Posted on Leave a comment

EMT 250 and the birth of digital audio

EMT 251 at Sabella Studios
EMT 250

My experience with the EMT 250/251

When I started my first internship at Sabella Studios, the place was littered with strange things I’d never seen before. But nothing looked as strange as this black and red box that looked more like a spaceship control panel than recording equipment. That box was our EMT 251 that had been sitting in the corner of the control room and had built up an impressive collection of dust. We’re a small studio with a lot of vintage equipment, so it’s not uncommon for a piece of gear to be temporarily out of service, but this was different. No one was sure if we’d get this thing ever to work again. We could send it out to the one specialist in California who knew how to fix it, but it would cost us $1,500 just to have it looked at. As a small studio, we pride ourselves on doing just about everything in house, including the maintenance and repairs for all of our equipment. It’s how we’ve been able to survive for so long.

Opening the front of the unit to see hundreds of ICs doesn’t make the task of repairing it seem any easier. To make things even more difficult, EMT, the manufacturer of the box, scratched off any identifying part numbers to keep the ingredients of their mystical digital reverb a secret. Help came from an unsuspecting place: an intern led us to his father, an electronic technician, who was originally from Russia and didn’t speak any English. Fast forward a week or two, and he was at the studio with his oscilloscope, trying to figure out what was wrong with our 251. He decided to take it home to look at it further, and within a week, we had it back up and running.

It’s hard to imagine that the first version of any digital technology could be the best. It’s easy to see why earlier analog gear sounds better as there were better manufacturing techniques, lower cost of goods, and easier availability of materials which contributed to better overall build quality. In today’s digital world, everything eventually has a newer, bigger (or smaller), better, and more powerful upgraded model. The first version is never the best. How is it that the sound of the first digital reverb unit can still surpass even the most complex and expensive modern units?

I didn’t know, but I needed to find out…

Digital Audio

Digital audio is something everyone uses, from the home recording hobbyist to the professional recording studio. Recording digitally is built into the standard workflow when creating every genre of music. There was a time when nothing was digital, so how did the world go from entirely analog to just about completely digital? In modern music production, you don’t need to use any analog audio processing at all if you don’t want to.

The original reason people started to explore digital audio was for one reason: time based effects. Early in the history of recorded music, there was never an easy way to make delays and reverbs, except with expensive and large tools like reverb chambers, plates, and magnetic tape machines. There was a very limited amount of flexibility when it came to time based effects, which had become paramount to every single song on the radio since 1947 when Bill Putnam decided to put a speaker and microphone in his studio’s bathroom. Nowadays, we fire up whatever plugin we want, but before digital audio, you had to run it through a piece of hardware or mic in a physical space. Now how does it go from microphones in bathrooms to recording 48 tracks simultaneously into your laptop with a different digital effect on every track?

The EMT 250 was essentially one of the first plugins. It’s like if a Waves or Slate plugin you just bought came with a computer, interface, and converters and was all built into one box with the sole purpose of running that plugin, and with a $20k price tag, it certainly wasn’t cheap.

Dr. Barry Blesser

A Conversation with Dr. Barry Blesser

I had the pleasure of speaking with Dr. Barry Blesser, who is considered one of the grandfathers of digital audio. In 1974, Dr. Blesser oversaw the creation of the algorithm, and some of the hardware, for the first ever digital reverb unit.

Dr. Blesser was kind enough to speak with me and explain the history of digital audio and his involvement. He began the interview by telling me about Manfred R. Schroeder, a German physicist who worked at Bell Labs during the 1950s. Schroeder was the very first person to attempt digital signal processing. During this time, computer technology was so slow that digital was completely impractical. Processing a 3 minute piece of audio could take 24 hours. Although Schroeder’s experiments at this time were not of any practical use and were done completely out of curiosity and proof of concept, it did show that digital audio was possible.

Dr. Blesser then spoke of a chance encounter with Francis F. Lee, who would become the founder of Lexicon. “I was working in the MIT Labs at 3 in the morning because that was when I could get access to the minicomputers, and Frances Lee walked in. He was in the computer world; he didn’t know about anything digital audio. And I was in the [analog] audio world, so we bumped into each other at 3 in the morning and started brainstorming about how to merge these two. That’s how Frances Lee got started with Lexicon.”

Vintage ad for a later model of the Delta T-101

The result of this encounter was the first ever digital signal processor, the Delta T-101, released in 1971. Lee had been working on a digital heart monitor and, from Dr. Blesser’s suggestion, experimented with running audio through it. After a lot of experimentation, the result was a 100 ms audio delay line which could be used to help overcome live sound propagation delays or used as a pre-delay for plate reverbs. You put audio in, and 100ms later, it comes out. That was it. It was revolutionary at the time, but by today’s standards seems like just a step above useless. Steve Temmer, owner of Gotham Audio, commissioned Lexicon to make 50 units that he could release under the Gotham Audio name. A second version the T-102, was eventually released under the Lexicon name with an improved signal to noise ratio.

Throughout the 1960s, Dr. Blesser worked with EMT on many of their analog audio products. “They rejected the idea of doing real digital audio until Francis Lee started Lexicon. After Lexicon was successful with the T-101 they got pissed, and they said, ‘ok, we want to be in that business.’”

Peter Bermes, an industrial designer working for EMT, recalls the initial meeting to plan and brainstorm the EMT 250 involved nine people seated at a roundtable. The meeting, which went on to be the catalyst for the first reverb, Bermes says, took only 4 hours. The meeting occurred in 1974 at the EMT plant in Kippenheim, Germany. Among the group were Erich Vogl, Karl Bäder, Barry Blesser, and Peter Bermes. Dr. Blesser, along with a team of engineers, went to work on developing an algorithm they could use for practical digital reverberation. Only having the 100 ms delay box and Manfred Schroeder’s experiments, Dr. Blesser’s team built a simulator that could be programmed to run different reverb algorithms for testing purposes. After about two years of research and development, the EMT 250 was ready, and 250 units were produced.

So that doesn’t explain why the reverb still holds up in today’s world of endless digital options and newer upgraded algorithms, and more advanced convolution technology. It comes down to the sound. It just sounds good. Forget all of the pioneering and innovation that took place to develop this device. Even if this unit was introduced tomorrow instead of in 1976, it would still hold up as being a great sounding reverb, and that’s just a testament to the designers. Most of all, they made sure it sounded good.

Luckily, you don’t have to spend $20k to get the amazing sound of a 250 anymore. Universal Audio had Dr. Blesser reverse engineer the whole algorithm so they could model it in their 250 plugin. Although Dr. Blesser said that he did not hear it for himself, he was told it was completely bit accurate.

Related articles:
Can you tell the difference between real and fake plate reverb?
5 mixing mistakes that I used to make… and how to avoid them
Things I wish I learned sooner about audio engineering
The story of the man behind the RCA 44 and 77 ribbon microphones

Posted on Leave a comment

What’s more important microphones or preamps?

What’s more important microphones or preamps?
Sennheiser MD 421
“A good preamp can make a bad mic sound good, but a bad preamp can make a good mic sound bad.”

What do you buy first, a good mic or a good preamp? If you’re a new engineer looking to start building your studio, this is a question you’ve likely struggled with. If you’re a more experienced engineer and you haven’t asked this question yourself, you’ve probably heard it asked on one of the many audio message boards, forums, or Facebook groups.

The overwhelming consensus seems to be that purchasing a good microphone is a better idea than sinking your money into a preamp. This seems to make the most logical sense, especially to an inexperienced engineer. The microphone is the one capturing the actual sound waves, and it has to be the most important! The preamp is only adding volume. How much can that really improve the sound?

Your budget is a huge factor in the answer that I would give you. Though I believe the preamp is the more important stage of the signal path, a microphone may be the better choice for someone with a smaller budget. You can improve the sound more, with a more modest investment in a microphone, than you can in a preamp.

A cheap Radio Shack mic through a cheap preamp is going to sound significantly worse than a Shure SM58 through that same cheap preamp. You only had to spend $100 to gain a significantly better sound. Now let’s go back to just having the Radio Shack mic. Say you decide to buy an 800 dollar Neve clone preamp. You spent $800, yet I’d bet that the SM58 through the cheap preamp sounds better than the Radio Shack mic does through the $800 Neve clone. It’s going to take a lot more money to make that Radio Shack mic sound good with a preamp than it would by just purchasing a new microphone. But the Radio Shack mic, through a $4,000 vintage Neve 1073, might sound pretty cool. The price tag is just a tad bit out of most of our budgets.

To put it simply,

A good preamp can make a bad mic sound good, but a bad preamp can make a good mic sound bad.

Does that mean I’d rather record with a Radio Shack mic and a 1073 over an u87 and Presonus preamp? No, not at all. But it does mean that I give higher importance and priority to the preamp than I would the microphone.

I think we all agree, like with everything in audio, different scenarios call for different answers. But generally speaking, If I could only have a really good mic or a really good preamp but not both, I’d take the preamp.

Related articles:
The story of the man behind the RCA 44 and 77 ribbon microphones
5 mixing mistakes that I used to make… and how to avoid them
The “your mixes sound bad in the car” phenomenon
Things I wish I learned sooner about audio engineering

Posted on Leave a comment

The story of the man behind the RCA 44 and 77 ribbon microphones

Frank Sinatra and an RCA 44 Ribbon Microphone

Disclosure: Audio Hertz is supported by its audience. When you purchase through links on our site, we may earn an affiliate commission.

Harry F. Olson is most likely an unfamiliar name, but I’m sure you’ve heard of one of the 100 plus inventions Olson has patented. His patents include the cardioid microphone, sound absorbers, and the first programmable music synthesizer. He was directly responsible for the RCA 44 and RCA 77 ribbon microphones. In the early twentieth century, there was a surge in innovation and technology, and Harry was at the forefront, exemplifying the ingenious spirit that embodied the people of the time. Olson spent 40 years working with RCA, where he was in charge of their acoustic research department and many of the great inventions that came out of it.

You can’t mention ribbon microphones without mentioning RCA, and you shouldn’t mention RCA without mentioning Harry Olson. Ribbon microphones were the last of the four main microphone designs invented. These microphones quickly grew in popularity and eventually into legendary status for their smooth, warm, and natural sound. RCA used their resources to provide an extensive research and development effort that was unrivaled by any other company at that time.

Who is Harry Olson?Harry F. Olson

For over 40 years, Harry Olson worked for RCA innovating and developing new products, mainly for their acoustical research department. Born in Mount Pleasant, Iowa, in 1901, Harry was technically inclined from an early age and showed a strong interest in science and technology. His parents catered to his scientific spirit and built him his own laboratory;  he spent time there making things like a steam engine and wood fired boiler. After graduating at the top of his class from the University of Iowa’s College of Engineering, he received a scholarship to attend graduate school and earned his Master’s Degree in acoustics.

After graduate school, Harry moved to New Jersey and joined RCA’s Research Department, and it was there that he worked on the wide range of products for which he became most famous. During World War II, just about all American companies switched their focus to military technology, and RCA was no different. Olson led a group that worked on military projects with a strong emphasis on underwater sound and antisubmarine warfare. This work included improving sonar transducers and voice communication transducers that could be used in noisy environments.

When the war ended, Olson went back to working on his research in sound reproduction. He famously conducted an experiment that would determine the preferred bandwidth for reproduced music. Before this experiment, studies had shown that listeners preferred a high frequency cutoff of 5 kHz. Olson didn’t believe this to be true. He was sure that if the sound was free of the imperfections that were common of the time, such as added noise, hiss, and harmonic distortion, then the listeners would prefer full frequency sound reproduction.

To test his hypothesis, he set up an orchestra with the listeners positioned in a way that a physical acoustic screen with a low pass filter could be opened or closed. This experiment proved his theories to be correct– the majority of the audience vastly preferred full frequency reproduction. It was because of this experiment that high fidelity sound equipment gained increased popularity. This ultimately impacted everything from record players to amplifiers, speakers, and tape recorders.

Ribbon microphones

The first commercially produced ribbon microphone (also known as a velocity microphone) was released in the early 1930s. A ribbon mic works like a dynamic mic, except instead of using a moving coil as the transducer, it uses a ribbon. The ribbon picks up sound much like the way your ears do naturally. This is because ribbons are designed similarly to the way your ears pick up sound. Most ribbon microphones are open on both sides, which naturally gives them a figure-8 polar pattern. Interestingly, this made them very popular with the film industry as they could place the camera in the null area of the microphone and minimize the amount of camera noise bleeding through.

The RCA 44 and 77

Without a doubt, the two most famous ribbon microphones are the RCA 44 and 77. Both were invented and patented by Harry Olson. The 77 microphone was the very first ribbon microphone designed and introduced by RCA. It was rumored to have been in development as early as 1929 but wasn’t officially announced until 1932. The first 77 model was the rarest of all RCA microphones and featured two ribbons and an “acoustic labyrinth,” which allowed it to be uni-directional.

The 44A was a smaller and lower priced version of the 77A. The lower price point was a significant contributing factor to this microphone’s success and popularity. This is the microphone you think of when you picture Elvis or Frank Sinatra or an old radio broadcaster. The look of the microphone might even be more legendary than the actual performance. The 44B and 44BX were both slightly larger versions of the 44A. The BX has the ribbon mounted further toward the back, giving it a smaller figure 8 pickup pattern on the rear side.

The BBC noticed the 44 being used in American broadcasting and wanted one for themselves. The only problem was it would cost them £130 ($8500 in 2017). This was way out of the BBC’s budget, so they decided to make their own ribbon microphone. F W Alexander, who worked in the BBC research department, invented the Type A, whose successor, the 4038 is still being made by Coles Electroacoustics.

Coles 4038
Coles 4038


Ribbon microphones today

Today, ribbon microphones vary in price. Modern technology has made it so the manufacturing cost is low enough to make entry level ribbon microphones possible.  There are also companies like AEA based out of Pasadena, CA, that work tirelessly to make the most accurate reproductions of the classics. One of their newer ribbon microphone designs is the R88 which is a stereo microphone that looks like a huge RCA 77 and sounds breathtaking. You can hear it being used to mic an entire band on the YouTube channel “One Mic.”

The RCA 44 was discontinued in 1957, yet they are still seen in studios all across the world and are still going for thousands of dollars on eBay and Harry Olson’s impressive legacy has left us with these indispensable tools that have dramatically and significantly impacted the history of audio.

Related articles:
What are the different types of compressors?
The “your mixes sound bad in the car” phenomenon
Things I wish I learned sooner about audio engineering
[Even more] Things I wish I learned sooner about audio engineering

Posted on Leave a comment

How two guys in New Jersey created the most desirable equalizer: Pultec EQP-1A

The most desirable equalizer Pultec EQP-1A

Pultec is the holy grail when it comes to equalizers. But, the reason why Pultec is so great can seem elusive if you asked someone why their answer would be solely their opinion. You could attribute their success to the transformers, the tubes, the Q curves, or being a byproduct of the times, the place, or the people. But really, it was all those things that created the perfect storm for genius. The fact that it’s still one of, if not the most, sought after audio equalizers ever made is an even further testament to that.

Pultecs will always hold a special place in my heart. If I had to list the most important things to me, it would go, my family, Pultec EQP-1A equalizers, and then my girlfriend… Okay… Maybe it’s not that extreme, but I do love the things. I started interning at Sabella Studios in Long Island, New York, in my sophomore year of college. The first time I walked in, I immediately noticed the rack of 9 foreign looking blue boxes taking up the whole wall. I’d never heard of a Pultec, I’d never even seen an equalizer that looked like that, and I certainly didn’t know what made them or the fact that there was a whole wall of them so special. The more I got to use them, the more I grew to love them and started to understand what a privilege it was just to use even one, let alone a wall of 9 of them.

If you took a trip to Teaneck, New Jersey, in 1955, you just might run into Gene Shenk and his longtime friend, Ollie Summerlin, tweaking what would become one of the first Pultec EQP-1 equalizers. Gene and Ollie… they were Pultec. The whole operation was never more than three people, and the majority of the time, they were responsible for everything, including engineering, designing, marketing, and producing each and every piece of gear by hand. These two guys in New Jersey left their mark on the recording industry forever, and not many people even know their names. You can’t go into a recording studio without seeing an original Pultec or a clone of an original, or a plugin emulating one.

Ollie and Gene met studying electronics at the RCA Institute (now the Technical Career Institute College of Technology) in NYC. After school, Gene spent 14 years working for RCA while Ollie enlisted in the Navy. After WW2, Ollie ended up at Capitol Records as an engineer and sold Ampex tape machines before meeting with Shenk to form Pulse Techniques. Pulse Techniques was the formal name for the company that produced the Pultec EQP-1A.

Starting in 1953, the two man team of Ollie and Gene made every single item to order by hand. When people say, “they just don’t make them like they used to…,” they are right. They don’t make them like they used to. You couldn’t make an equalizer today with the same components as an original. Even if you did have an unlimited amount of money, some components are no longer available. Many people claim the transformers on the input and output are the reason for much of the magical powers of the unit. This point is emphasized when you just run audio through the unit in bypass. You can hear the difference even with no EQ engaged.

Listen to these samples — the first is a dry vocal track with no Pultec, and the second is the same vocal track that is being run through a Pultec but with the bypass engaged.

Dry Vocal

Bypassed Pultec Vocal

The company first made variable filament supplies for tubes and stepped oscillators. In 1956, the first version of their equalizer, the EQP-1, was seen in the Pultec catalog. They were advertised to the broadcast industry, and the main unique feature and selling point was the tube makeup gain which allowed it to be engaged without the signal dropping in level.

In 1961, the EQP-1 was replaced by the updated EQP-1A, which had added frequency selections. The new 1A model had added a 20 Hz boost and attenuation, a 16 kHz boost, and a 5, 10, and 20 kHz attenuation. In 1981, Shenk was finally ready to retire. He tried, unsuccessfully, to sell the company and eventually ceased production and shut the doors for good.

A common myth is that the Pultec passive circuit designs were licensed from Western Electric. This is not true. The manual states, “licensed under patents of the Western Electric Company,” but that is only for the use of negative feedback and has nothing to do with any of the actual circuit designs.

After closing down in 1981, Gene Shenk received a call from NYC Power Station owner Tony Bongiovi. Bongiovi wanted to place an order so large that Gene couldn’t say no. Eventually, 24 units, mainly the smaller 2U rack version of the 1A, the EQP1A3, were produced for the last ever production run made by Gene Shenk.

Nile Rogers Pultecs
Nile Rodgers sitting in front of the racks of 24 Pultec EQP-1A3s in Power Station’s Studio C

Interestingly, the Q curves on a Pultec are so broad that adjusting 30 Hz can affect frequencies up to 1kHz. Also, the manual explicitly states, “do not attempt to boost and attenuate simultaneously on the low frequencies,” yet this is the very thing for which this EQ is famous. Boosting and cutting simultaneously may seem counterproductive, but doing so makes the curve dip before the boost starts, which results in what can only be described as magic.

In the early 2000s, electrical engineer Steve Jackson decided to try and recreate Pultec with some guidance from Gene Shenk himself. Jackson secured the rights to the name and started producing EQP-1A3 again. Many others have tried to copy, clone, and emulate the Pultec EQP-1A. Many will argue that some do it quite well. Still, to most that have had the pleasure of using the original units, there’s an undeniable magic that just can’t seem to be captured in an algorithm or with modern components and manufacturing techniques.

Related articles:
EMT 250 and the birth of digital audio
5 mixing mistakes that I used to make… and how to avoid them
Things I wish I learned sooner about audio engineering
The story of the man behind the RCA 44 and 77 ribbon microphones

Posted on Leave a comment

The best designed and most enjoyable effects unit ever: Eventide H3000 UltraHarmonizer

Letter Brian Eno wrote to Eventide in 1992

When one of the most influential and well regarded electronic musicians praises your effects unit as the best, it should hold some weight. Not only did Brian Eno love his Eventide H3000, but he loved it so much that he actually took the time to write to Eventide to congratulate them on designing it.

Eventide started in the basement of the Sound Exchange, a recording studio located in midtown Manhattan. Their control room wasn’t big enough to fit a tape op, so studio owner Steven Katz commissioned Richard Factor to create a device that would allow him to locate the tape to a specific time. Eventide was born.

In 1974 they developed the H910 Harmonizer, one of their most notable products, which was the first digital pitch shifting device.  From the H910, the H3000 would be born. Interestingly enough, the H910 Harmonizer was first used to speed up the dialog of older sitcoms, like I Love Lucy, without changing the pitch of the voice.

In 1986, Eventide released the H3000. But what makes it so special? Before this unit, if you wanted to speed up time, you also had to speed up the pitch. This one significant advancement inevitably leads to tools that are paramount to modern recordings, like Auto Tune, Melodyne, time stretching, etc.  I think to truly grasp the full magnitude, you have to consider the period during which it was released. Up until that time, every effect that anyone ever heard was produced through hardware. There were no plugins. The majority of the time, there was one piece of hardware that did one specific effect.

If you could design the most perfectly laid out effects unit with what seems like unlimited capabilities, the H3000 would be it. With only 7 buttons, a jog wheel, and a number pad, finding and altering your favorite presets is quick and easy for even the most novice engineer. The H3000 could not have been better received, and it wasn’t long before every studio had an H3000 in their rack. The H3000 was the first unit to offer true diatonic shifting or shifting that stays in key, but other features include*:

  • Dual Shift –  Two separate pitch shifters
  • Layered Shift – Two pitch shifts from one input
  • Stereo Shift – Mono-compatible stereo pitch shifting (maintains stereo imaging)
  • Reverse Shift – Backwards-talking pitch shift
  • Swept Combs – Six sweepable delay lines with stereo panning
  • Swept Revere – A dense reverb with smooth sweep capability
  • Reverb Factory – A full-featured reverb with EQ and flexible gating
  • Ultra-Tap – Twelve delay taps with full control over panning, level, and delay, Includes a diffuser to generate dense gated reverb effects.
  • Dual Digiplex – A stereo delay with smooth delay change
  • Long Digiplex – A 1.5 second delay with smooth delay control
  • Patch Factory  – A “modular” effects program that lets you design your own effect. “Patch” together delay lines, filters, and pitch shifting to create never-heard-before effects.
  • Stutter – Get that sound – effortlessly
  • Dense Room – Our densest reverb, with unique front/back position control
  • Vocoder – This is our version of the classic vocoding effect
  • Multi-Shift – Two six-octave pitch shifters, two delays, panning, and patchable feedback paths make this program incredibly useful.
  • Band Delay  – A multi-tap delay line feeding eight resonant bandpass filters makes for some sounds like you’ve never heard.
  • String Modeller – This program lets the H3000 double as an extra voice in your MIDI rack
  • Phaser – A wonderfirlly thick, smooth, phase-shifting effect that is hard to beat

*List source: Vintage Digital

It’s over 30 years after the release, but the H3000 is still found in countless studios across the world. Through all the changes in technology, the unit and its effects not only hold up, but many would argue still surpass anything made in the modern era.

Eventide has given engineers a cheaper option– they released the H3000 plug-in for $350. I can’t vouch for how good it sounds or how it compares with the real unit, but you can download the demo here and try it for yourself.

Below are samples I’ve recorded of vocals going through our H3000:

Dry (no H3000)

Dual Shift

Stereo Shift


Pitch Quantize


Big Vocal Plate

Tight Room

Related articles:
Things I wish I learned sooner about audio engineering
[Even more] Things I wish I learned sooner about audio engineering
EMT 250 and the birth of digital audio
The “your mixes sound bad in the car”