synth diy

Description: Some components for the equalizer (EQ) are mounted on the potentiometers. The only modifications made to the circuit from the previously posted schematic include the addition of a feedback loop from the line output to the switched side of the first input jack. This configuration ensures that the connection is severed when another device is plugged in. The feedback loop enables the EQ to function as a sound source independently, even without any external inputs. Although initially not planned, the MC4024 voltage-controlled oscillator (VCO) was added to the project. The available space on the board was utilized to incorporate a 4015 shift register pair as well. The 4015 was sourced from a second-hand store and features a transparent plastic casing, allowing for visibility of some resistors on the circuit board, which indicated potential pitch control functionality. The resistor identified as R2 is the pitch resistor. The circuit also includes a built-in speaker. The sound-generating component is a blob-type integrated circuit (IC). An alternative modification considered was to add external play triggering; however, retriggering during playback did not interrupt the ongoing sound, making it less appealing. The final modification involved removing the original resistor and replacing it with a 10k resistor (the original was 55k), in addition to integrating a 500k potentiometer in series. After modifications, a second 10k resistor was added to the opposite side of the potentiometer, as the initial 10k was insufficient to prevent the chip from crashing, which could be resolved by cycling the power. Touch points were also added using screws for pitch adjustments, which occasionally resulted in glitching or crashes, again easily rectified by cycling the power. An output jack was incorporated with a 1k resistor at the board end of the wire; a 1/8 inch jack was selected due to size constraints imposed by the enclosure. Some plastic was ground away to accommodate the jack.

The circuit described integrates multiple functionalities centered around an equalizer and sound generation. The feedback loop implemented enhances the versatility of the EQ, allowing it to produce sound autonomously. The addition of the MC4024 VCO broadens its capabilities, facilitating modulation and pitch variation. The incorporation of the 4015 shift register allows for more complex signal processing, potentially enabling the creation of rhythmic patterns or sequenced sounds.

The modifications made to the pitch control involve careful consideration of resistor values to ensure stable operation of the integrated circuit. The choice of a 10k resistor and the subsequent addition of a 500k potentiometer provide a wide range of pitch adjustments, enhancing the overall functionality of the device. The use of heat-shrink tubing around the resistor serves to improve durability and prevent mechanical failure.

The inclusion of touch points for pitch adjustments adds an interactive element to the circuit, allowing for real-time manipulation of sound. However, the noted glitching indicates a need for careful design consideration to prevent unintended behavior during operation. The integration of an output jack with a resistor is essential for impedance matching and signal integrity, ensuring that the output can be effectively interfaced with other audio equipment.

Overall, the modifications and additions to the circuit demonstrate a thoughtful approach to enhancing its capabilities while maintaining stability and usability in a compact form factor. The use of second-hand components also reflects an environmentally conscious approach to electronics design, promoting reuse and sustainability in circuit development.Some of the components for the EQ are mounted on the pots. The only additions I`ve made to the circuit from the last posted schematic is to add a feedback loop from the line output to the switched side of the first input jack, so that the connection is cut when something else is plugged in. This feedback loop allows it to act as a sound source in its own right, even without any inputs. Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled in your browser. Although I hadn`t planned on doing so at first, I`ve decided to add the MC4024 VCO to Loid. I used the extra space on the board to add a 4015 shift registe r pair as well. The 4015 is yet another wires-straight-to-pins build. Found this thing at a second-hand store cheap- since it`s made out of clear(ish) plastic, I could see a couple of resistors on the circuit board, and thought it would be worth checking out for the price, in case one of them was a pitch control. Score! It was. Below is a shot (kinda blurry, sorry) of the circuit before bending. The resistor marked R2 ³ is the pitch resistor. You can also see the backside of the built-in speaker: The rest of the circuit wasn`t very exciting, the sound-making part was a blob-type IC.

The other possible bend would have been to add external play triggering, but retriggering while it was already playing didn`t interrupt what was already playing, so that wasn`t super-exciting either. What I ended up doing was taking out the existing resistor, replacing it with a 10k (it was 55k), and adding a 500k pot inline.

Here`s a shot of the board after modification, notice the heat-shrink tubing around the resistor for added strength: I ended up having to add a second 10k resistor to the opposite side of the pot, as 10k wasn`t enough resistance to keep the chip from crashing (easily fixed by cycling the power). Of course, a 20k resistor at the board would have worked too, but I`m fresh out anyway. I also added touch points (using screws) for changing the pitch- they also cause some glitching under certain circumstances, sometimes leading to crashes, which again can be easily remedied by cycling the power.

I also added an output jack (with a 1k resistor on the board end of the wire)- I had to go with 1/8 inch, due to size restrictions imposed by the enclosure. I also had to grind away some plastic which was getting in the way of the jack. Audio clip: Adobe Flash Player (version 9 or above) is required to play this audio clip. Download the latest version here. You also need to have JavaScript enabled Adobe Flash Player (s, it didn`t matter- but using it as an audio-f machine resides here ted to have JavaScript