Good echo chambers were difficult and expensive to build, especially in urban locations where real estate was expensive and extensive sound isolation was needed to keep out traffic and other noises. Tape loops were sometimes used but they didnt provide the random, complex reflections that were needed to replicate real reverb in an acoustic space. As for springs...well, they sounded like springs.
In 1972, EMT released the very first digital reverb, the rack mount 144. The capabilities of this early unit were limited, and few survive. But just four years later, EMT blew a lot of minds by introducing the 250 Electronic Reverberator Unit. It looked like something from an UFO, and sounded fabulous. A free standing unit, it was three feet tall with black radiator heat sinks on three sides and a large, bright red power supply assembly. On the upper control panel, 4 oversize levers resembling aircraft controls adjusted main delay/decay time, LF and HF decay times, and added delay to the send. The software also included delay, phasing, chorus, slap, and space echo programs. It had one input and either 2 or 4 outputs, depending on the version ordered.
Despite its early 12 bit architecture, the 250 had a beautiful sound. Its design was a joint effort between EMTs engineers in Germany and a small firm in Massachusetts called Dynatron. EMT designed the converters, I/O, and power supply, while Dynatron designed the main digital/processor board. The Dynatron effort was led by Dr. Barry Blesser, then a professor at MIT (and later an AES President). The finished unit had nearly 500 ICs, and 3 cooling fans. To protect its revolutionary design, the part numbers and identification were scratched off most of the ICs on the digital board.
Four years later EMT released the 16-bit 251. Along with a new reverb program and an LCD display, the 251 had extended frequency response, more parameter controls, more programs, and a remote control port -- all in the same striking sci-fi package.The EMT digital reverbs were something else. They were Manhattan projects, the result of intense efforts in a short period of time. Despite their high costs they were very successful, and remain one of the few digital technologies that stand the test of time, for one simple reason the sound.
Though just a few hundred of these old girls were produced, it seems a safe bet that most units are still floating around -- who would throw out such an amazing looking machine? But as 250s and 251s pass the three decade mark, the attrition rate has caught up. Power supply problems, failed capacitors, aging ribbon cables, sluggish fans, dying RAM chips...those R2D2's can develop a lot of problems. Fortunately, they are all fixable and repair is well worthwhile.
Getting set up to service EMTs wasnt easy. They have about 500 ICs, and on the main digital boards all the part numbers were sanded off in manufacturing. The 250 and 251 manuals include the power supply, converter, and analog schematics, the complex digital circuits were always kept under wraps by EMT and Gotham, the U.S. distributor. But by jumping through hoops some years ago we managed to acquire complete documentation for these units, and have tracked down all the RAM, shift register, and other obsolete IC's. Since 1990 a steady stream of 250s and 251s have shown up and we've successfully brought them all back to life.
There was just one little problem... On 251s, those custom LCD display became an Achilles heel. Near all have failed over the years, some quite dramatically. In Germany, Barco (who bought EMT in 1989) had no spares, but one of the engineers kindly gave us the original specs for the display, which mentioned that were made by Crystaloid Technologies in Hudson, Ohio. I contacted Crystaloid, told them the story, and a sales person got back to me quickly. Amazingly, they still had the original EMT specs on file and before I knew it, I was holding a price quote for a brand new batch of displays. Perfect, right?
Well, no. Crystaloid Technologies sent me another fax just a few weeks later. Victims of a changing economy, they wrote, a decision had been made that they'd soon be suspending operations, and closing entirely. They were very sorry but no new orders could be accepted
Electronic component manufacturing in the U.S. was losing ground to the Pacific Rim. Most small LCD displays like this one now came from China, Korea, and Taiwan. I Googled a dozen or so Asian firms, then sent them specs and RFQs, but with no success. Crystaloid still had the old dies and materials on hand, but the new guys in Asia were making better newer displays that werent compatible, or even close, to the original part. A newer display could be adapted, but a relatively complex PCB would be have to be retrofitted inside the housing. Sadly, the small number of displays I wanted couldn't justify the R&D time and start up costs.
The EMT 251 Color Display was born-- Fast forward to 2009 and enter Doug Jane, EE extraordinaire. An extremely talented audio designer in New Zealand, Doug had been collaborating and exchanging tips with me for many years. He serviced AMS and Eventide gear, and possessed a deep understanding of analog and digital circuit design. In early 2009, Doug told me that he had an EMT 251 with a dead display, and he was considering a retrofit solution. It had been years since I'd abandoned the project the disease had progressed and by now, nearly every 251 out there had a dead or dying display. Doug plunged into the project and the next thing I knew, sent photos of the first completed unit. He had incorporated two big improvements the display was now color, and resolution was much higher. The echo bars are displayed in different colors, making screen images easier to recognize at a glance. As a bonus, you could upload your own image for the background screen. the unit works with the original EMT 251 software and the revised software with the additional 250 reverb program.
Installation is fairly simple and can be done by anyone with with basic tech skills, the illustrated 10 page manual gives clear, step by step instructions. You take off the top assembly, remove the old display, and unsolder two wires. The PCB is removed and the new PCB and display are installed, using a cable adapter. Now four DIP switches are set three select the display timeout mode and the fourth selects 250 or non 250 software. The top assembly is reinstalled, and you're done!
If you're an 251 owner in Southern California and you'd rather that we do the upgrade, it's not a problem. The install, including a general check out and calibration, is about $275. For more information, please contact us.
We're very glad that we can finally offer this solution to EMT 251 owners.
Frequently Asked Questions -- EMT 250/251/252
You guys sell a 251 upgrade kit that adds the 250 reverb program. If I install it, will my unit really sound like a 250?
I have an EMT 252. Can you update it with the 250 program?
My 250/251 has problems and Id like to bring it in for service. How much does repair usually cost?
I live outside of southern California Can I ship my 250/251 to you for repair?
You mentioned servicing EMT fans. My fans are noisy and seem slow. Do you have replacements?
What about replacement switches, switch caps, and lamps? Do you have those parts?
Do any of these models have stereo inputs?
What about all the other EMT products?
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