“These reverb units are really rare. I’ve actually never seen one quite like this before. It’s truly one-of-a-kind.”

Meet Justin Weiss, the talented technician at the Vintage King Tech Shop who has been working hard on restoring a vintage EMT 252 reverb unit. Justin is an expert at restoring classic gear and getting them sounding better than ever. The EMT 252 Digital Reverb is no exception.

EMT have a long legacy of creating innovative effects units. In addition to building the world’s first plate reverb in 1975—the legendary EMT 140—the next year, the brand would go on to design the world’s first digital reverb, the EMT 250.

Known for its iconic “spaceship” controls and lush reverb sounds, the EMT 250 has been used on countless hit records, from Prince & The Revolution to Elvis Costello. In 1981, EMT would introduce the EMT 251, an upgraded version of the classic 250 with a new LCD display and some additional features. 

In 1985, EMT released the 252 Digital Reverberation System, a rack-mounted unit with a built-in remote control. The EMT 252 came equipped with two reverb programs: the original EMT 252 reverb program, which excels at short decay settings, and the EMT 252 linear reverb program, which sounds more natural at longer decays. Additionally, the EMT 252 offers chorusing, delay, echo loops, doppler reverb, and non-linear reverb programs.

The EMT 252 ships with 64 presets for musical instruments such as saxophones, stringed instruments, brass and woodwinds, solo vocalists, choirs, and background choirs, as well as a variety of rooms with different reverberation times. Additionally, the 252’s then state-of-the-art 16-bit processing allowed for smoother-sounding reverb tails.

But enough history lessons, let’s hear what Justin has to say about this restoration project:

“The real issue with these units is that they can be challenging to repair and there's no documentation for the digital processor board. Additionally, EMT etched off all of the IC part numbers, which makes repair difficult. We knew it would be risky to work on for those reasons, but this particular unit was in pretty good shape. 

Cosmetically, it looks great, but there was an issue with the remote tactile switches and the system was not saving or recalling programs. 

First, I inspected the system cards for any noticeable electronic failures and began recapping the control and DAC/ADC boards. I also cleaned up any cold solder joints and cleaned the PCBs before reinstalling. The remote was a little more work as it required complete disassembly. 

Next, the electrolytic caps were changed out, the memory battery was replaced, and I did some more cold solder joint repairs. Finally, I finished up with a heavy PCB cleaning, reseating the ICs, replacing any faulty tactile switches, and cleaning up some corrosion caused by failed caps.  

After reassembling the remote, I was able to perform dynamic tests and make sure the digital control and analog audio paths were up to spec. The EMT 252 remote comes with a joystick that allows you to pan the wet and dry effects left or right, which was rare for digital units of this era. It was very much ahead of its time.

Being a digital device from the 70s, one of the first things you’ll notice is that despite being digitally controlled, operation is not instantaneous—the technical explanation for this is a byproduct of propagation and processor polling delays. Unlike modern digital processors where the UI controls are instantaneous, when you hit a button on the remote, there’s a bit of processor delay before you may notice any changes.

As far as repairs go, there were no major issues. Everything was fairly straightforward. This thing is working like new now.”

Check out Justin Weiss' beautiful handiwork on this rare EMT 252 Digital Reverb module below. In addition to sounding like new, this slick studio centerpiece looks like it just rolled off the factory floor!

Jacob SchneiderIf you're interested in finding an EMT reverb or any other vintage gear, we're here to help! Contact a Vintage King Audio Consultant via email or by phone at 866.644.0160.