Member Profile: Jack Philpot

Jack Philpot

Jack Philpot

Member Name: Jack Philpot

Location: South Holland, IL

Occupation: Jack is retired from AT&T. At one time, he was a frequent contributor to Audio Amateur. Jack’s articles appeared in several Audio Amateur issues including February 1978, February 1979, February 1980, January 1983, February 1983, April 1983, February 1986, February 1988, April 1989. He also wrote an article for Speaker Builder that ran in January 1982.

Member Status: Jack said he started subscribing to audioXpress when he discovered that it was a continuation of the Audio Amateur publication. He said he was hoping to find back issues that may contain an upgrade article on the Adcom GFP-565 preamplifier.

Audio Interests: Jack is very interested in home audio, both new and vintage.

Most Recent Purchase: He recently added a Cambridge DAC for for listening to high-resolution digital music sources and an Ortofon 2M Blue, designed for high-performance reproduction of analog records, to his home audio system.


Adcom GFA-535 II power amplifier

Current Audio Projects: Jack converted two dual-mono Adcom GFA-535 II power amplifiers to mono blocks with dual-power supplies. He used an extra pair of outputs from spare modules and added them to each driver board similar to the GFA-545 II. He built the unit so that the output terminals are bridged for bi-wiring.

Q&A: Engineer Takes a Chance on Start-Up Audio Venture

SHANNON BECKER: Tell us about your company Tortuga Audio. Can you also share the story behind your sea turtle mascot?

Morten Sissener used his engineering knowledge to open his own audio design boutique, which he named Tortuga Audio.

Morten Sissener used his engineering knowledge to open his own audio design boutique, which he named Tortuga Audio.

MORTEN SISSENER: Tortuga Audio is a boutique audio design, manufacturing, and marketing company located in South Florida. At present we only sell through the Internet via our website although we expect to add channel partners in the future probably starting in Europe.  We’re a little over a year old in terms of coming out with our first products—a line of passive preamplifiers built around light-dependent resistors (LDRs). We actually manufacture here in the US. While it may not hold much sway with customers, there’s something satisfying in being able to say “Made in the USA.” That’s the short and mostly dry of it.

Our mascot is the sea turtle wearing a set of headphones. People who know me wouldn’t describe me as being particularly religious or spiritual, but I’ve come to accept the sea turtle as my totem. A totem is an object or symbol representing an animal or plant that serves as an emblem of an individual, family, or tribe. You don’t pick your totem. Your totem picks you.

I’ve always had a fascination with a place called The Dry Tortugas. It’s a small cluster of islands about 70 miles west of Key West, FL. I first heard of this place in an adventure book I read when I was a young boy. I fell in love with reading, warm blue water, and The Dry Tortugas.

Years later, I bought a boat in South Florida. The first time I took that boat offshore I went out 20 miles, stopped, and turned off the engines. I was out of sight of land. The water was glassy calm. Thirty feet off the starboard beam a sea turtle surfaced and stared at me. I stared back. This lasted for over a minute. Then the turtle dove away. The name I’d already put across the transom of my boat was The “Tortuga Dreamer.” So when it came time to name my audio company you could say it named itself—Tortuga Audio.

SHANNON: What prompted you to start a company that designs and manufactures audio equipment, particularly in 2010 when the economy was so uncertain?

MORTEN: Starting an audio company that caters to a shrinking niche of audio fanatics as the masses continued shifting to low-resolution MP3 audio and inexpensive ear buds was arguably a questionable business decision. However, it was definitely a passionate business decision. Approaching 60, I figured it was time to pursue my passion rather than my resume. And I’ve always been passionate about technology, audio, and music. You could say the rational engineer decided to follow his heart.

SHANNON: What kind of audio products do you build? Can you share some of your design challenges?

As with all Tortuga Audio’s LDR passive preamplifier (LDRx) products, the LDR6 has unity gain passive (no active amplification) volume controllers that employ digitally controlled audio grade light-dependent analog resistors to provide neutral and transparent attenuation.

As with all Tortuga Audio’s LDR passive preamplifier (LDRx) products, the LDR6 has unity gain passive (no active amplification) volume controllers that employ digitally controlled audio grade light-dependent analog resistors to provide neutral and transparent attenuation.

MORTEN: While the business rationale behind the founding of Tortuga Audio may not win first prize in any business plan contest, the decision to pursue our flagship product was, and remains, highly rational and compelling.

Back in 2009, I was building a tube preamplifier mostly as an exercise to see if tubes could really offer more than solid state. I was less than impressed with the results even though I’d used a well recognized kit/design and top-of-the-line components.

At the time I was using a motorized Alps Blue Velvet potentiometer for volume control. Thinking that perhaps I could improve the sound by going to a stepped attenuator, I stumbled across LDRs. I cobbled together a very basic LDR volume control based on bits and snippets of information on the Internet, pulled out the Alps potentiometer and installed the LDR. The result was nothing less than a revelation!

The fact that this tube preamplifier went from disappointing to awesome simply by changing the attenuator made quite an impression on me and frankly I couldn’t stop thinking about it. It’s what engineers do. Especially this engineer. I can’t stop thinking of ways to do things differently or better. I’ve always hated that old saying, “if it ain’t broke, don’t fix it.” Can you imagine Steve Jobs saying that?

This led me to ask a simple question. Why do I need a preamplifier? Why preamplify and then amplify? Do I really need the additional gain? In most instances, the answer is no.

I looked at all the complexity of that tube preamplifier and decided to pull out the LDR attenuator, set the preamplifier aside, and use the LDR as a purely passive volume controller. The result? It sounded even better without the tube preamplifier. And not just a little bit better, a lot better! I was so impressed with this LDR attenuator that I couldn’t leave it alone. From that point forward, I dove into the deep end of LDR volume control.

SHANNON: What makes your audio equipment unique?

MORTEN: LDRs are challenging to work with because  they are both nonlinear and variable. Nonlinear means their relationship between control signal applied to an LDR and the resulting resistance level is not a simple fixed ratio. Variable means that this nonlinear relationship can vary from one LDR to the next even with LDRs of the same model, from the same manufacturer, and from the same production run. That’s a lot of variable nonlinear stuff and that makes it very hard to get consistent predictable behavior when using LDRs for volume control. No designer likes to work with audio components that behave like LDRs.

Part of our solution to taming the wild LDR was to design a programmable digital control unit that enables us to control the analog LDR with proprietary software algorithms. We combine digital control with a two-step testing protocol such that each LDR preamplifier we build has a custom set of software-based correction curves that ensures  predictable performance. This is neither simple nor easy, but we’ve put an enormous amount of time and effort into developing the software and hardware tools to do this cost effectively.

The result is a unique and game-changing LDR-based passive preamplifier (volume control) design that we believe rivals not only all other passive preamplifiers out there but also meets or beats even the best high-end active preamplifiers. While I happen to believe this personally, feedback from our customers and reviewers continues to reinforce this view.

SHANNON: Are you currently planning or working on any new product designs?

The Tortuga LDR3x is a preamplifier controller board designed around LDRs that enables DIYers to build a passive or active preamplifier including remote control.

The Tortuga LDR3x is a preamplifier controller board designed around LDRs that enables DIYers to build a passive or active preamplifier including remote control.

MORTEN: Our core focus continues to be advancing the development of our LDR-based volume controller products. In the third quarter of 2012, we came out with our LDR1 and  LDR6 passive preamplifiers, which are finished preamplifier products. In the third quarter of 2013, we introduced the LDR3x passive preamplifier controller board (the LDR3x), which we marketed to the DIY audio community. We plan on continuing to serve the high-end audiophile consumers with finished products and provide DIY products to audio enthusiasts who’d rather build it themselves.

In November of 2013, we introduced the HiZ upgrade to our LDR-based preamplifiers. The HiZ algorithm enabled us to raise the input impedance of our LDRx products resulting in a remarkable improvement to an already fantastic-sounding preamplifier/volume controller. As far as we know, nobody else has done anything like this.

In terms of what’s next, we are working hard on coming out with our new line of LDRx passive preamplifiers including our new LDR3B, which I believe may be the first-ever LDR-based preamplifier for balanced audio. We hope to release the LDR3B before the end of March. Since we are a relatively low-volume business and want to offer distinctive products that are not priced out of reach to most audiophiles, we’ve decided to manufacture our own enclosures in-house going forward. This will keep our costs down while enabling us to offer high-quality products and still retain the flexibility of small-batch production, quick design changes, and the ability to offer custom solutions.

Beyond our next generation line of LDR preamplifiers, we plan to introduce a buffer companion product to our passive preamplifiers that will expand the application of our preamplifier/volume controller to include sources and amplifiers where a pure passive may not be the best fit. We are also considering the introduction of an integrated amplifier product that will allow us to target a broader market. These will be second half of 2014 products.

Longer term, we are quite excited about the prospects for an OEM version of our LDR preamplifier controller product. Every active preamplifier or integrated amplifier sold and marketed to the audiophile community that currently uses a potentiometer for volume control would sound better with a Tortuga Audio LDR volume controller. And along with being the best-sounding attenuator available, it also includes input switching, IR remote control, and a built-in encoder control.

SHANNON: How did you become interested in audio electronics?

This 3-D CAD rendering shows the front (a) and the back (b) view of a prototype enclosure design for Tortuga’s new LDR3B balanced passive preamplifier, a new product line that will be coming out in March.

This 3-D CAD rendering shows the front (a) and the back (b) view of a prototype enclosure design for Tortuga’s new LDR3B balanced passive preamplifier, a new product line that will be coming out in March.

MORTEN: As a newly minted mechanical engineer, I started my professional career in the aerospace sector working with complex electromechanical systems. This segued into energy when the company I was with in California became interested in alternative methods of power production. This eventually led me into industrial construction, large capital project development, project finance, software, sales and marketing, wind, solar and biofuels, as well as several start-ups along the way. An interesting ride but all along I was remained very interested in technology, software development, audio, and music. I decided it was time for my true interests to rule the day rather than the inertia of my resume. Plus I’m just an unapologetic techno-geek with a big creative itch that needed scratching. I also like to run my own show.

SHANNON: Where do you see the audio industry in 10 years?

MORTEN: I believe the high-end audiophile market with many components costing $10,00 or more is going to continue to decline into obscurity. Many have argued that the high-end market may already be in a terminal death spiral of rising prices and shrinking volume. I tend to agree. If true, that’s not a sustainable scenario for high-end audio.

The audio listening paradigm of a big-rig stereo in the living room that the aging baby boomer audiophiles were introduced to in the 1970s is not the central paradigm of contemporary audio. Where only a few years ago you could go into a big box store and see racks of receivers, rows of speakers and even a “high end” listening room, today, most of that is simply gone.

Ironically, we are collectively listening to more music from more sources more of the time than ever before. Access to music is wide if not deep. The Internet has become the new radio. Online streaming is becoming the norm for most consumers while buying and owning music is slowly retreating, This is especially true for physical media such as CDs.

Despite this bounty of access, we’ve also experienced the concurrent dumbing down of audio quality (e.g., low-resolution MP3 files) and listening through lo-fi hardware, most of which has gone mobile. So it’s an interesting mixed bag of good and bad news for us audio nutters.

While the road ahead may be unclear, I believe that a significant percentage of all those 20-to-30-something Millenials and Xers are eventually going to raise the bar on their audio game as they grow older and their incomes rise. But you can forget living rooms filled with big, heavy, and expensive gear as the norm. “Personal audio” will continue to grow and evolve and that means computer centric audio.

For most, that will mean DAC->preamplifier (volume controller)->amplifier->speaker configuration in which the DAC/preamplifier/amplifier separates will trend toward being a single integrated component. Speakers will be smaller, but higher quality near-field units usually located on desks or bookshelves near where people sit and work with their computers. And yes, no doubt a subset of these folks will eventually go with some bigger gear as well. But I believe we’re talking a few thousand dollars of audio gear and not tens of thousands of dollars.

SHANNON: Do you have any advice for audioXpress readers who want to build their own sound systems?

MORTEN: I tend to be a minimalist and a skeptic and try to not get distracted by bright shiny objects.  What I recommend is forget cables, power conditioners, cryogenics, and ceramic outlet face plates. Focus first on what matters the most.

Nothing will affect your audio enjoyment as much as speakers. Poor-quality speakers can make a great rig sound awful. Great speakers can make a low-quality rig sound remarkably good but not great. My personal favorite these days are full-range speakers with alnico magnets. Full-range speakers are point sources with no crossovers or phase-shifting. They offer amazing clarity, articulation, and bass.

Second (self-serving statement alert!) get the best preamplifier/volume control you can. Every note gets squeezed through the bottleneck of your volume control and this is where the most irreparable harm happens to your audio signal, even if everything else you have is really good.

Third, choose the best DAC you can. DACs are evolving rapidly, which is fantastic news.

The last thing I would worry about in terms of main components is your amplifier. Not that amplifiers don’t matter, they just don’t matter that much compared to everything else. And the good news is there’s a huge selection of great amplifiers out there.

To summarize, if you’re deciding on how to prioritize your money, make it speaker->preamplifier (volume control)->DAC->amplifier. Of course, if you’re into vinyl then a good turntable and cartridge is critical, but don’t forget the phono preamplifier. This can get expensive fast. I’d expect to spend a few thousand dollars to get into the land of great vinyl audio. It will cost more for fantastic.

Once you’ve got a decent system you really enjoy listening to, you can begin the madness of tweaking this and that, trying various cables, power conditioners, and so forth. But remember that the purveyors of audio equipment will tell and sell you practically anything you can imagine to get that extra ounce of goodness out of your rig.

Despite all the changes happening in technology and the audio industry, music remains a wonderful art form and audio is still a great hobby. Enjoy!

Member Profile: Doug Pomeroy

Doug Pomeroy

Doug Pomeroy

Member Name: Doug Pomeroy

Location: Brooklyn, NY

Education: Doug has a BA in Psychology from the University of California, Los Angeles (UCLA).

Occupation: Doug is an audio engineer. Among his career highlights, he was a Columbia Records staff recording engineer from 1969-1976.

Member Status: Doug said he has been reading audioXpress magazine since its first issue.

Affiliations: He is very active in the professional audio industry. Doug is a member of the Audio Engineering Society (AES), the Boston Audio Society, and the Association for Recorded Sound Collections (ARSC).

Audio Interests: Doug said he enjoys audio restoration and audiophile recording.

Most Recent Purchase: His most recent purchase is WaveLab7, which is used for mastering, audio editing, and restoration. Doug said he tried it and does not like it.

Current Audio Projects: Doug is working on a project that involves the transfer and restoration of Count Basie “acetates.“ William James “Count” Basie (August 21, 1904–April 26, 1984) was an American jazz pianist, organist, bandleader, and composer.

Dream System: In response to this question, Doug said “I have no more dreams, but I might like some good ribbon mics.”

Q&A: Ken Heng Gin Loo – DIY Audio Appeals to Applications Engineer

Ken Heng Gin Loo

Ken created the website because of his interest in DIY audio, in particular tube amplifiers, Class-T amplifiers, NOS DAC, high-efficiency loudspeakers, and high-quality audio reproduction.

SHANNON BECKER: Tell us about your background and where you live.

KEN HENG GIN LOO: I’m a Malaysian Chinese. I spent a wonderful childhood in a small and peaceful town called Taiping, Perak, up North in Peninsular Malaysia.
I’m fortunate that my father could afford to send me overseas to the United Kingdom to pursue a bachelor’s degree after locally earning my diploma in Electrical and Electronics. Now, I’m a graduate in Electrical and Electronics Engineering (Honors) from the University of Manchester, UK.

I currently live on a beautiful tropical island named Pulau Pinang (aka Penang) in Malaysia. It is an urbanized and industrialized state that houses several the multinational corporations (e.g., Intel, Agilent, Motorola, Altera, National Instruments, etc.). Yet, it retains its historical heritage and it is one of the UNESCO World Heritage sites. Downtown is filled with historical sites, excellent local delicacies and seafood, and many beachside resorts.

I live in a terrace house with my lovely wife Brenda and 3-month-old baby girl Ember. In the past, I worked as an engineer for several multinational corporations. Now I work at Intel (for more than eight years) as an applications engineer. I focus on customer-enabling team program management, working with high-speed electronics applied in tablets, notebooks, and PCs.

SHANNON: How did you become interested in audio electronics?

KEN: I was “trained” in hi-fi very early, way back in my primary school years. I’m fortunate to have a hi-fi enthusiast as a father. He plays vinyl, and previously used cassettes before moving to CDs in the 1990s. I was brought up (or spoiled?) with high-quality stereos since I was a youngster.

I started to like tube equipment when I heard the combination of a Unison Research Simply 2 and a B&W 601S2 speaker in a shop in Hsinchu, Taiwan. I seriously started to create DIY audio projects when
I was working in Taiwan in early 2000. A friend, who was also a tube dealer, introduced me to his DIY 300B tube amplifier that was driving a pair of vintage Tannoy 15” dual-concentric speakers. It was the Tannoy GFR, if memory serves me right. The sound they produced was made in heaven and no setup that I’d encountered at that time was close to producing what I heard that day.

I was hooked on the glowing tubes. I started reading about vacuum tubes online, in books, and in magazines (e.g., Sound Practices, Audio Amateur, audioXpress, etc.). I wanted to learn more about vacuum tubes so that I could build a sound system of my own. I also started “wasting” money collecting NOS tubes for my future projects. Now, I have more tubes than I will ever need in my entire lifetime. Maybe if my daughter inherits my interest in audio technology, she will find a use for them. Who knows?

Among his many projects, Ken built a 2A3 amplifier. However, instead of a 2A3 tube, he used the double plate NOS 6B4G because it has the same electrical characteristics as a 2A3 tube. The main difference is that the filament uses 6.3 instead of 2.5 V.

Among his many projects, Ken built a 2A3 amplifier. However, instead of a 2A3 tube, he used the double plate NOS 6B4G because it has the same electrical characteristics as a 2A3 tube. The main difference is that the filament uses 6.3 instead of 2.5 V.

SHANNON: Describe your first personal project. Why did you build it? Is it still in use?

KEN: Tube amplifiers were still uncommon in those days and purchasing one was costly. It was definitely out of my budget when I was a young engineer. Back then, an ordinary tube amplifier alone was two or three times my monthly pay. Since I have knowledge in electrical engineering and electronics (well, sort of, since I studied all solid-state electronics), I thought I would attempt to build a tube amplifier. I thought making a tube amplifier from scratch certainly would not be difficult for me. So, I started building tube amplifiers because the DIY methods made them accessible to me.

A Taiwanese friend assisted me with my first build. He did most of the design work and I did all the soldering since I was still very new to DIY tube amplifier construction. It was a two-stage all triode amplifier with a 300-B direct heat triode driven by a 5842 miniature triode. The sound was sweet and warm even though it was (un?)matched with a small B&W 601S2 bookshelf speaker. (I still have this pair of speakers today!) They are definitely 10 times (exaggerated!) better than all the entry solid states I owned or bought when I was in the UK.

My true first 100% built-by-myself project was an all Russian Reflektor 6C45PI with a 6C33CB triode mono-block tube amplifier. I read an article about a 15-W SE 6C33C-B amplifier that Erno Borbely published in Glass Audio magazine. His article sparked the idea for my own project. I used his design to build my own 6C33C-B amplifier circuit.

“I’m a mischievous youngster! I’m an engineer! I can do much better than him!” So I thought. Well, it didn’t go that well.

SHANNON: What kinds of audio projects do you build? Can you share some of the challenges involved with the designs?

KEN: I build speakers, pre- and power amplifiers, DACs, subwoofers, mains filters, and almost any kind of audio-related gadget. Some of the projects I have built over the years include: Class-D amplifiers with Philips and Tripath integrated circuits, Gain Clone clones (LM3886 and LM1875), Fostex FE167E bass reflex bookshelf speakers out of real wood, a Fostex FE167E in TQWT enclosure, an Altec 640D in Altec 620D cabinet, several 300B SE amplifier variations, 45 SE amplifiers, 6B4G amplifiers, an 1H4G preamplifier, a 6SN7 preamplifier, a 5687 preamplifier, a 6C45PI SPUD, a 5842 SPUD, an EL34 single-ended amplifier, a Tannoy HPD385A active crossover, and many more that I can no longer remember.

I still have some of the completed projects. I’ve also posted a few of them on my website ( DIY audio is challenging in many aspects, especially if you want your designs to sound really good and be reliable. To get something to work is easy. To master it is rather difficult.

Ken used this chassis for a hybrid amplifier design. The front plate and heatsinks are made of aluminum. All the holes are pre-drilled and the chassis accessories are supplied as a package.

Ken used this chassis for a hybrid amplifier design. The front plate and heatsinks are made of aluminum. All the holes are pre-drilled and the chassis accessories are supplied as a package.

Some of the most challenging areas include:

  • Aesthetics—I admit this is one of the challenges I always face. I do see that there are a lot of DIY designs online that look fantastic, almost as good as commercial designs. But for the projects to look good, you need to spend significant time, effort, and money from the design’s start until the end. However, my bias would lean more toward sound than looks. For my projects, I definitely spend more time on the design and the components rather than the finished look.
  • Test and Measurement—This is something I find really challenging on financial and knowledge terms. My daily job includes testing and measuring computer motherboards for power, signal integrity, compliance, eye diagram, and so forth. I use a lot of test and measurement equipment (e.g., multimeters, LCR meters, oscilloscopes, spectrum analyzers, and various other meters). This equipment is expensive and not something an ordinary DIY guy can afford to purchase for personal use. An oscilloscope can cost more than a house in Penang.
  • Measurement Methodology—This is a topic on its own. A different methodology or setup yields different results and that is sometimes misused because end users occasionally deviate from the figures/specifications that matters the most. Audio design is an art. Or perhaps it is better to say audio design is a black art? When I was a young graduate, I thought that if I got the circuit right, good sound would follow. It is not that easy! Everything matters, from component selection to the layout.
    I’m often amazed that some people think tidy wiring equals good sound. This will not guarantee good sound, but it does help future troubleshooting.
  • Separating Truth from Fiction—One thing I personally do not like is trying to differentiate among the hype or claims with hidden/personal agendas. I was, and sometimes I still am, tricked into buying something (DIY parts/components) that does not perform as claimed. There are many out there. So, beware!
  • Last but not least, the biggest challenge for all DIY audio hobbyists is that DIY audio projects often involve carpentry and electrical/electronic, which can sometimes be dangerous. You must work with sharp objects, live electrical connections, and tools. Take precautions and be safe.
Siegfried (Sigi) Maiwald of Wuppertal, Germany, shared his multi-cellular horn project on Ken’s DIY website.

Siegfried (Sigi) Maiwald of Wuppertal, Germany, shared his multi-cellular horn project on Ken’s DIY website.

SHANNON: What has been the most creative project you’ve received on your website?

KEN: I received these two amazing DIY speaker and DIY tube amplifier projects from Siegfried (Sigi) Maiwald of Wuppertal, Germany. One day, I met Sigi via the website’s feedback form and we became good friends due to our DIY audio hobby.

Sigi’s approach to DIY audio, his attention to detail and workmanship, not to mention his energy (and strength to manage such a humongous speaker), and spirit are simply outstanding.
In terms of creativity, he used a broom as the support/stand for a multi-cellular horn! In addition, he used the “УO186” as an inexpensive substitute for the ultra-rare and ultra-expensive RE604, which is definitely cool. I would not have known you could do that. Too bad the project suffered at the end due to a mishap.

You can check out his projects (write-up and photos) at and at

The DIY 300B amplifier circuit design and components use a Tung-Sol 5687WA military tube as the pre-amplifier and driver stage. The power tube is JJ 300B and the power supply uses a RCA 5U4GB full wave rectifier tube.

The DIY 300B amplifier circuit design and components use a Tung-Sol 5687WA military tube as the pre-amplifier and driver stage. The power tube is JJ 300B and the power supply uses a RCA 5U4GB full wave rectifier tube.

SHANNON: With all the products that are available, why do you think audiophiles continue to experiment and build their own equipment?

KEN: DIY audio is one of those continuing trends. Fanned by the increasing price of audio equipment, it remains popular among the DIY-audiophiles. Everyone wants a piece of high-end equipment but the disproportionate price vs. performance and the return of investment places many high-end products out of reach for the general community.

Cost aside (DIY is not inexpensive either!), I’m sure DIY audiophiles will continue to design and build because of the satisfaction and enjoyment they receive when listening to their own creations and masterpieces! I am proud to say that I made most of my home audio gear!

The December 2013 Edition of audioXpress is Now Available Online

In this month’s issue, you can read our review of the elysia xfilter 500, an extraordinary equalizer “Made in Germany” in a 500-series format that offers a precise stereo image based on computer-selected, stepped potentiometers and low-tolerance film capacitors. In our Standards Review column, we address the new Audiobus and Apple’s Inter-App Audio technologies for iOS platforms. The T&M series offers the second part of the excellent “Designing for Ultra-Low THD+N” article by Bruce Hofer. Read more about reinventing low-frequency devices to fit compact sizes in the Mike Klasco and Steve Tatarunis series, “The Lowdown on Woofers, Subwoofers, and Bass Shakers.” And don’t forget our monthly Sound Control article series in which Richard Honeycutt discusses absorption and why it is considered “The Oldest Tool in the Modern Acoustician’s Toolbox.”

In this issue, Shannon Becker interviews Ken Heng Gin Loo and learns why DIY audio projects appeal to this applications engineer.

In our project-oriented section, you can read about The Cathedrals speaker system designed by Ken Bird and read our second serving on “Tips to Resurrect a Classic Speaker or Design a New System” by Thomas Perazella. Also, find out how to “Build a Sound Level Meter and Spectrum Analyzer” in another great project article by Ron Tipton.

Check it out at

Visit for information on how you can receive a monthly magazine copy wherever you go.

SSL Live Console Ships to Customers and Sales Partners

Solid State Logic (SSL) has been a dominant console designer and manufacturer for music, broadcast, and post production for more than 35 years. However, SSL had never produced a product specifically designed for live audio production, until now. SSL’s reputation and business was built on visionary operational design and benchmark-quality standards in audio reproduction and manufacturing so expectations were high.

SSLLiveFrankfurt The early response to the SSL Live from front of house (FOH) and monitor engineers has been extremely positive. The more operators who see it, the more the excitement surrounding the console grows. The console’s operational flexibility, sonic performance, and the sensation of “finger painting with audio” via the gestural touchscreen are among the highlights. The on-board effects and channel processing toolkit and the SSL Blacklight system, which simplifies running audio and control between console and stageboxes, delivers a surprising amount of power at a compelling price.

The first three consoles shipped to UK-based Britannia Row, a global tour production company, for use on Peter Gabriel’s European “Back to Front” tour. Another two shipped to SGroup in France. Console manufacturing production for 2013 has been sold out since July. Details of the new commercial partner network for SSL Live are available on the SSL website.

SSL’s CEO Antony David said, “The on-schedule completion of the new Live console is an important milestone for SSL. This has been one of the biggest developments we have undertaken for some time and marks the first application of our new Tempest digital platform. We have been very encouraged by the response from mix engineers, rental companies and our channel partners since we presented the console in April this year. Demand has substantially outstripped our initial production plans, but we will return to reasonable lead times by early 2014.”

SSL-UK-HQ-Staff-CelebrationSince April, SSL has expanded its Live product team with key hires that include Jason Kelly as Live Consoles Product Manager based in the UK office and Jay Easley as Vice President of Live Consoles to lead SSL’s live sector sales operation in North America. Certified training courses have also commenced, with a focus on commercial partners and initial purchasers. A training program for the wider operator community is scheduled to begin in January 2014.

The SSL Live will be exhibited at ISE in Amsterdam (the Netherlands) in February 2014 and at Prolight + Sound in Frankfurt (Germany) in March 2014. In June 2014, the company will also exhibit at InfoComm (Las Vegas, NV).

Solid State Logic

Q&A: Daniel Weiss – Audio Engineer Focuses on the “Masters”

Daniel Weiss founded Weiss Engineering in 1985. The company designs and manufactures digital audio equipment for mastering studios.

Daniel Weiss founded Weiss Engineering in 1985. The company designs and manufactures digital audio equipment for mastering studios.

SHANNON BECKER: Tell us a little about your background and where you live.

DANIEL WEISS: I live in Uster, a small city close to Zurich in Switzerland. In the 1970s and 1980s, I played music in a band, first as a violin player and later as the bass guitarist, which seemed preferable to the other band members. I also built various synthesizers, amplifiers, and speakers. I did a four-year apprenticeship as an electronics technician and during that time two friends and I formed a company called “White Amplifiers.” We built amplifiers and speakers for musicians in our spare time. After the apprenticeship, I studied electronics engineering and eventually graduated with a BSEE.

SHANNON: In 1979, you joined Studer-Revox as an electronics engineer working in the digital audio lab. Can you share details regarding your work on the sampling frequency converter design?

DANIEL: In 1979, Willi Studer decided to enter the digital audio era and established the “PCM laboratory” with almost all the lab members being newly recruited engineers and technicians. We were kind of an isolated group as the other labs were slightly suspicious of digital audio technology. We also had a hard time (at least it seemed to me) defining digital audio products that would make sense in a mainly analog world.

There were several digital audio recorders around at the beginning of the 1980s (e.g., Sony, 3M, Soundstream, JVC, Mitsubishi, etc.). There wasn’t much standardization back then so the sampling rates and interface formats greatly varied. Thus, it made sense to create a universal sampling rate converter with custom wired interfaces. This became the SFC16, and I did most of the hardware design. It was a 6HU/19” unit with digital filters built in so-called distributed arithmetic. It is a very clever architecture that avoids the need for DSP or multiplier chips. For most of the units sold—I think 30 of them were manufactured—I also did custom interfaces.

One of the largest setups of a 102 Series system was used at Sony Music in New York in the form of the IBIS digital mixing console.

One of the largest setups of a 102 Series system was used at Sony Music in New York in the form of the IBIS digital mixing console.

SHANNON: What other types of audio products did you design? Can you share some of the challenges involved with the design(s)?

DANIEL: My colleagues at the PCM lab pursued various other projects, such as A/D and D/A design, analog reconstruction filter design (I also was involved), research in de-noising, and a preview unit for the delay required in vinyl cutting. This resulted in a A/D and D/A 6HU box, with enough memory to do the delay. It was not a simple task back then.

As Studer was mainly a tape recorder company, the design of a digital tape recorder was inevitable. The first model was an eight-channel unit using the newly established Digital Audio Stationary Head (DASH) format, which enabled you to interchange tapes with ones recorded on other DASH recorders. I did the audio processing unit for that eight-channel recorder, which was required for interpolation in case the data read from the tape could not be reconstructed via the error correction scheme employed.

Those were interesting times at Studer, as we were pioneers in the pulse code modulation (PCM) audio field. We did many side projects, such as a digital sine generator for measuring purposes (Audio Precision did not exist back then) or a study on TIM measurements with a new approach or a PWM-based analog track on the digital tape and so forth.

SHANNON: In 1985 you founded your own company, Weiss Engineering ( Initially, your company focused solely on designing and manufacturing digital audio equipment for mastering studios. How and why did you select that specific market niche?

DANIEL: One day in 1984, when I still was at Studer, a customer came to our lab and asked for an interface between a Sony F1 portable digital audio recorder and a Sony 1610 digital audio recorder. The F1 did not have any digital I/O, so it had to be a custom made interface box. Studer does not do such custom work, so I made that interface for the customer in my spare time. The customer was Ben Bernfeld, a recording and mastering engineer from Harmonia Mundi Acustica in Germany. He knew exactly what was required in terms of equipment for CD mastering (or pre-mastering to be exact). So we decided to build a modular digital audio system to interface and process digital audio. I did the design and manufacturing while he organized the sales. CD pre-mastering was popular in the US mainly, so we concentrated on that market.

SHANNON: Tell us about Weiss’s first product. Is it still being sold today?

The potential of a Weiss Engineering Mastering Studio “Mastering Mansion Madrid” uses  Weiss Gambit Series equipment, which are the white faceplate units on the left.

The potential of a Weiss Engineering Mastering Studio “Mastering Mansion Madrid” uses Weiss Gambit Series equipment, which are the white faceplate units on the left.

DANIEL: The first system became the Harmonia Mundi Acustica BW-102 unit, starting with modules for F1, 1610 interfacing, a digital high-pass filter for DC offset elimination, a digital de-emphasis and a digital level control module.

Over the years, dozens of modules were added. We even did digital mixing consoles based on the BW-102. The largest one was a 32-channel console with four auxiliary buses. Another one was a 24-channel configuration with GML fader automation used by Sony Classical in New York. Those consoles were a bit awkward in terms of hardware requirements, because the BW-102 initially was designed for two-channel applications. Later, we also upgraded most of the modules to handle 96 kHz. Quite a few customers still use the BW-102, we even occasionally sell modules. Technically it is still up-to-date with 96/24 capability and 32-bit floating point processing.

After the BW-102, we started the Gambit Series with 19” units (e.g., analog to digital, digital to analog, parametric equalizer, dynamics processor, de-noiser/de-clicker, sampling rate converter, and more).

SHANNON: In 2000, Weiss entered the high-end consumer audio market with a new product line. What was the impetus behind that decision?

DANIEL: We thought that our DAC1 DAC could find a market within the high-end community. So we built the Medea DAC, based on the DAC1, to test the waters. The Medea became a huge success and it did not take long for customers to ask for more. So we built the Jason CD transport to complement the Medea. Other high-end products followed, up to the latest one, the MAN301 network player.

SHANNON: With the two separate aspects of your company—professional equipment for mastering studios and high-end consumer products—you are in the unique position of controlling, in part, the “production” of the masters and their reproductions. Do you think there is a direct correlation between the two “worlds?”

The Weiss 102 Series consists of digital audio processing modules suited for CD mastering, mixing, and digital audio signal processing. You can configure a system according to your requirements.

The Weiss 102 Series consists of digital audio processing modules suited for CD mastering, mixing, and digital audio signal processing. You can configure a system according to your requirements.

DANIEL: Correlation maybe in that both mastering engineers and audiophiles are interested in getting topnotch sonic quality and ergonomics. We can use our design philosophy—with the utmost transparency—with both markets. But in the end, we simply supply tools. The mastering engineer needs to know how to use them properly.

SHANNON: To what do you attribute your company’s continuing success?

DANIEL: At first, it was the fact that we built the right product at the right time (i.e., when the CD took off there was a huge demand for decent audio processing in the digital domain). In the consumer market, I think our customers like our “no bull” approach. I don’t hold back with my opinions about $1,000 mains cords, gold-plated fuses, small wood blocks for acoustics treatment, or CD demagnetizing, and so forth. I wrote some white papers firmly based on the laws of physics on various audio topics in an attempt to fight the snake oil with facts. This is something I like about the pro audio people, they are down-to-earth guys.

SHANNON: Tell us about your favorite high-end consumer product? What makes it different from other products on the market today?

DANIEL: One of my favorites is the MAN301 network player—from our product line, of course. It is an incredibly versatile unit for CD playback and ripping, and metadata tagging/artwork. It uses the Gracenote database and this is hardly seen on any other high-end network player. It also includes file playback (including DSD), DAC, preamplifier functions, and so forth. I use one at home and enjoy it every day. We continue to develop additional software for the MAN301 (e.g., for room equalization, creative equalization, vinyl simulation, and so on).

I also like to listen to as many different speakers as possible to explore the various philosophies and designs. I think the speaker/room system has, by far, the greatest potential for improvement of the whole audio chain. Audiophiles should acknowledge that and stop messing around with mains cords. The industry still has a long way to go when it comes to speaker/room optimization.

SHANNON: Could you share your opinion on mastering for digital file distribution and, in particular, the mastering for iTunes initiative?

DANIEL: If it is mastering for an uncompressed format, then the procedure should not be different from a standard CD mastering—except maybe if the format is at a higher sampling rate and/or word length than for a CD.

Mastering for iTunes is different, as it means mastering for a lossy format (for the time being at least). But I think the best thing about that initiative is Apple imposes specific criteria on the technical quality of the supplied music, in particular that the music must not be clipped. There are also a number of recommendations available at

The Weiss-designed MAN301 network player’s front boasts a sleek design. It is a versatile unit that uses the Gracenote database.

The Weiss-designed MAN301 network player’s front boasts a sleek design. It is a versatile unit that uses the Gracenote database.

SHANNON: Where do you see the audio market headed in the next five years? Do you think we will eventually evolve to “high-end” streaming audio services rather than downloading files?

DANIEL: There always will be both variants. Many people like to “own” the music so they can play it anytime and anywhere. And, I think the emotional relationship to the music is different if you’ve got it “on file” and not just via a stream.

Streaming services are great to check out new music. They should have a “buy” button on their websites though. Streaming during travel can get expensive and/or can be annoying when the stream gets disrupted in the tunnel or because of too many people try to get streams on a train, for instance.

Also it seems that for artists streaming services are far from lucrative. That could be changed maybe if they would simplify the buying process right from the streaming site.

In any case, the majority of high-end playback systems will use computer-based playback devices because it is so much more convenient and easily enables people to discover new music from streaming services or even in their own libraries.

Industry Watch: November 2013

Ray Dolby

Ray Dolby

Ray Dolby (1933–2013)

Ray Dolby passed away on September 8, 2013 at the age of 80 died after battling with Alzheimer’s and leukemia. While Dolby was mostly known for his work in noise reduction and electronics, his surround-sound invention had an enormous impact on the loudspeaker industry (see Photo 1).

Born in 1933 in Portland, OR, Dolby was raised in San Francisco, CA, and attended Sequoia High School (class of 1951) in Redwood City, CA. As a teenager in the decade following World War II, he held part-time and summer jobs at Ampex in Redwood City, working with the company’s first audio tape recorder in 1949.

While at San Jose State College and later at Stanford University (interrupted by two years of Army service), he worked on early video tape recorder prototype technologies for Alexander M. Poniatoff and Charlie Ginsburg. As a non-degree-holding “consultant,” Dolby played a key role in the effort that led Ampex to unveil its prototype Quadruplex videotape recorder in April 1956, which soon entered production.

In 1957, Dolby received his BS in electrical engineering from Stanford. He subsequently won a Marshall Scholarship for a PhD (1961) in physics from the University of Cambridge, where he was a Research Fellow at Pembroke College. After Cambridge, Dolby acted as a technical advisor to the United Nations in India. In 1965, he returned to England, where he founded Dolby Laboratories in London with a staff of four. In that same year, he officially founded the London-based Dolby Laboratories and invented the Dolby Sound System, a form of electronic filter. However, his first US patent was not filed until 1969, four years later. UK-based Decca Records first used the filter.

Probably his most famous invention was the surround-sound technology now used in movies, cinemas, PCs, and home theater equipment. Dolby Surround became well-known when two 1977 blockbuster films, Close Encounters of the Third Kind and Star Wars, used Dolby stereo technology as an essential part of the films’ appeal. Today, the bulk Dolby Laboratories’s revenue comes from technology licensing. Ray Dolby was #190 on the Forbes Fortune 400 list in 2012, the fruits of an amazing career.


Bob Diamond

Bob Diamond

Bob Diamond (1956–2013)

It is with great regret that I announce the passing of Bob Diamond, another outstanding member of the loudspeaker engineering community. Born in 1956, Diamond received his BSEE at the University of Wisconsin, Madison, WI.

He began his career as an Acoustical Engineer at International Jensen (1987). He joined JBL Professional 1987–1993 as a Senior Loudspeaker Engineer. Diamond then became the Chief Loudspeaker Engineer at Aura Systems/Aurasound from 1993–1995. He left Aurasound and formed Diamond Audio Technology, a company that bore his name, as president from 1995–2000. Diamond became the Director of Product Development at M&K Sound from 2000–2003, moving to Cerwin-Vega as a Senior Transducer Engineer from 2003–2005. From 2005–2007, Diamond again served as a Senior Transducer Engineer, this time at Nuventix.

From 2008–2011, Diamond held positions as Director of Acoustical Engineering, VP of Engineering, and President of Zylux America. He spent the last two years of his life caring for his grandson Corbin, for whom he was putting together a college education fund. His untimely death prevented this, but a group of friends and family have established the Bob Diamond Memorial Fund. To contribute, visit

I personally knew Bob Diamond. Our paths crossed on numerous occasions over the years at Aurasound, M&K, and Diamond Audio. He had a great sense of humor and was an excellent loudspeaker engineer.


THIEL Audio Hires Mark Mason

THIEL Audio, winner of more than 60 prestigious awards for loudspeaker design and performance since 1978, has appointed Mark Mason as the company’s new Director of Product Development. Mason represents the first in-house engineering presence for the brand since Jim Thiel’s passing in 2009.

Mason brings a depth of engineering experience combined with a range of technical capabilities to THIEL after nearly a decade as Design Team Manager at PSB. Mason’s expertise includes critical applications (e.g., driver design), Class-D amplifier design, and high-performance acoustic systems design. Mason said he was familiar with THIEL and he has tremendous respect for what the brand has achieved in the three-plus decades since it was founded.

Most recently, Mason was Director of Product Development for Specialty Technologies (SVS), where he was responsible for the company’s product management strategy and execution. Mason’s designs have garnered numerous prestigious awards including: The Absolute Sound Editor’s Choice, Sound & Vision Certified and Recommended, Best Home Cinema Room (S&V Bristol Show), Audioholics Consumer Excellence, Stereophile Recommended Components, and Electronic House Product of the Year.


Consumer Confidence Grows

Consumer confidence in technology spending reached the highest level in 2013, while sentiment toward the overall economy dipped in August, according to the Consumer Electronics Association (CEA). The CEA Index of Consumer Technology Expectations (ICTE), which measures consumer expectations about technology spending, increased by 1 point in August to 87.2. The ICTE edged past July’s level to reach the highest point so far in 2013. The CEA Index of Consumer Expectations (ICE), which measures consumer expectations about the broader economy, decreased 5.2 points in August to 162.6. The ICE remains 6.1 points lower than August of 2012.

The CEA Indexes comprise the ICE and ICTE and are updated monthly through consumer surveys. New data is released on the fourth Tuesday of each month. The CEA has been tracking index data since January 2007. For more information, visit

Q&A: Gregory Charvat – Early Curiosity Leads to a Lifelong Engineering Pursuit

Gregory Charvat created an intricate work station at his Westbrook, CT, home to design, test, and build projects.

Gregory Charvat created an intricate work station at his Westbrook, CT, home to design, test, and build projects.

Gregory Charvat—an engineer, professor, entrepreneur, and author—encourages people to explore the opportunities that come their way.

SHANNON BECKER: Your interest in amateur radio equipment began when you were young and continued through your high school years. Can you describe some of your first projects?

GREGORY CHARVAT: I grew up in the metro Detroit, MI, area, and I was very interested in electronics for as long as I can remember, almost naturally. As a young child, I wanted to understand where all the people and things on television came from. One day we took apart an old television set so I could see how it worked.

My mother studied electrical engineering at Lawrence Technological University, which is an engineering school outside Detroit. She occasionally brought me to her classes and labs. Later while she was working at Ford Electronics, she sometimes would take me to work on the weekends, which was super exciting because I was able to make circuit boards, use oscilloscopes, and so forth (this was maybe from age 10–13).

I learned how to use transistors at age 10. I became interested in CB radios. At about the same time, I helped my friends dust off CB radios from their parents’ attics and we built a very nice CB radio network. When I was about 13, I transitioned into amateur radio because my mother wanted me to try a more sophisticated hobby—one where you build your own equipment and  communicate across great distances.

My first electronics projects that I can remember involved building a large switch panel that ran off an old model train transformer to power a car radio, a fan, a light bulb, and other things. Next, I outfitted my bike with buzzers, lights, and a generator to power them with a rechargeable battery. Shortly thereafter, amateur radio became my main interest. I built a 2-m transceiver kit, a 2-m power amplifier kit, modified old police radio power amplifiers to work on 2 m, and many other things. In high school I became involved in a radio telescope project. My role was to upgrade the receiver to a more advanced scanning spectrum analyzer with analog signal-tracking circuits that I developed. Some of these circuits were later used in a friend’s dissertation at Michigan State University.

When I was 16, I interned at Aeroflex Lintek, a defense contractor, helping build radars used to measure the radar cross section of stealth aircraft. From there I became interested in radar technology and I was amazed that you could make images with microwaves. I recall repairing the rotator at Mission Research in Dayton, OH, testing low-noise amplifiers (LNAs) on an HP8510 network analyzer, building many boards, military-specification cables, chassis, mounting power supplies, and finding parts in catalogs for designs.

SHANNON: What is your current occupation? Are you still involved with Butterfly Network?

GREGORY: I am the co-founder of Butterfly Network, which is a privately held company that brings together world-class talent in computer science, physics, and electrical engineering to create an entirely new approach to diagnostic imaging and treatment. I lead the hardware team, which is our company’s largest group. We are responsible for the development of the hardware for the company’s first product.

SHANNON: Can you describe some projects you’ve done?

GREGORY: I built the first three prototypes, set up our lab and machine shop, recruited more than half the company, negotiated a number of contracts, and now I am learning about application-specific integrated circuit (ASIC) engineering. We are looking for an analog ASIC engineer and a chip packaging engineer, for anyone who is interested in working with me. I can be reached at I will reply to all e-mails.

SHANNON: Are you still instructing at the Massachusetts Institute of Technology (MIT)? Can you describe the courses you teach?

GREGORY: My Build a Small Sensor Radar course continues to this day. In June, it was offered as an MIT Professional Education course. Numerous universities have adopted this course as either a capstone engineering project or full-semester course. Private institutions and government labs have also adopted the course for internal training. The coffee-can radar project has even made an appearance on Mongolian National Television as part of an MIT EdX program a friend of mine ran last summer. You can now buy the coffee-can radar project as a complete kit from Quonset Microwave.

Additionally, two other Build a Radar courses were developed from the original course including Build a Phased-Array Radar and Build a Search and Track Radar, but I am no longer teaching these courses. My relationship with MIT has evolved into me being an advisor for the Camera Culture Group at the MIT Media Lab where we experiment with two interesting technology threads.

SHANNON: You have a main website, a blog, Mr. Vacuum Tube; several YouTube videos; and an active Twitter account. What types of projects do you typically share?

GREGORY: I like to read other people’s Twitter posts and blogs and I watch  YouTube videos. I appreciate the time and effort other enthusiasts put into sharing their work. To this end, I like to share what I am doing and maybe it can help someone someday. For this reason I try to share everything I can, from symposiums that I am involved in to topics in my book, to papers I am publishing to hobbyist projects (e.g., vacuum-tube audio, antique radio restorations, clock and watch restorations, and sailing adventures).

As an undergraduate, I learned from a math professor friend of mine that you must publish everything you create, otherwise the knowledge will be lost.

SHANNON: You are a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE). What does your involvement entail?

GREGORY: I’m a huge fan of the IEEE. The IEEE organization maintains high academic standards for papers in its journals and symposiums and I really appreciate that. IEEE members are the archivists and storytellers of electrical engineering history, past and present. To help out, I was chairman of the IEEE Antennas and Propagation Society Boston Section for two years. Our meetings went from 12 attendees each month to 40 by my tenure’s end. This was achieved by the use of social media and the lineup of fascinating speakers. I then became a Member-at-Large for the IEEE Boston Section’s Executive Committee in 2012. Additionally, I was on the steering committee for the 2010 International Symposium on Phased-Array Systems & Technology. I am currently on the steering committee for the 2013 symposium this fall in Waltham, MA.

SHANNON: You have authored many articles, including a two-part audioXpress series, “Vacuum Tube Home Theater System” (May–June, 2012), about building a “monster” system with 23 vacuum tubes. Tell us a little about the system. Have you made any upgrades or adjustments?

GREGORY: This system was originally developed in the summer of 2001 while I was a junior undergraduate. It was deployed in my dorm room. The feedback compensation networks were upgraded in 2003. The power supply was upgraded in 2005 and I moved to a direct grid-bias configuration to get more power out of the amplifiers.
In 2009, I again upgraded the feedback compensation networks. This system is in our living room and it is used almost every day. It is currently in a maintenance posture, where I occasionally have to replace one of the original tubes from 2001. Recently I had to replace a high-voltage rectifier diode. I’m due to replace the pentodes on the subwoofer amplifier within the next few weeks.

SHANNON: Your forthcoming book, Small and Short Range Radar Systems, is slated for publication in February 2014. What can readers expect to learn?

GREGORY: This will be the first book on small and short-range radar devices. My goal for the book is to show readers how they work, how to build something practical, and do it quickly.
I want to show readers the high-level basics and how to do a back-of-envelope estimate to determine if a system is worth developing. I also wanted to provide working engineering examples of each type of short-range radar, including complete schematics, diagrams, bill of materials (BOM), a demonstration video, data for the reader to process from that video, and usable MATLAB scripts. I also discuss the practical aspects of design so these examples can be scaled to other applications or expanded.

As engineers, we are applied scientists. We use our understanding of physics to build something tangible to help humanity. This book facilitates that process for short-range radar sensors.

Gregory’s go-to vacuum-tube transceiver is a 20-m single-sideband (SSB) of his own design.

Gregory’s go-to vacuum-tube transceiver is a 20-m single-sideband (SSB) of his own design.

SHANNON: Tell us about the amateur radio station you designed.

GREGORY: After hearing stories about a friend of mine at the MIT Haystack Observatory, who as a teenager built his own radio out of one type of transistor his father was able to “borrow” from work, I decided to redo this exercise myself. I developed a shortwave receiver out of one type of transistor. It was a fascinating experience.
From there, I decided to develop my own single-sideband (SSB) transceiver design from scratch. I built a 20-m SSB radio with 40-W peak-envelope power (PEP) that is extremely sensitive. It was an amazing experience to contact Western Europe with a radio that I developed myself!

Shortly thereafter, the American Radio Relay League (ARRL) issued the Homebrew Challenge III, to build a 10-m and 6-m SSB/CW transceiver for less than $200. I took this challenge and submitted a working radio one day before the contest ended. Apparently mine was one of only two submissions. The other was late, but I blew the budget at $450! (It’s really about the experience, not the cost.) I was given honorable mention and an article in QST magazine for my efforts. More importantly, I had the pleasure of getting to know some of the folks at ARRL.

Most recently, I developed a way of tying a SSB transmitter to an R-390A, which is the tube era’s best communications receiver and highly sought after by collectors. An article on this modification will run soon in QST’s “Hints and Kinks” column.

In summary, my homemade amateur radio station consists of a 20-m SSB radio, a 10-m and 6-m SSB/CW radio, and an R-390A that is tied into the 20-m radio for when I want to run in “boat anchor” mode.

SHANNON: If you had a full year and an ample budget to work on any design project you wanted, what would you build?

This homemade amateur radio station evolved from an idea to construct a shortwave receiver out of one type of transistor.

This homemade amateur radio station evolved from an idea to construct a shortwave receiver out of one type of transistor.

GREGORY: If I had a free weekend in the summer I’d sail to Long Island, NY. If I had a free weekend in the fall, winter, or early spring I’d restore a vintage mechanical wristwatch. If I had a free week I would restore the vintage all-tube Telefunken stereo receiver in my office. Or, I’d combine a 1970s solid-state amateur radio transmitter with my R-390A. If I had one to four months, I would bring to close the projects I am helping with at MIT’s Media Lab.

After that, I would look for something long term. I would probably brainstorm with some friends about a new idea for a fun research project or a startup. Generally speaking, I would like to have one long-term project moving steadily along while also closing numerous shorter-term projects along the way.