Featured Engineer

Interview with Mickey Delp

Mickey Delp

Mickey Delp - Founder, Delptronics

How and when did you get into electronics?

My interest in building things goes back to early childhood. I was always taking things apart to see how they worked, and that has never changed. I think I took apart every toy I ever owned. My family were very supportive. They recognized it as inquisitiveness and not destructiveness. One of my fondest childhood memories is of my grandmother teaching me how to solder when I was seven years old. She had worked in a radio factory during WWII, sort of a Rosie the riveter. That skill has served me well for many years.

I had a book called “Magnets, Bulbs and Batteries” which taught me the fundamentals of electricity. I build a lot of gizmos with that knowledge. I distinctly remember wanting to build something that made sound, but just not having the skills at the time. My mother bought me an electric bell, like the kind that used to be in telephones, and that just thrilled me.

In 1977, my parents gave me the RadioShack 150-in-One Electronic Project Kit. This was my first introduction to electronics, as opposed to the simpler electrical circuits that I had been making. I spent countless hours building the circuits in the instruction book, and eventually began to design my own circuits. I remember the flash of insight when it occurred to me that the relay could be used to make a buzzer using the concept of the electric bell. In middle school I won the science fair three years in a row with electronic projects, all of which made some sort of sound.

Did you study electronics in college?

No, I studied computers. I had intended to go into robotics as a career, which seemed like a perfect fit for my interests. When I was about 12, I read in Popular Electronics magazine that Drexel University had just started a robotics degree program and decided that was where I was going. I did, in fact, go to Drexel, but not for robotics. In high school, I discovered computers, and my career went in that direction. I felt the same thrill in building a program as I did in building a circuit or a robot, but I think what pulled me in the direction of programming was the instant gratification that comes from simply typing in a program and running it. There were still a lot of little parts connected together, but they were all virtual. I also think I found it easier to debug a program than a circuit. Over the next 20 years, I had brief periods of time when I would dip back into electronics as a hobby.

How did you turn back to electronics as a career?

About three years ago, I started getting back into electronics in earnest. I bought a couple of kits to sharpen up my soldering skills, including some synthesizer kits. I learned Arduino programming. I dusted off a PIC microcontroller project board that I had bought a few years before and made some cool things with that. I got back into building electronic musical instruments, which was what I always loved to do. Analog sound synthesis fascinates me and I am focused on that now. I created a blog to share my experiences and started selling kits of some of my creations. I have now formed a company, Delptronics as the commercial outlet for my electronics work. So, now I have two careers: one in computers and one in electronics, but it is my goal to transition to electronics full-time.

Can you tell us more about analog sound synthesis circuits?

Every sound, such as the sound made by a musical instrument, has a distinct waveform. Modern digital synthesizers contain digitized versions of those wave forms to reproduce musical instrument sounds. This is called wave table synthesis. Early digital synthesizers used a technique called additive synthesis to combine multiple sine waves into various waveforms. Analog synthesizers primarily use subtractive synthesis techniques. Subtractive synthesis starts with simple oscillators to create very basic waveforms, such as square, sawtooth, triangle and, less often, sine waves. Then, filters are used to subtract certain harmonics of the basic waves. The most common filter is the low pass filter, but high pass, band pass and notch filters are also used. These filters would be familiar to any electrical engineer.

In addition to filtering, there are other techniques used to change the timbre of a sound. Frequency modulation uses one audio frequency wave form to change the shape of another wave form. Low frequency oscillators (LFOs) oscillate at sub-audio frequencies and add vibrato when used to modulate pitch or tremolo when used to modulate volume. Envelope generators create rising and falling voltages, the most common use of which is to control the rising and falling volume of note when a key is pressed and released.

The heart of any synthesizer is the voltage controlled oscillator or VCO. Typically, a keyboard will supply a voltage that represents to a note, and the VCO will oscillate at the corresponding frequency. However, all of the basic modules of a synthesizer, oscillators, filters and modulators, are voltage controlled. This universal voltage control means that any module can affect any other module. For instance an LFO can be used to modulate the cutoff frequency of a filter, or an envelope generator can control, not just the volume of a note, but the pitch, or the filter resonance. Infinite combinations can be created for infinite sound possibilities. This is what makes building analog synthesizers and individual synthesizer modules so interesting.

It may all seem hopelessly “retro,” but if you wait long enough, what was old is new again. I was just re-reading an article in an old issue of “Electronotes” from the 70’s that discussed VCO circuits. The author mentioned that with all of the new VCO chips available, there was not much need to build discrete oscillator circuits anymore. Well, those chips are now long out of production, and there is again a need for discrete circuits. Electronic music synthesis has had a very interesting history.

Can you elaborate on that history?

In the late 60’s and 70’s, the early days of synthesizers, pioneers like Bob Moog, Don Buchla and Alan R. Pearlman were creating instruments with the best technology at their disposal which was, of course, all analog. In the 80’s computers became more readily available and more powerful. Synthesizer makers again used the best available technology, and so music synthesis became all digital. In the late 90’s there was a resurgence of interest in analog synthesizers. They simply sound different than all-digital circuits. Today, synthesizers are an amalgam of analog and digital circuitry. Some of the most popular synthesizers used by musicians today are virtual synthesizers that use software modeling of the old subtractive synthesis techniques. New hardware like the iPad has put very powerful synthesizers in the palm of your hand, often with unique control mechanisms that go far beyond the keyboard. I think that right now is the most interesting time to be involved with electronic music synthesis.

In your blog, you talk a lot about circuit bending. Can you tell us more about that?

Circuit bending is the art of modifying an electronic device to make it produce sounds. Most commonly, the device was designed to make some sound, but the circuit, and hence the sound, is bent into something new and unusual that the designer never intended. My first experiment with circuit bending came at the age of ten. I had taken apart my toy cassette player, which was not unusual because, as I mentioned, I did that with all my toys. While I was examining the circuit board, I touched some of the metal parts and discovered that it made strange noises. It was a wonderful discovery and led to a lifelong interest in circuit bending and making strange electronic noises in general. My experiences parallel those of Reed Ghazala, circuit bending pioneer and the coiner of the term.

My circuit bending projects are a little more complex than most. Instead of just adding a few pots to change the sound, I tend to add additional circuitry including microcontrollers to really extend the musicality of the circuit. In fact, the first product I built for Delptronics, was the Bender Sequencer, which is a device that can make any sound circuit play rhythms and melodies.

Circuit bending is sometimes dismissed as being not “real” electronics, to say nothing of its reputation as being not “real” music! However, I think it is great segue to more complex electronics projects. It is all part of the burgeoning DIY trend that, I believe, is creating more electrical engineers.

So, you see future EEs coming from the DIY community?

Absolutely. It used to be that DIY electronics was something that engineers did in their spare time. Now, there is a huge DIY community. I would point to publications like “Make Magazine” and their Maker Faire events, local hackerspaces, the Arduino and Monome open-source hardware movements, the hundreds of kits available and of course thousands of websites – including EEWeb. Even Radio Shack is getting back to their DIY roots by beefing up their parts department and publishing a new DIY newsletter (I was featured in the first issue). Compared to when I started, there are now tons of resources for learning electronics, and the tools available to individuals are very sophisticated. There are even free PCB design tools and inexpensive board houses that handle low volume at very reasonable prices. So, yes, I foresee a lot of people who start out with DIY electronics choosing electrical engineering as a career.

What are you working on right now?

I have several interesting projects in development now. They all involve electronic music. Most of them combine analog sound synthesis circuits with microcontrollers. The most interesting and challenging project involves using capacitive touch to create new music control interfaces. I am also going to be producing some new kits for the DIY synth community. I always want to keep that as part of my business.

What do you like most about what you do?

Teaching. I conduct a monthly workshop at the local synthesizer shop to teach people about electronics. It is a big thrill to see the look on people’s faces when they plug in something they just build and it works. I love to share my passion for electronics and electronic music. That is really rewarding. When I was a kid, whenever someone asked what I wanted to be when I grew up, I would say I wanted to be an inventor. Last week, my sister told me that she asked her six year old son what he wanted to be he said “I want to be an inventor, just like Uncle Mickey.”

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