Portrait CS Mastering

Christoph Stickel is a mastering- and sound engineer. He has been working in this profession since 1992 and has been based in Vienna with his studio "CS Mastering" since 2016. Before that, he worked at the renowned msm studios in Munich, among others. With his specialist knowledge and many years of experience, he creates productions that meet the highest quality standards. He is known in professional circles for his excellent work and enjoys an outstanding reputation.

Mastering is the final step in the production of sound storage medium before they are released on the market. Christoph produces around 250 masters per year for vinyl, streaming, CD or tapes. To date, he has produced a total of around 5,000 masters. With the album "John Williams: Violin Concerto No.2, Anne-Sophie Mutter, Boston Symphony Orchestra" on the “Deutsche Grammophon” label, he is nominated for the 65th Grammy in 2023 as "Best Engineered Album, Classical".

He works for labels including Universal Music, Sony Music, Warner Music, Act Music and ECM. He has mastered recordings by Martha Argerich, Leonard Bernstein, Chick Corea, Jack DeJohnette, Wilhelm Furtwängler, Friedrich Gulda, Charlie Haden, Keith Jarrett, Manu Katché, Gidon Kremer, John McLaughlin, Zubin Metha, Pat Metheny, Kent Nagano, Oscar Peterson, Simon Rattle, Michael Schenker, John Scofield, Yello, the Berlin Philharmonic Orchestra, the Munich Philharmonic Orchestra and the Vienna Philharmonic Orchestra, among others.

He gives lectures and postgraduate courses at the “Erich Thienhaus Institute” in Detmold (Germany) and at the Vienna “University of Music” (Austria).

During my visit to Vienna in June 2023, I was able to conduct an interview with Christoph Stickel on the restoration of historical tape recordings.

[The comments in square brackets are by the author]

Claus: You receive tapes from different decades for restoration. How do you go about unpacking the tapes and how do you examine the material?

Christoph: When I receive a tape in a box, I have absolutely no idea what to expect. Opening the box is a very critical moment because many tapes are not on reels, but on a bobby [metal reel core with free winding, "pancake"]. Many tapes are good, everything works, but it happens more often (approx. 5%) that the bobby no longer has a connection to the tape. If I were to cheerfully open such a box, it could all fly out at me. Then I'd be busy for a day getting everything back together again. So, no matter how good or bad the material is, I always carefully slide a winding plate underneath to see if it fits mechanically. Can I wind the tape? Or do I have to wind some of it by hand, which takes me a hour. If the tape can be wound, this is done slowly. I sit next to it to see: Is the material sticking or not sticking, what do I have to do? Will the splices hold or will the material fly around my ears? I always have my hand on the stop button so that I can stop the machine immediately. If an adhesive spot tears, I have to remove the adhesive and put on a new sticker. Once I have rewound it, I can assume that it will stay in this good condition.

With very old tape material, there are not that many differences between the various manufacturers. The tape material becomes interesting at the end of the 1970s and beginning of the 1980s because it has become softer and softer in order to wrap around the sound heads better. There are tapes from certain eras that are full of moisture. They stick and smear (e.g. Scotch, Ampex). Here the restoration starts with the material. I may have to bake them. There are also old tapes from the 1940s, e.g. Agfa material, which I know very well from the German archives, which are hammer-like good, so I hardly have to do anything. I often put the tape on and it plays like a dream.

Claus: When does tape material have to be baked and what happens during this process?

Christoph: If I see that the material is sticking during the first playback or rewinding process, I stop immediately. Then I bake the tape according to certain rules. I bake about 5% of all tapes first. This baking is nothing more than dehydrating the tape over a very long period of time at a constant temperature. This means that the moisture in the tape is reduced and the small metal particles stick to the carrier tape again. After this process, the tape can be played back without any problems. After dehydration, the tape is therefore in the best possible condition. This condition lasts for one to two weeks. It must therefore be processed quickly.

Claus: Can a copy master or a backup copy be made as soon as the tape is playable? Or do further preparations have to be made?

Christoph: The very first thing I do when I can play the tape is to check the information supplied with it. This is important in order to be able to play it with the correct settings and parameters. Was a noise reduction system such as Dolby used, and if so, which Dolby? Or was it telcom c4? What reference level was the tape recorded at? Was the equalization CCIR or NAB? Are there measurement tones on it? It is assumed that this information is available on all master tapes. Unfortunately, this is not always the case. For many parameters, a standard is assumed, we know this, but it has not been noted or the notes are no longer available. Then you have to find out whether it was recorded in New York (USA), for example. So it is more likely to be a NAB tape than a CCIR tape. You can hear the difference between NAB and CCIR quite clearly. If you have historical material that is also available on a record, then you have a reference for orientation. If there is digitization or other publications, then you can say: The record was recorded this way or that way back then, so the tape is probably correct. If it has level tones and preferably also Dolby Noise, then you're on the safe side. Then you can calibrate your tape machine and wobble the sound heads so that the values fit exactly.

Claus: So you adjust your sound heads so that the tape can be played back in the best possible way. How far do you move away from the reference setting of the tape machine?

Christoph: Adjusting the tape machine to the tape is very important and often a very large part of the overall work. The aim is to get my machine as close as possible to the state it was in when it was used for recording. There is actually no reference setting here. Yes, there is the reference tape as a reference, but unfortunately I don't care about that at all during playback. My machine always starts from zero and I feel my way towards the respective tape. Some sound heads are then sportily wobbled. Or I come to the decision to change sound heads or other madness that comes along, such as demagnetizing the sound heads three times to minimize crackling. So a new reference is created when the azimuth and the Dolby fit exactly. This reference forms the basis of my further work. Once I have found an optimal starting position, I start making corrections. The next adjustment is made by ear, e.g. if it sounds a bit musty. Then I add 1 dB or 2 dB in the high frequency range to the playback control of the tape machine. So I change the calibration of the tape machine at this point to get the best result. This is also where the decision is made as to whether changes are made via devices that follow analog. So I first create a basis that I can work with. First of all, it's about the technical side: am I using my machine as optimally as possible with the device that was used to record the material? If I have optimized everything as best I can, then that is the zero situation, the zero point. Then I always start by making a digital backup copy so that I can develop all the considerations further from this copy. I then don't touch the tape for the time being to protect it. Further processing is done with the DAW [Digital Audio Workstation].

Claus: How do you proceed with digital music editing and how is the analog master tape created?

Christoph: I can try out a lot on the digital side. It's more luxurious. For example, if there is a small jump in level at exactly 04:30 minutes, then I have to readjust the fader or take further measures. Or further back, at 13:22 minutes, something terrible happens. The cut is such that there is a massive crash. I then have to quickly lower the fader and make a note of it. So I have the material in my DAW and can practice with it and repeat it as often as I want. This allows me to optimize my purely analog processing chain until I'm really happy with the sonic result. These settings then remain unchanged. Then I put on the original tape and go out of the tape machine via my analogue devices such as equalizers and phase shifters. Sometimes I also use compressors, but not only to narrow down the dynamics, but also to straighten out certain irregularities. I had already decided whether to work with tube compressors and tube equalizers or solid state [devices with semiconductor components]. Now the entire recording is done as a tape recording with at least two or three passes. I listen to the result via the rear band control and can now make final adjustments. For example, I may have to add a little more treble to make it sound as good as possible on the master tape. If the tape closes a little due to hysteresis, then I don't have to take out a ¼ dB at 250 Hz, for example, but ½ dB so that it sounds open and perfect as a master tape. In the end, I almost work myself to death. But then: Take fresh tape, record the final master tape so that it sounds as good as possible, and that's it.

Claus: Are there any problems with pitch fluctuations when editing the tapes?

Christoph: If a tape is faster or slower, then I have to adjust the pitch changes, i.e. the pitch. This happens with early recordings that were made with power-synchronized tape machines if the power frequency was not stable during recording. In this case, the tuning of the orchestra would be too high or too low at the correct playback speed. In the best case scenario, I can find out the exact tuning of the orchestra at the time from someone involved or have to do some other research. Then I have to set the pitch on my machine so that the tape is played back at the correct tone pitch.

Claus: With every transfer you catch some noise. Do you work with noise reduction systems?

Christoph: A tape played "hot" [at a high level] hardly has any noise and my working copy will have a maximum of 3 dB more noise. I often use Dolby SR for my master tapes. The decision to use Dolby was a terribly long consideration. It was so difficult because Dolby has eight dynamic control stages. This means that if the Dolby device doesn't work 100% in playback as well as recording due to an ageing process or something similar, this can become critical. With a properly controlled Dolby SR tape at 38 cm/s, the noise performance and dynamics are comparable to a good digital recording. In other words, we are really on the very good side here. Using Dolby SR means that I always have to discuss everything with the person for whom I'm making the tape. If it's for a vinyl cut, for example, I'm in very close communication with the cutting studio: Do you have Dolby? Which version do you work with? How do you do it exactly? When have your devices been for revision? When it comes to making tape copies, it makes sense to synchronize my Dolby SR equipment with the equipment of the tape editor, such as HORCH HOUSE, via series of measurements. Zero errors are the optimum.

We have also carried out tests with the telcom c4 noise suppression system, which worked very well. Maintenance is easier with telcom c4. I have to say, I didn't really have telcom c4 on my radar, but it works very cleanly. I found the signal coming out surprisingly good, which is great. But still, the best possible technical system is actually Dolby SR.

In terms of noise, we also carried out tests with half-inch tapes. You can simply run at an even higher level, i.e. even "hotter", which works excellently. There are also ways to reduce noise in analog. These are devices from the analog era, so-called spectral processors, with which you can reduce the noise a little in certain areas. You have to do that by ear. With all the tricks at my disposal, my master tape has to be at least identical to the tape I received in terms of the signal-to-noise ratio and, above all, the aural noise. So the absolute premise is: what comes out of my tape must not be worse at any point than what I have as source material. So if I make a change to any technical parameter and this results in a deterioration, not necessarily in terms of measurement, but also in terms of hearing, then I must not do that. I have to keep my hands off tapes that I play back and say: ok, I'm going to do something just to have done something and make them worse as a result.

Claus: I've had old tapes that had channel differences in level. I can imagine that this happens more often.

Christoph: Very important topic. There are tapes that are 3 dB to the right, for example. Straightening this out, i.e. moving it back to the center, is quite possible. I have some tapes where the first set is 6 dB louder on the right-hand side and everything is centered again from the second set onwards. This means that I have to master the first set accordingly and then make a cut on the second set and move everything back to center.

Claus: Are there any other parameters that need to be taken into consideration?

Christoph: You can split a stereo recording into the left and right channels. But you can also split it into the mono and side signal (M/S). In other words, into correlating and non-correlating parts. This can be a powerful tool for processing the mono and spatial components separately. If I split my stereo signal into the M/S signal, I have the option of making the stereo stage wider, narrower or slightly deeper, among other things. As vinyl cutting techniques have improved, I can now make the stage a little wider than was possible in the 1960s and thus draw the stage more correctly. This results in a cleaner representation that is more like the original recording. The realization: Oh, that's how it was meant to be back then! The music should not remain in the middle, but if I set it up a little differently, the room is depicted more clearly and cleanly. Suddenly an orchestra is reproduced correctly without the timpani flying around your ears in the mid-range, for example.

Claus: Can these parameters also be edited using analog technology?

Christoph: Thank God we have, I'm exaggerating, 100 years of analog technology in music recording. There are wonderful tools. Developed by people who have worked with it, who have thought about it. These ideas have also found their way into modern mastering tools. I can easily repair errors such as pops, clicks, noise and distortion digitally, but not in analog, or only to a very limited extent. I once had the situation where I was playing a tape and suddenly there was a horrible crack over a length of 30 inches. The tape was torn from top to bottom and also stretched. I sat there, wearing gloves and tried to glue the tape back together. In this area, you can hear that something is not quite clean. In digital, with a lot of work, I could get it restored. In analog, I have to have it written on the record cover: There is a mistake at minute 06:35, please ignore it.

With analog remastering, there are ways to make audible what is on the tape. In other words, not to add new highs, but to work out the highs that are there and make them sound better. That means, for example, in a piano recording, the descant [the highest pitch on certain instruments], which has a certain shape towards the top on a Steinway grand piano, for example, as played by Ms. Martha Argerich, sounding a little musty on the original tape, to say, I can raise the 8 kHz that are actually there. The piano's run was a little underemphasized and suddenly it sounds clean and can now flow as it was originally intended. Over the years that you work with it, you learn a few tricks on how to approach the signals. How do you get them cleaner, clearer, how do you get more information out of the tape. With a few devices that are perhaps unusual, that aren't everywhere, that are special and can do a lot. Digitally, I know from my own experience, you tend to use a restorer. There are various tools that you can use to restore like a hammer, e.g. if the music is a bit musty at the 15th bar, but sounds open again from the 18th bar onwards. Then I make my equalizer dynamic, create timecode points, open it upwards and close it downwards: I can't do that in analog.

Claus: How long can such a restoration take?

Christoph: Let's take the request to master the tape "AAA" [AAA: analog recording, analog mixing, analog mastering]. With the third A, I really don't know what to expect. Will I be sitting for ten hours or, at best, five hours? I put the tape on, there are metering tones, it's all on there, I measure everything, listen and say: Ok, I've found two little things, the rest is awesome. Then I'm done after five or six hours. In other cases, it takes me two to three days. I realize that the tape has to be baked for days. Then I can't do anything to it for half a week and have to start all over again. Has it worked now? Or does it have to be baked a second time? Then a deadline that would have been last Friday, for example, has long since passed. You can imagine that a lot of things never get paid because I simply say: I can't do it any other way. Unless you have a huge title, like a Karajan or a Furtwängler with a big record company behind it, as a sound engineer I often pay extra. It sometimes happens that I'm on the job for half a day before I say: Man, there's something wrong with the tape, I have to listen to all the copies. If I'm lucky, the archive will send me other versions such as backup copies, production masters, etc. Then I have umpteen tapes that all have to be set up individually on the machine. I can only evaluate each tape if I have set everything up optimally. About the versions: There is the original tape. Copies of this were once made for duplication for records, cassettes or similar. The original tape does not necessarily have to be of the best quality. It may be that a backup copy sounds better. This is the activity that takes a lot of time and effort until I get to the point where I can say: Man, the first movement sounds better from this tape and the second movement sounds better from the other. And then the question: How deep do I go into the music? Do I go movement by movement or bar by bar? Do I use the sheet music or the full score for my assessment? What do I allow myself to cut together from different versions of the same recording in order to achieve the optimum result? Then I take large sections from the backup copy, for example, which I can cut inaudibly in analog. So I compile the result from different versions. This is also a certain kind of "forensics" [laboratory analysis] that happens in analog. That makes the work very nice, because you no longer think in digital terms, where a lot is possible and feasible, but often also falsifying. You think much more over a somewhat longer period of time and find your way deep into the musical material. A typical, small, technical click, a chair creaking or things like that simply don't matter to me. I ignore it because I just think it's normal. I then listen to other things. That means I have to listen through all the tapes, digitize them in parallel, write down all the comments. A day can pass very quickly. And all that just for the assessment: Is this or the other version better, at which point is one version better? Can I even adapt the versions to each other? It has to result in something complete. In contrast, a classic that doesn't take up much working time: you listen in, call the client and say: That's not possible, the tape is broken.

Claus: Please describe a maximum situation that you went through during the restoration process?

Christoph: There are very few situations. In one case I worked "hybrid". There were irreparable defects in the first two tapes. So the first half of my later tape came from a vinyl record that had never been played before and was reproduced as well as possible. The rest comes from tape. Of course, this is all noted in the booklets. These are crazy steps to get it right. Sometimes I even call the archive again. The nice thing is, because I do a lot, I often have very good contacts there. These people are then also keen to ensure that we get the best result in the end: "Can you look again, if there's probably another version..." "That's right, Christoph, you're right, there might be something there..." I get a call two days later: "We've found something. We'll send it to you." At that moment, the whole process begins again. Transferring the tape, setting everything up, those hours of work.

Claus: Once you've worked out everything on the digital level, do you then work with your to-do list?

Christoph: I have a big list, I do everything manually, according to a timeline. I let the digital run along in the visual form on the monitor. Then I see: Ah, that's the same place as on the tape. I can see when I need to cut. I can move back and forth very quickly. It's not complicated, I can do it very well manually. But you also have to imagine: I'm not as experienced as the radio sound technicians and sound engineers of the 1970s to 1990s, whose job it was to run broadcasts day and night and only work from the tape. For me, it's often very physical work. There are sometimes three or four tape machines in the room and all the equipment is switched on. The room temperature goes up. I sit in a T-shirt and sometimes I'm soaked with sweat. In the end, I've made two tapes, so I've made a backup copy in parallel. Then I still have to listen through everything again and see if everything is really okay. Then, after all the work, I have to make a decision: Has this turned out really well, or: Yes, this is actually great, but not quite at 100%. This realization sometimes hurts. Then I just have to do it again.

Claus: You dig deep into this work. Do you sometimes ask yourself whether it's worth the effort?

Christoph: Exactly. Why do the whole thing at all? Do I just do it so that the record company has a new edition and can really make money from it? Or do I do it because it has an importance, a relevance, what the listener, who has the right ear and the original record, then hears? And I think: Yes, the result is beautiful, it sounds like my original record, but just a little bit better. Not different and not more distorted, but along the lines of: Oh yes, that's right, that one part, I didn't like listening to it so much before because it just sounded a bit darker. But now everything fits together. At that moment, the theme turns positive and the effort was worth it. There is a point at which you ask yourself: how far can you go, how far do you want to go? And at a certain point to say: You get a better result digitally, that would work. So this whole consideration of being "AAA" just to have this third A. Then it's not worth the effort. So I'm just working on getting that 110% with analog technology.

I have now described all my work. Sometimes it's exhausting. But this tweaking to the last point, hearing the result and thinking: Yes, there's music on it. That's a lot of fun. That's what it's all about. And usually you can do a lot more than you think.

Claus: Thank you very much for this deep insight into restoration work.

Information about Christoph Stickel and his work can be found on the homepage: https://www.csmastering.com/.

Text and photos: Claus Müller

Translated with DeepL.com (free version)