The CEDAR Story with Andy Walter and Simon Gibson

The CEDAR Story with Andy Walter and Simon Gibson

We sat down with Abbey Road mastering engineers Andy Walter and Simon Gibson to find out more about our history with CEDAR Audio, world leaders in audio restoration and noise suppression.

Back in the late-1980s, we were one of the very first to experiment with a genius new technology created by the Signal Processing Laboratory at Cambridge University. Since then, CEDAR has been utilised on countless disc transfers and continues to be used every day for Online Mastering projects.

Read the full CEDAR Story below.

Andy Walter

When I started here, Cambridge University were using Abbey Road as a test centre for a research project. This developed into what is now a worldwide company called CEDAR – which stands for Computer Enhanced Digital Audio Restoration. They developed a system that could be used to take out clicks and crackles on records and because we were doing a lot of record transfers at the time, we were interested in that. So, Abbey Road bought the system and lo and behold I was the engineer that sat down with it and started using it in the first few years. No one else at that time had this technology and it was incredible.

The way it would work is I would record lots of records during the day and load them into the computer. You would put in various clever codes and leave it to ‘cook’ overnight. I worked closely with designer Dave Betts who would always have the right codes to get great results. He would say, “Try writing in IE7, that sometimes works…” and it often did! It was quite labour-intensive and took a long time, but you know, the company started getting better and better with updates all the time.

Now with v13 you can run a transfer straight through and with only about a sixteenth of a second delay, it removes clicks, vinyl crackle and any underlying noise without damaging the music. I was doing it recently with an INXS interview that was on vinyl – you wouldn’t know it came from vinyl now! It’s like restoring an old oil painting where you take all the dust and grime off and you’re left with all these colours you never knew were there.

It’s not an on/off thing though, you can be very damaging. It can totally ruin recordings if you over-process it. If I took out all the noise form a record from 1929, it would sound muted and dull because recording technology at that time was very limited in its frequency response in the top end. As the recording gets later and you get into LP recordings, there’s more frequencies captured so you can have more success taking more noise out.

We also use EQ sometimes along with it, to artificially boost the problem sounds on the record so the computer can process it more effectively.

Having come from the basis of cleaning up old records, now this kind of equipment is used all the time on newer recordings. Simon and I spent years going through every single track of The Beatles recordings and cleaning things up.

Throughout the years I would often give them feedback and once I said, “We need to be able to see each section of the audio on the screen and be able to open them up and process them individually”. What they did with that was create the CEDAR Retouch plugin which is just fantastic. I use it all day every day for normal mastering jobs.

When I did the film score for the first two Harry Potter films, we had a Timpani note that should’ve played and I used Retouch to add it in from the next bar. It’s like Photoshop for music.

Simon Gibson

I started in 1990 and Andy started in 1991. Fairly soon after he arrived, he came up to Room 13 which for many years had been the 78 transfer room. At that time, they had the earliest CEDAR system in there and he began working with it. CEDAR were the first in the world to develop digital tools to clean up disc noise (surface noise, tape hiss, etc.).

In the early-to-mid 1990s I was working in the room downstairs, which was next to Studio One, a sort of tape remastering room. Andy and I brought the CEDAR system down there and that was my first interaction with it. Compared to what had been possible before it was a quantum leap really. Before, they would transfer 78s to analogue tape, then transfer to vinyl. Occasionally they would take a pair of scissors to the tape where there was a particularly bad click and snip it out. That was destructive editing because you’d actually be removing a bit of time.

CEDAR’s non-destructive technology came at a particularly good time as the CD was also hitting its peak, there was suddenly a possibility for the record companies to not only reproduce the vinyl back catalogue but also the 78 back catalogue in a way not possible before. Over the years CEDAR have been quite forensic in the way they’ve developed the different programs within their toolkit to address specific noise issues, whether that be broadband tape hiss and clicks or digital issues like clipping.

They have a standalone package called Cambridge and there are a bunch of different programs you can use within it. Cambridge runs on a separate PC which has its own digital in and out. It also has a hard drive so you can load audio to it and batch process or, as we most often do, use it as a black box by sending audio in from our main workstation, processing it in real time and capturing the result coming back out.

If it’s a disc, generally we’ll be using what we call the “De-clickle” which is a combined de-click and de-crackle program, adjusting the parameters of that and finding the ideal threshold.

There’s a DNS software version on here which originated as a physical box for use on TV and film locations where there’s often a lot of extraneous noise. It’s a really clever tool. Different from the NR-5, which basically takes a fingerprint. For example, if you’ve got a bit of blank tape at the front without music, you can use a few seconds as a sample to remove it from the rest. You can be very very subtle with it, you only need to take a few dB off the higher end to make a perceptible difference in what you’re hearing.

The real go-to tool is CEDAR Retouch. When it was launched 20 years ago it was an absolute shockwave for audio engineers. You could now do something that was absolutely impossible before. It allowed you to select a small bit of audio, pull it up in a spectrogram window and deal with the click, hiss or sound you want to remove. It’s a non-destructive thing, it just looks left and right at the clean audio and replaces the selected area. That’s what led to the forensic nature of projects like The Beatles remasters. On vinyl you’d never hear those things, but when it was done for CD we made the decision, “well actually, those sounds were introduced by the technology, it wasn’t heard in the studio, it’s not part of the song, so take it out”.

I still use Retouch every day on Online Mastering jobs. If I hear any electrical clicks, I can just pull it up on Retouch and in seconds, gone. It’s great with bass frequencies, like if there’s a plosive sound on a vocal mic. With pitched noises or whistles that have harmonics, you can home in on those and take them right out. A very powerful, versatile piece of kit.

All these tools have been an important part of our armoury for 30-odd years.

CEDAR Retouch on The Beatles 2009 remasters

Drop out on Day Tripper BEFORE

Drop out on Day Tripper AFTER

Low-end pop BEFORE

Low-end pop AFTER



Distortion BEFORE

Distortion AFTER


Gordon Reid, MD of CEDAR Audio Ltd.

The history of EMI and CEDAR goes back to 1988 when – even before the CEDAR name had been coined – the Signal Processing Laboratory at Cambridge University provided to EMI a non-real-time system based upon its initial research into audio restoration. Two years later, I began discussions with Chris Buchanan (Manager of Transfer Operations) at Abbey Road regarding the installation of the newly released CEDAR Production System and, in December 1991, the studios purchased CEDAR System serial no. 000017.

The company established an excellent relationship with Abbey Road. New modules for the system were appearing at great speed, and the studios upgraded through various revisions of the CEDAR Production System, then to CEDAR for Windows, and then to CEDAR Cambridge, version 14 of which (released earlier this year) is still in day-today use at the studios.

In 2002, Simon Gibson and Andrew Walter were present when CEDAR unveiled spectral editing, initially on the SADiE system and later on its own CEDAR Cambridge platform. CEDAR Retouch™ became a go-to tool at the studios, perhaps used most notably on The Beatles remasters and the release of the Beatles Rock Band game in 2009. Later that year, Simon and I co-presented a lecture on Audio restoration at Abbey Road Studios and the role of CEDAR Retouch to the Institute of Broadcast Sound and, in 2010, to the Royal Academy of Engineering.

CEDAR is proud of its relationship with Abbey Road Studios, which has now existed for more than three decades. I think that it's fair to say that we value the studios as much (or perhaps even more) as a friend than as a customer, and we always look forward to our visits and to meeting Simon, Andy and their colleagues at industry events.

Related News