fender headstocks as well as Gibson headstocks, the two most common headstock shapes in the guitar world. The first idea was to use a swan-neck and some type of table clamp and said parts were ordered. Upon delivery however, it was clear that the table clamp was way too big and heavy for the comparatively fragile guitar headstock. Additionally, the swan-neck proved to be too short and too inflexible so the sensor could not be positioned correctly. Afterwards, a swan-neck lamp by IKEA was tested. It was more lightweight and flexible enough to position the sensor correctly. However, it was not stable enough and changed its alignment with every move of the guitar. This, of course, made rendered it impossible to be used as an attachment device. There was more luck to be found with the third possible solution, a device consisting of a clamp and a semi-flexible arm with joints originally made to hold a GoPro. The clamp was small enough to fit onto guitar headstocks. The arm was flexible enough to position the sensor in the way required for a Fender headstock and a Gibson-type headstock. At the same time, it proved sturdy enough to hold its position while moving. A small setback happened that could be sorted out quickly: for testing a different (but very similar) ToF sensor of the type VL53L0X was used that could not detect the frets as accurately as the original ToF sensor. Worried that the new attachment device required major changes in the Arduino code of the ToF sensor, the original VL53L1X sensor was used. Luckily, it worked fine and could detect the frets as accurately as with the old attachment device. Just to be sure, another VL53L1X sensor was ordered as a back-up.

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