{{< MultiGalleryComponent galleries="1974-superboard" >}} In 1973 we decided to build a new studio style mixing console. Our first studio style console had been designed and built by Maxson and Chuck Conrad in 1970-71, but we only built one of those units. Maxson and I wanted to build a state-of-the-art studio style mixing console designed specifically for live sound. We discussed the idea with Jim Bornhorst and Jim said that he could design the console using the new integrated circuit chips that were becoming available from companies like Intel and Texas Instruments. Jim said that he had an idea for building a totally variable “parametric” equalizer where the frequency selection was continuously variable and the width of the boost or cut frequency range or “Q’ was also continuously variable. Maxson and I shared an office at the 9011 Governors Row building, and we asked Jim to come off the road and setup an office and lab in the building. I setup a design area with a drafting board and a large flat file cabinet to hold mechanical design drawings. The plan was for Maxson, Brutsché and Bornhorst to develop the specifications for the console and Jim would do the design of the electronics and I would do the mechanical design. I also was the project manager. I handled all of the purchasing, created the bill of materials and kept track of the costs for the materials, parts and labor to build the console.

{{< StoryImage id="showco-2-equipment-014-equipment" caption="Superboard with walnut panels and VU meters for submasters and outputs 1974." credit="© Jim Bornhorst Archive" size="responsive" >}}

## Development of the Showco Superboard - An In-depth Discussion by Jim Bornhorst The Superboard was one of the most satisfying projects I worked on during my long career with Showco. After being recently hired as a sound engineer for Showco in 1972, it was a dream come true for me to be involved in such an important audio project. I was fresh out of college with a degree in Electrical Engineering from Texas A&M University and never imagined that I'd end up in a field that had been my passion since grade school, professional audio. Showco co-founder Rusty Brutsché and his partner, Jack Maxson, conceived the basic console layout over quite some time in 1973. Up until that time, Showco had been using rack mount, 6-input solid state mix modules that had been designed and built in house by Chuck Conrad, Showco’s electrical engineer at the time. These had been architected to mimic a Grommes G5M commercial unit that Showco initially bought for mic mixers. Four of the 6-channel “Yellow Mixer” rack modules were mounted in a double wide rack providing 24 mic inputs and 4 sub-masters to drive the PA system. There were also bass/treble tone controls and a couple of monitor sends per channel but it was pretty hard to mix floor and side monitors from front of house! Maxson used the only "desk style" console built by Conrad in ’71. He used it primarily on Three Dog Night as it had a more professional layout and advanced features for the then prestigious band. The purpose of the Superboard development was to put Showco in the forefront of the emerging touring rock-'n-roll business with proprietary equipment. Rusty and I worked on the physical console design exclusively and together through many late-night hours. Rusty, a degreed Mechanical Engineer from SMU, did the mechanical designs and I did all of the electronics design including all printed circuit board layouts. A third employee, Ron Fox, provided the walnut case work, the aluminum frame and road case design. We were a good team. We began on the project in late 1973 and had the first one going in October 1974. None of us will forget the minute we fired the console up for the first time. And it worked! We listened to a tape recording of Walter Carlos’ “Switched-on Bach”, turned out the lights in the lab and passed around a bottle of wine. We savored the lighted meters, smooth control response and the revolutionary new LEDs scattered all over the front panel! It sounded really great too. ## The First Superboard Show and Grand Funk Railroad 1974 Rusty, Ron and I had just completed building the first Superboard in the fall of 1974. It was to go out on a tour with Grand Funk Railroad which was already in progress. Andy Cavaliere, the group’s manager, had paid $10,000 for the honor of being the first to use the Superboard on a live event. The console was thoroughly tested in the shop but fortunately, some foreseeing person, probably Rusty, decided to send it out on a short gig for a trial run before putting it into full service. The arrangement would test the new board and allow us to hear how it actually sounded in an arena environment with our PA system. Grand Funk had been touring with our standard Yellow Mixer double rack console and all was going well. I don’t recall who the Front of House sound engineer was but whoever it was turned out to be very understanding. The console was trucked to somewhere in the Northeast and I flew to the gig to babysit the new Superboard. I unpacked the board from its road case and set it up on a low riser out in the arena. I remember setting up directly across the empty arena from the sound riser with the Showco yellow mixer rack console which was on the right side of the floor. It seems like a sound check was going on that afternoon because people were milling around and curiously examining the new Superboard. Among them was Andy Cavaliere. Thank goodness we hadn’t disconnected the yellow mixer console because when I switched on the Superboard’s power ALL of the power supply fuses blew instantly. Cavaliere looked at me with this WTF look and began yelling: “What had we done? Why did we jeopardize his tour?” and on and on. I was beyond mortified and began checking out the board while trying to calm Andy down. I assured him his show had not been jeopardized, after all, the yellow mixer console was just over there still working fine. I discovered that the 120 VAC line fuses were still intact so I reasoned that something catastrophic must have happened inside the chassis and that I hadn’t done something stupid like applying 240 VAC to the beast. I assured Andy and the others in the small crowd that had gathered that I would figure it out and fix the problem, just give me some time and a place to work. We wheeled the console in its case into a back dressing room and I went to work disassembling the board. It was probably near 5:00 PM by this time and I sure wasn’t hungry. What I discovered produced a head-slapping moment of relief that I’ll never forget. In the back of the console, under the meter bridge, was a printed circuit motherboard that carried all of the audio summing busses as well as all of the power supply lines on its surface. These traces fed DC power to the microphone modules, meters and lights. The copper circuit traces were bare copper because we hand soldered multi-cables leading from each module to the board instead of using a rigid connector. A wired pigtail was deemed more reliable as we had problems in the past with connectors. Since the console travelled in its case with the mother board at the bottom, any debris inside the chassis migrated that way, down. I found the mother board littered with aluminum shavings we had failed to remove after we had drilled holes and filed and clipped on stuff during construction. Since ground traces ran on the mother board between the DC power traces, shorts to ground were highly likely. Thank goodness Tom Walsh had fused everything in his power supply. I spent the rest of that evening taking every subassembly out of the chassis and meticulously vacuuming out all of the chips and other detritus. I didn’t get to see a second of the show but when I reassembled the console and replaced all the fuses it powered up and ran just fine. Another thank goodness for a complete tool kit and spares of everything. We later installed protective foam covers over all the motherboards in the consoles and never had another incident, at least not like that one. The next day at another venue we tried again, before Andy showed up. The console came right up and I think was used for the show that night and for the rest of their tour. That second day is just a blur now but I do remember seeing a remarkable new invention built by Jim Fackert, the boffin of the tour. He was showing his Cyclops, an up-shining spotlight with a remotely controlled mirror attached to the front that he used to direct the beam. There was one Cyclops on each side of the stage hiding behind the amp line. Operators with a joy stick controlled the mirrors and maybe the color frames by pushing buttons. I clearly remember how hauntingly eerie the beams were because they looked like they came out of thin air. His invention was harbinger of things to come! {{< StoryImage id="showco-2-equipment-048-equipment" title="The Superboard" caption="Superboard Power Supply with Motherboard and Pigtails." credit="© Jim Bornhorst Archive" size="medium" >}} ## Technical Specifications and Engineering Electronically, the Superboard was an all IC op-amp console. I was hesitant to go against the "audiophiles" who said that ICs could never be quiet enough or fast enough for a professional console. But I believed that the secret was in designing a low-noise front end, a fast and quiet mic pre-amp with its 60dB of gain. If that could be made quiet, then the line level circuit ICs wouldn't add much noticeable noise. This was for rock-'n-roll anyway. Who'd notice a little noise! After quite a bit of research, I focused on the Fairchild µa739 dual op-amp which was a stereo, magnetic phono pre-amp chip. I learned how to stabilize the circuit while keeping the S/N ratio at 60dB or a bit better. This was tricky working at 600 Ohms as the chip wanted to oscillate since it was designed for a 10K Ohm input impedance to match phono cartridges. The first amp in the dual package was used as a differential pre-amp accepting the balanced mic signal that put out about the same signal level as that of a magnetic phono cartridge. This stage provided up to +60dB of gain. The second op-amp was a unity gain buffer feeding the rest of the module’s circuitry. Variable feedback around the two gave us the gain or “pad” pot for adjusting the amplification of the front end. I used a 555 timer IC to sample the buffer output. This comparator was calibrated to kick the "clip" LED when the input levels were close to clipping. Phantom power for condenser microphones was provided over the differential mic lines. We later learned to add input transient protection to protect the µa739s from spikes created while plugging and unplugging mics with phantom power on. But that's another story. Parametric equalization was not a part of Maxson's original concept. I conceived of the EQ while experimenting with tone control circuitry in the lab during console electronic development. It is based on the now common state-variable filter which became fairly easy to implement with integrated op-amps. It took a little convincing to get Rusty and Jack to include the new tone control in the console design. We were aware that it had never been used before in an audio product and they were rightfully skeptical. The heart of the concept was that all characteristics of the three-band tone control circuit were to be continuously variable; gain, frequency and bandwidth. Tone controls of that time allowed the user to select only a single band of frequencies to emphasize or deemphasize and the filter bandwidths were typically fixed. I mocked up one channel of the EQ for Rusty and Jack to listen to and that did it. We had the ability to select either a shelving or band pass filter shape for the bass and treble bands. The shelving equalizers were much like conventional tone controls while the band pass filters worked around a specific frequency. The mid-frequency filters were bandpass only. Of course, the slope of the shelving curve was continuously variable as was the Q, or bandwidth, of the band-pass equalizers. You could cut or boost each of the three bands by ±15 dB and continuously sweep the filters’ affected frequencies over quite a range in each of the three overlapping bands. The effect of the mic equalizer was overwhelming. It allowed the operator to “tune” the tone as one would tune a radio. It felt completely natural to dial in the exact sound an operator was looking for. Additionally, troublesome feedback, a common problem in sound reinforcement, was easily quashed with the turn of a knob! Another attribute of the design was the summing buses that added, or proportionally mixed, all of the microphone module signals together depending on the position of the mic fader on each channel module. Since the quadraphonic sub-masters and Quad Output module all had IC amps in them, I could use the inverting inputs of these op-amp stages as virtual grounds or summing nodes for all of the signals coming together inside the console. This summing scheme was lossless and negated further amplification downstream. There was a long mother board in the back of the console connecting all of the modules via hardwired pigtails and gold plated connectors. It had all of these summing busses, along with DC power busses, running all along it. The mic modules all output to the appropriate submaster bus via sub-master select switches. Each mic module could simultaneously output to two of the eight summing busses for stereo operation. The sub-masters output to the 4-channel Quad Master summing buses via a quadraphonic panning joystick which allowed the operator to sweep the sound from that sub-master around the room. I was very worried that these long busses would pick up noise or have crosstalk but the virtual ground provided by the op-amp summers kept the impedance at 0 ohms so induced noise common to high impedance circuitry was a non-issue. The thing was damned quiet! Three monitor sends were proportionally sourced from each mic module by three individual pots. These signals were summed at the three monitor modules in the upper center portion of the board. Each mic monitor send could be selected to pick up the signal before the module fader and EQ, before the fader but after the EQ, or after the fader and EQ. These monitor sends allowed three additional independent mixes to emanate from the Superboard which greatly enhanced the console’s flexibility. The console included an intercom module that connected with an on-stage signal-light box through the console snake. You could feed monitor signals into the intercom so the house mixer and monitor mixer on stage could both hear the same mix. The monitor module also summed all of the solo switches for the mic modules so that the front of house mixer and monitor mixer could both hear what had been soloed on the console, a very useful feature during troubleshooting. A tape input module had quadraphonic inputs so that prerecorded music could be played before and after the show. The tape module had 4 channels of fairly conventional shelving bass and treble EQ which sounded pretty good. The console was also fitted with two Monophonic Output modules to feed house PAs, TV trucks or local radio stations. The console back panel had a patch bay of insertion points for patching effects devices into every mic, sub-master, and output module. There was also an array of 3-pin XLR serving every mic module and board output that turned out to be very useful in recording situations. We used a 81 pin Cannon oil field connector to connect the mic snake which led to a microphone j-box onstage. The drive lines for all of the outputs were in a similar Cannon 27 pin connector on the back of the Superboard that connected a second drive snake in the Superboard accessory rack with the stage electronics and power amplifiers for the speaker stacks. The console had a built-in linear power supply designed by Tom Walsh supplying the proper voltages to all the lamps, ICs as well as microphone phantom power. I had a go at a power supply design but it hummed and I was never able to correct the issue. Tom saved my butt. The goal was high reliability, very low noise and short circuit protection. This was the only module of the console that did not have some sort of built in redundancy. If the power supply blew, you were down. Although Showco generally toured with a spare power supply, changing this module out during a performance required an unreasonable amount of time. The simple linear design was remarkably reliable and robust but very heavy. Anecdotally, a console supply was fried once when it was inadvertently connected to 240V. The system engineer (Buford??) did the show using two 12V car batteries powering the ICs. The meters were dark. The Showco Superboard was the first console with full parametric equalization for every function. Late in '74 Rusty and I attended the 46th Audio Engineering Society convention in New York where I met the now legendary studio engineer George Massenburg. George was building his reputation as a studio guy and was showing his revolutionary 3-band parametric module for studio use. The paper he presented to the AES that year on parametric equalization was a block-buster and cemented his career. It was a single channel unit housed in a 7 inch rack module and was to sell for thousands of dollars. George had implemented his studio quality EQ using discrete transistors gaining him 30dB of noise margin over my design, a very impressive accomplishment in my opinion. I thought I had invented parametric EQ but was very pleased to discover that George and I had been going down similar paths. As with many great inventions, parametric equalization’s time had come. We ended up building a total of 8 consoles over the next couple of years. Five were a second generation design incorporating a new op amp from Texas Instruments, the TL 072 and TL 075. These dual and quad packages used a Bi-FET technology that incorporated integrated P and N channel FET transistors in the front end of the amps. The FETs were 10 times faster and more than 3dB quieter than the old all-junction transistor Motorola’s 741s. The faster slew rate Bi-FETs really improved the high frequency response of the consoles and the noise improvement was quite noticeable as well. I also replaced the old, dim red clip LEDs on the mic modules with a bright new, and very cool, bi-color red/green LED. It changed color if you reversed the current through the device. I made a great “signal present” indicator in green and a bright red “clip” indicator in red. A 556 dual timer IC sensed levels and drove the LEDs directly. Some of the Superboards were on the road for over 20 years and were extremely reliable. They were used on every first tier act of the day, from Aerosmith to Led Zeppelin. In 2020 Superboard A was donated to Chuck Conrad’s Texas Museum of Broadcasting in Kilgore Texas where it has a prominent position is his impressive collection. It was about to be scrapped, doomed to the same fate of its seven brothers, when George Wheatly called asking if I wanted it. Obviously, Rusty and Jack were proud of our accomplishment. The Superboard did help put Showco at the forefront of concert touring sound reinforcement and also stimulated lots of competition. It provided millions of concert goers with top notch sound quality at live events throughout the world, provided the signal source for countless live recordings and provided a launching point for the careers of many now veteran sound engineers, including me. JMB April 9th, 2025 ## Live Recording Credits (a partial listing) - **King Biscuit Flower Hour** — Willie Nelson and other artists - **Linda Ronstadt** — @ The Universal Amphitheater, LA, CA (1976) - **Paul McCartney** — *Wings Over America* Tour (1976) - **Jackson Browne** — *Running on Empty* (1977) - **Willie Nelson and Family** — Live @ Lake Tahoe (1978) ## Rusty Brutsché Superboard Comments We decided that the unit would have 30 inputs and eight submasters and that it would have quadraphonic outputs with quad pan pots on the submasters. The Who’s Quadrophenia Tour was touring in 1973 with a quadrophonic sound system where the speakers were setup in the four corners of an arena and we thought that might be a trend for shows in the future so we specified our new console to be capable of supporting a quadrophonic sound system. It turned out that quad sound systems did not become a trend and we later replaced the quad panners on the submasters with stereo pan pots. We started the specification process with Maxson doing a rough hand drawing of the input module and then I would do an engineering drawing at 1:1 scale of the module panel with the controls and artwork for the module front panel and Jim would decide if the proposed functionality could be implemented with his electronic designs. The design evolved to eight lighted pushbuttons mounted on a separate panel at the top of each of the 30 input modules to assign the module to one of eight submasters. Each input module would have a transformerless balanced low impedance microphone input with 60db of gain, a three-band parametric equalizer with continuously variable frequency selection and boost/cut frequency width or “Q” and high and low shelving EQ with continuously variable cutoff frequencies, two monitor sends and one echo send each with pre (before fader and EQ) pre EQ (after fader no EQ) and post (after fader and EQ) switch, input pad and overload LED, stereo pan pot, solo switch, and a linear slider control for volume. We chose a mechanical slider named Slidex by a company named Audio Designs. The Slidex used a twisted metal helix connected to a sealed rotary potentiometer and the linear sliding mechanism moved up and down the helix and turned the pot to vary the volume of the input module. It was a very robust design and it provided excellent resistance to dirt, dust and liquids.

{{< StoryImage id="showco-1-people-027-showco-people" caption="Jim Bornhorst at his light table designing the Superboard 1974." credit="© Jim Bornhorst Archive" size="responsive" >}} {{< StoryImage id="showco-1973-showco-people-hrb-superboard-73-2" caption="Rusty Brutsché designing Superboard input module panel 1974." credit="© Rusty Brutsche Archive" size="responsive" >}}

{{< StoryImage id="showco-2-equipment-051-equipment" caption="Superboard input module with Slidex slider 1974." credit="© Jim Bornhorst Archive" size="responsive" >}} {{< StoryImage id="showco-2-equipment-015-equipment" caption="Showco Superboard 1974. The eight submasters with the quad pan pots were in the center of the console. The eight lighted switches to assign the input modules to the submasters are mounted in the panel above the input modules. The modules above the submaster modules in the center are left to right, two monitor send master modules with EQ and master volume, one echo send master module with EQ and master volume. All three send modules could be patched via the patch bay for echo and other effects machines, stage intercom and solo controls, tape input, two mono output sliders and (not shown), a Quad Master output volume slider." credit="© Jim Bornhorst Archive" size="responsive" >}}

I made blueline copies of all of the front panel components, Ron Fox built a plywood mockup of the entire console and we glued the blueline copies to the top surface of the console so that we could get a sense of the proportions and how the finished design would look and feel. We also commissioned an artist’s color rendering of the console from a Dallas artist, Robert Shaw. After seeing the artist’s rendering, Maxson named the new console the Superboard. {{< StoryImage id="showco-2-equipment-056-equipment" title="Conceptual Vision" caption="Artist’s Rendering of the Superboard done by Dallas artist Robert Shaw during the concept stage of the project 1973." credit="© Jim Bornhorst Archive" size="large" >}} From a mechanical design perspective, I wanted to build an extremely robust product that would be reliable, have a very long service life and handle the rigors of touring and being hauled around in trucks. We made the input modules 1 ½” wide and I used 3/16” thick 6061 aluminum for the front panels. On the back of the front panel, I designed a U-shaped chassis that connected to the front panel with screws and had side covers that fit into slots cut into the back of the front panel to create a totally sealed module. The PC board fit inside the chassis and was attached to the chassis with screws and to the front panel by the pots and switches on the module. We used DB connectors with gold plated pins with a wired pigtail to connect the input modules to a motherboard in the console. (We learned our lesson from L.A. Krause’s cadmium plated pins in the power amplifiers that oxidized and stopped passing the audio signal)

{{< StoryImage id="showco-2-equipment-020-equipment" caption="Pigtails with DB connectors for input modules wired into a motherboard." credit="© Jim Bornhorst Archive" size="responsive" >}}

Ron Fox built an aluminum frame that formed the mechanical structure of the console. He had a custom aluminum extrusion made that held locking #10-32 nuts, and he used that extrusion to construct the frame. All of the panels and the power supply connected to the frame using countersunk head hex drive #10-32 screws fastened to the captive locking nuts. Ron built the wood side panels with the hand hold cutouts and the wood panels on top around the VU meters out of solid ¾” thick South African walnut. Ron used a piece of ½” Baltic birch plywood on the bottom of the frame and he built a storage compartment under a folding padded arm rest to hold accessories such as four gooseneck lights that attached to the console. We lined the inside surfaces of the console with copper screen for shielding. Ron built a road case for the console using a custom aluminum extrusion that was welded together and had slots for fiberglass coated plywood panels. The case proved to be extremely durable and rugged because the console itself was very heavy and required four men to lift it in and out of the case. Ron also built a custom aluminum folding table and aluminum bench that we carried with the Superboard to hold the console and for the sound engineer to sit on during use.

{{< StoryImage id="showco-2-equipment-014-equipment" caption="Superboard with walnut panels and VU meters for submasters and outputs 1974." credit="© Jim Bornhorst Archive" size="responsive" >}} {{< StoryImage id="showco-2-equipment-050-equipment" caption="Tom Walsh designed an analog linear power supply for the Superboard." credit="© Jim Bornhorst Archive" size="responsive" >}}

Also mounted on the back of the Superboard was a panel with 30 XLR mic input connectors connected to the input modules, XLR connectors for the quad outputs, mono 1 and 2 outputs, the three effects outputs, and the headset output, an 81 pin mic snake connector connected to the input modules 1-27 and a smaller 27 pin connector to connect to the remaining three mic lines and all of the outputs from the console to the accessory rack with the master crossover panels. A second 27 pair snake connector was mounted in the accessory rack for the drive lines and other outputs from the Superboard and master panels. Another panel on the back held a patch bay that was wired to each input module, submaster and all of the outputs to enable external effects equipment to be inserted into any of those modules. And finally, there was a panel with 30 XLR recording outputs from each input module for connecting to a tape machine such as our Studer 24 track machine that was used for live recordings. {{< StoryImage id="showco-2-equipment-019-equipment" title="Patch Bay & Outputs" caption="Superboard patch bay and XLR recording outputs." credit="© Jim Bornhorst Archive" size="large" >}} The Superboard was a huge success for Showco. We built eight consoles and they were used for over 10 years on thousands of shows. We started the project in late 1973 and we completed the first unit ten months later in October of 1974. Each console cost about $20,000 ($150,000-160,000 in 2025) to build for parts and labor. The reliability and road worthiness of the Superboard exceeded our expectations with virtually no failures during the years they were used. The first console we built, Superboard A, is now in the Television and Broadcast Museum in Kilgore, Texas and it still works perfectly after 51 years. Jim Bornhorst’s parameteric EQ was the first of its kind in the live sound industry and it set the standard for all of the consoles that followed the Superboard. We purchased a Studer 24 track tape machine that we connected to the record outputs on the Superboard and we recorded several live albums including Paul McCartney’s Wings Over America live album and Jackson Browne’s Running on Empty album. I share Jim’s feelings that the Superboard was one of the most satisfying projects that I ever worked on. {{< StoryImage id="showco-2-equipment-055-equipment" title="Superboard A" caption="Jim Bornhorst and Chuck Conrad with Superboard A that Jim donated to Chuck’s Television and Broadcast Museum in Kilgore, Texas." credit="© Jim Bornhorst Archive" size="medium" >}}

Showco History