I’ve always wanted to know what the “tube magic” was all about. There is much opinion in the science of music production, probably because music and its perception is highly personal and subjective. Ive always imagined that since transistor amplifiers were “perfect” with their large amounts of negative feedback, great linearity, and low THD that tube amplifiers must add something to sound that generates their appeal. From the reading I’ve done it has to do with harmonics.
Shawon Shahryiar over at Embedded Lab shared a how-to on making a SPL dB meter:
Sound needs a medium for propagation or travel. It can’t travel in vacuum. Normally air is that medium but sound can also propagate in liquids and other states of matter. I am not going to lecture on how sound travels and its properties as Wikipedia details everything well here. Everything we see around us has a measurement and a unit. In case of sound pressure, the unit is decibel. Our basic requirement is to be able to measure Sound Pressure Level (SPL) in decibel scale with a typical 8-bit microcontroller, an ordinary microphone and without involving complex algorithms.
Measurement of sound has a number of uses. For instance, monitoring sound pollution, security system, monitoring the quality of an amplifier, detecting sound profile of an environment, etc.
Here, I will show how you can make your own version of the 555 timer using just NAND gates, opamps , a transistor and a few resistors! Now, you may think what is the purpose of building this when you can buy the IC at very cheap rates. The answer is, you learn electronics better, understand how the actual IC functions and improve your confidence in building electronic circuits.
Adam Zeloof made his own guitar pedal based on the Zvex Fuzz Factory:
The Z.VEX Fuzz Factory is an amazing little fuzz pedal designed by musical and electrical wizard Zachary Vex. I was introduced to it through Matt Bellamy‘s unique guitar style, and fell in love with its out-of-this-world sound. While I was tempted to buy a Z.VEX original for their beautiful hand-painted cases, I decided to save a few bucks and make my own.
In this new project I am again using PIC16F628A microcontroller. The goal is simple digital clock with 7-segment LED display and the clock will have no additional functionality – no alarm, no seconds digits, no date. The latter can be added in the software though. For the RTC chip I chose DS1307. For the LED display I used Kingbright CC56-21SRWA.
The input is at 50Hz and the output is at 60Hz. So for every 5 input cycles, we want to generate 6 output cycles. We will be synthesizing a sine wave in software, and there’s no reason not to go with a conventional lookup table of 256 bytes. The PWM will be averaged out by the coils in the motor. It may even be possible to drive it with a square wave, but there is a self-starting mechanism I don’t want to interfere with. A synchronous single-phase motor normally will spin in either direction, and if you want it to spin only one way (as is the case with a clock) extra components are needed. It could be a mechanical pawl that stops it starting in the wrong direction, but the rotor spins very freely in either direction when the clock is powered off. More likely, there is a capacitor and/or additional coils which provide the shove in the right direction.
This is a battery-powered EV charger that allows destination charging where L2 charging is not ordinarily available. This can be used as a range extender for electric vehicles with smaller batteries. This system has a ~7kWh battery which should charge my Cadillac ELR to more than 60%. This has been a fun project with plenty of lessons learned.
Ryan Flowers writes, “A fun project for every QRP enthusiast is an L-match tuner. We’ve built a couple here at MiscDotGeek and our latest build inspired Billy Dunn (AF5HD) to build a similar tuner. We have to say, this one turned out better than ours did!”
The 1750Hz tone bursts are often used to trigger repeaters. There are several methods to build 1750Hz tone generators which including TC5082 divider, using MCUs, etc.
In this post, I present another 1750Hz tone generator which I built using 74HC4060 high-speed 14-stage binary ripple counter and 7.168MHz crystal. In this design, 74HC4060 is used to drive the crystal and divide its output by 4096. By using 7.168MHz crystal, this circuit produces 1750.0Hz square wave output with a 50% duty cycle.