Story behind Boonar Tube Deluxe Project 2/3

Since my initial idea of simply adapting the original Boonar circuitry to accommodate tubes and a simple screen for time readout was a no-go, I scrapped it all and started from scratch. The Boonar Tube Deluxe required much more. The first thing I needed to do was to summarize the feature set that the new unit must have.

Given the important role of Echorec’s preamp in the sonic puzzle, I aimed for an audio signal path based on triode vacuum tube design. The tube’s plate and grid require higher voltages to bring them within their intended headroom and THD parameters, so I excluded the "starved plate" design and opted for a more complicated high-voltage power supply. That required the development of internal voltage step-up circuitry to achieve operating voltages of over 300V.

For an authentic Echorec experience, integrating the EM81 magic eye tuning indicator tube and its dedicated driver circuitry was indispensable.

Although my intention was to faithfully replicate the Binson® Echorec® 2 T7E model, I opted for a more elaborate playback heads switching system from the P.E.603-T model. This system includes individual switches for playback heads and their corresponding feedback networks, providing a wider array of possible combinations.

To enable full MIDI and presets functionality, every analog user-adjustable parameter required digital control. Additionally, another feature I believed was crucial was a USB port for potential firmware updates.

This expansion in features required developing proper menu software, so I opted for a 1.3” OLED screen instead of a simple 7-segment one. This, in turn, called for the design of a dedicated graphical user interface.

To make it a real studio-grade device,  I incorporated a separate "wet" balanced and transformer-isolated output for direct recording, alongside an external input for tap tempo/remote control/expression pedal control of all potentiometers.

Developing a product with such an extensive setlist of features requires significant R&D time, funds, and know-how; big companies typically have a dedicated team of top engineers for such tasks. Being the sole electronics engineer in our small family-run company, I realized that I’m going to need to acquire additional skills to apply these new technologies effectively.

Studying tons of professional literature and improving coding skills was a time-consuming but very fun process, and getting the first prototype segments with new technologies to work was promising. Some days I would easily spend 16 hours a day in the workshop. My wife, Jelena, was slowly going crazy because we needed to juggle between taking care of the company, building and selling our pedals, R&D and having time for the family.

Of course, not everything went as easily as I planned. Moreover, a substantial number of things took a more challenging and unexpected path.

When dealing with very high voltages and high headroom analog signals, careful selection of digital control electronics is essential. General-purpose parts didn’t work well; they were noisy or distorted quickly and in an unwanted way, leading to the first prototype PCB being discarded. So, I opted for the best professional ones I could find; however, unfortunately those parts come with a high "audiophile" price tag too.

Also, it is necessary to be very careful when mixing such analog signals with very fast digital ones; unwanted noise easily couples in from a whole spectrum of sources if electronics are improperly engineered. Different parts inside the unit required various voltages to work optimally, including dangerous ones up to 350V DC, so PCB routing of such complex circuitry also required meticulous design. Two more prototype PCBs were thrown into the trash bin. At one time, I was almost convinced I had a small ghost living in the pedal and making occasional parasitic noises for fun.

The electronics for the planned chassis installation required me to design and order custom potentiometers, rotary encoders, knobs, screen modules, and finally a power supply adapter. I obtained wall adapters from several global manufacturers with enough "juice" to power the Boonar Tube Deluxe since the device draws almost 800mA of current. They all promised well-filtered operation for audio purposes, but they each gave unsatisfactory results. I wanted it to be a dead-silent, studio-grade, so I took time and developed our own switched-mode power supply adapter circuitry with extremely low ripple voltage and noise.

The next task was to revise the virtual magnetic drum DSP design. Anyone who has ever had the fortune to own or try the original Italian Binson Echorec knows what an endemic beast it is, to say the least. Nothing beats its magical tone when the repeats are pushed to a point where they start to slightly overdrive, bubble, and melt together. The device becomes an instrument on its own, reproducing a cavernous, reverb-ish, and nicely filtered echo, never muddy or interfering with the original tone. This is almost all due to the machine’s unique memory system – steel magnetic drum medium, write/playback/erase heads and the way they are set, memory drum drive, all the imperfections that develop over the years of use, etc. Addressing and capturing all those nuances and transferring them as faithfully as possible to DSP is a paramount in order to successfully emulate the original Binson Echorec's character. I was very satisfied with how I did that with the original Boonar, however, I decided to go down the rabbit hole again. Two months later I had completely updated the DSP design.

Acquiring enough NOS magic eye vacuum tubes to even make it a viable project was a story for itself. It was a real quest. I personally visited several countries, including an old factory in Serbia, former Yugoslavia - EI Nis, made a million telephone calls and e-mails across the globe, and spent a small fortune to build a certain stock. Crazy, some would say, but I was so determined to make it 100% authentic that I didn't want to make any compromise. And it was kind of fun and adventurous. 

When I was finally satisfied with the design and was preparing for the first serious tests in the studio, the Covid-19 pandemic paralyzed the world. Sourcing electronic chips also became highly questionable, and their prices skyrocketed. This situation made me pause the project and wait for better times.

Fast-forward one more year, involving numerous extensive tests in the studio and unexpected design issues leading to the discarding of one more PCB design, I was finally completely satisfied. It was ready to be sent to David Gilmour for the final testing. The best quality control one could get, many would agree.

To sum it all, this project was as equally exciting as it was challenging for both me and the company. I had such great moments of creativity and enthusiasm, yet there were times when I’d hit the wall, needed a mental break, and days I wanted to give up. Many times I wondered if I got too carried away with it all and if I really need to go into such dubious details, but I guess my fanatical obsession with the Binson Echorec magic drove me forward. I knew that if I was going to get it right, I must leave no stone unturned.

In the end, I believe it made me a better engineer and taught me, sometimes through challenging experiences, the virtues of persistence, patience and discretion. 

Oh, and my wife hasn't left me. And we got a baby five months ago. :)

Zoran

David Gilmour studio photos courtesy of Polly Samson
Names Binson® and Echorec® are registered trademarks of their respective owners