Devised, researched
 and written
  Peter King Smith BSc

                                                         The mid-1960s, German-built multi-track tape recorder with FM/AM/SW radio


Siegfried Apitz, Dipl.-Ing.

Siegfried Herbert Apitz, co-inventor of the Schaub-Lorenz Music Center, recalls his involvement in the design and development of that unique, multitrack tape recorder in the mid-1960s, and other inventions.

Photo: Siegfried Apitz  ± 1963
in the Development department
at Standard Elektrik
Lorenz, Altena, Westphalia, Germany

PKS: Do you remember much about the time when you helped develop the BBG [ed. the Schaub-Lorenz Music Center] at the Graetz company, in Altena, Germany?

SA: That was a long, long time ago. While we were still developing the Music Center at Graetz, the company was taken over by Standard Elektrik Lorenz (SEL). Much later, SEL became part of Nokia. I no longer have anything about this machine in my possession; I haven't even got one of those machines anymore.

PKS: I have three of your 5001 Music Centers in my home.

SA: Ha, ha, ha! [laughs heartily].

PKS: I am also very interested in the 5005 model, the one which contained a record player, radio and a tape recorder in a cabinet. Do you remember that model?

SA: Wait a minute…oh, yes, you mean the 'huge box'!

PKS: In England, we call it the 'radiogram' model.

SA: Ha, ha, ha!!" [laughs].

PKS: Can you tell me why was the 5005 ('radiogram') model not made for stereo reproduction?

SA: Stereo reception in Europe was in its infancy in the early 1960s; there was not much stereo available back then. So it seemed to us that a 'mono' version of the Music Center to be more appropriate for Europe. However, in the US they already had FM radio transmission, so a 'stereo' version was more appropriate there. The stereo version required a bigger cabinet to house the speakers [1], and the size of the product was more acceptable to American consumers.

PKS: While carrying out research for my website, I found very little about your Music Center written in English, except a few US and Dutch patent applications. Many documents, mainly German or Dutch, had to be translated. I believe your story as one of the co-inventors of this tape recorder needs to be told, so I was hoping you could help me write that story so I can place it on my website.

SA: Oh, oh, oh, ooh, oooh! [groaning regretfully]. I'm not going to be a big help on this because all this took place in a former life, long, long, long ago. Since then, I've developed many products such as the VPS (Video Programming System) for ITT Nokia.

 Siegfried, please just remind me what exactly "VPS" is and what it does.

SA: This invention was used to control the start and stop activities of programmed timer recordings in video cassette recorders (VCRs) [2]. VPS uses hidden codes transmitted on Line 16 of a TV signal to start and stop video recordings.

The VCR's decoder filters this coded signal and compares it with the data in the VCR's recording timetable. Consequently, the video recorder will also automatically record delayed or postponed transmissions of any timer-programmed material.

If, however, the user disables the VPS, the hidden codes in the transmitted TV signals are ignored. In that event, the start of recording will be based on the start time that the user has programmed. The VPS system only works with stations which make use of VPS data transmission. [3]

PKS: I assume that Standard Elektrik Lorenz [ed. SEL] patented this invention too?

SA: Yes, but the main patent for the VPS system expired in 2006. Although the system is still in use [4], licence fees no longer need to be paid now.

PKS: These other inventions of yours are of great interest to me, so I have made some notes about them. However, let's return to your involvement in the development of the Music Center.

SA: This old Music Center was developed so long ago; it was in my former life...

PKS: Do you remember what problems you had with the manufacture and/or design of the Music Center?

SA: I think the problem was due to the machine's huge storage capacity, which made it relatively expensive to produce. The other thing was that we didn't have the courage to spend more time on it. Not us, the inventors, but the company.

PKS: I understand from my research that many machines were returned to SEL by unhappy retailers because they were faulty or unreliable.

SA: Mmm, mmm.

PKS: How did the team respond to this?

SA: We had lots of stereo equipment [ed. 6000 stereo model] which we [ed. SEL] sold to an American company. These units/kits or inner tape machines comprised a record/playback amplifier, pilot-tone amplifier, motor control and tape drive. General Electric bought these kits from us, and installed their own receivers and power amplifiers, and made their own cabinets.
Unfortunately, these units had problems with the 'motor control', so I was posted to the United States to work at General Electric in Decatur, Illinois, to help them sort out these problems.

PKS: What exactly were those problems with the 'motor control'.

SA: In order to rewind the tape, the rewind motor has to be coupled to the tape drum that supplied the tape during playback. This meant that the rewind motor required both a very high rewind speed and a soft-start capability.

This wouldn't be a problem today, but given the resources available to us while we were developing this machine, we only considered a negative temperature coefficient (NTC) resistor in series with the motor to be suitable for this purpose.

The problem was that the person operating the Music Center had to be able to interrupt the rewind function at any given time. Consequently, when rewind was restarted, we found that the NTC resistor had already preheated, therefore making its impedance low. This caused the motor to start too quickly. Balancing the heating up and the cooling down of that NTC resistor and its mounting, created many headaches for us.

PKS: What else were the 6000 stereo model used for?

SA: Quite a number of these units were also sent to the Kennedy Space Center where they were used for recording 'space communications'.

PKS: What exactly do you mean by 'space communications'?

SA: The people at the Kennedy Space Center were investigating the possibility of recording space-flight communication such as, for example, the verbal interactions between astronauts and ground control, and the communication of data from unmanned space vehicles to ground control. However, they were not very willing to disclose much about their plans, and only wanted to know what the capabilities were of our recording machine.

PKS: My research shows that a container-load of these 6000 stereo chassis came back from the United States, perhaps because they were not needed or because the market wasn't interested. A number of them ended up in England, Holland and Germany, and were sold in kit-form for self-assembly. They were apparently quite popular with radio enthusiasts and electrical engineers, but did not contain a stereo amplifier or stereo tuner as you probably know...

SA: Ja, ja. They would have had a record/playback amplifier, pilot-tone amplifier, motor control and a tape drive just like the kits sold to General Electric. What you have just told me is possible, but I did not know about this story at all - that they came back and were distributed around Europe. I was busy enough at the time working on more new inventions.

PKS: Can you think of any other reasons why the Music Center was not a great success?

SA: Ja. First of all, the tape had a limited capacity. Moreover, you could not exchange the tape drums, except during repair. The average consumer could not do this himself, because you need a technical understanding of how to carry out readjustments. Then came the introduction of the cassette tape by the Philips company in 1963.

PKS: OK, this confirms my research. Incidentally, I am curious to know what you were holding in your hands in the photo you sent me? [see photo at end]

SA: That tiny beast is an early example of our later enemy: an audio cassette.

Aaah, yes, I thought it might be. Siegfried, you were a very interesting and prolific inventor. Based on my research, you have some 65 patents with your name on them.

SA: Ja, ja. Inventions took up much of my time, including weekends and holidays; I was busy all the time. As time went by, I had to somehow erase a lot of information from my brain about earlier inventions in order to create enough space, you know, for ensuring that the products that were developed from those inventions performed in accordance with their patented claims.

PKS: Did you ever write anything about your life as an inventor, or any articles for the companies you worked for?

SA: No, no...

PKS: My guess is that you've been retired for four years now?

SA: Oh, no, a little bit more. Wait a minute. I retired when I was 64, and was born in 1933, so I am 75 years old now [ed. retired 1997].

PKS: Were you born in the town that you are speaking from now?

SA: No, I was born in Berlin. The place where I live now is close to Pforzheim, where I lived and worked until my retirement. I am now living in Schömberg, Germany, which is 17 km south of Pforzheim.

PKS: Am I right in thinking that the Music Center was manufactured in Pforzheim?

SA: The Music Center was first manufactured at Graetz in Altena, Westphalia. That was the beginning, and where the main development of the Music Center took place. Later on, it was manufactured in Rastatt [ed. 47 km south west of Pforzheim], I think.

During the time I was in the United States to sort out the problems at General Electric, the company (including the design and development team) moved from Altena to Pforzheim [5], and the manufacturing department to Rastatt.

I was out there [ed. US] for about a year or so (1966-1967). When I returned from the States with my family, we moved house from Altena to Pforzheim.

PKS: You worked together with Friedrich Knochenhauer, didn't you?

SA: Friedrich Knochenhauer? Ja, ja...

PKS: He was an inventor like you, and a colleague, I believe?

SA: Yes, but he was my boss when I joined Graetz KG in 1962.

PKS: My research suggests that he was the main driving force behind the development of the Music Center and was its principal inventor. Is that correct?

SA: Ja, but I cannot be absolutely sure.

PKS: OK, no problem I will return to him later. Do you know why the development team chose a track duration of 22 minutes for the tape recorder? Was it because a single record in those days lasted 3 minutes and therefore you wanted to enable users to record 7 singles per track?

SA: The reason was simply to get a tape thickness which could somehow handle the high rewind speed for the short rewind times we were aiming for. So, at the time, the track duration [ed. one tape run] was not really calculated as a goal of the whole project.

The Music Center was a compact design. We made many measurements trying out different tape speeds. OK, the machines had to run at the same speed, but we were not tied to one particular speed, because there were no exchangeable parts, by which I mean that you could not exchange one machine's components and install them in another.

We just went for what we assumed would be the best compromise between reserve in frequency response, rewind time, tape thickness, tape durability and drum dimensions.

PKS: One of my website contributors has a 5001 Music Center. He removed one of its pulleys to slow down the tape speed and managed to extend track duration from twenty-two minutes to thirty minutes so he could record half-hour radio programmes [6]. Twenty-two minutes seems a strange track duration, especially as radio programmes [7] tended to be around 30 mins long, don't you think?

SA: Ja. Using a pulley to slow down the tape speed to give a track duration of thirty minutes was within the performance range we were aiming for with our machine. However, the tape and the tape heads also had to be designed at the same time during the Music Center's development, and we did not want to risk any performance loss resulting from trying to achieve a longer playback time per track.

Only afterwards, when the final production model was completed and tested, were we able to determine that there would have been no performance loss resulting from reducing the tape speed. We had deliberately built in a lot of 'reserve' at the outset, by which I mean frequency response.

We didn't push the equipment to its limits, so in hindsight, a thirty-minute cycle would not have been a problem.

PKS: I can imagine that you had other considerations that were more important than the track duration?

SA: Ja, ja. Another was the thickness of the tape. We also used different thicknesses, and eventually found an ideal combination of durability and storage capacity.

PKS: Were the black tapes better than the brown ones?

SA: Yes. The brown Fe tapes had a smoother consistency, but were less temperature resilient than the black (dark) Cr tapes. The same applied to both the carrier material and the tape's coating. The 'smoother tape (Fe) offered several advantages over the black Cr tapes. Brown Fe tapes achieved an optimum tape-to-head contact whereas black Cr tapes had a very long time performance (durability).

Although head wear was lower with Fe tapes, head soiling was higher with Fe tapes. If the tape surface is soft, the tape-to-head contact could result in tape particles being removed from the tape and deposited on the surface of the tape head. A thin deposit would increase the gap between the surface of the tape and the head, resulting in a loss in performance, particularly recording performance.

PKS: I guess this also happens when using audio cassette tapes?

SA: Ja, the same thing happens when you record over and over again on a cassette tape. Magnetic material gets scrapped off the surface of the magnetic recording tape, depositing a thin magnetic layer on the recording/playback heads, causing similar problems during recording/playback.

PKS: One theory is that the inventors may have had 'autoreverse' in mind when they were developing the Music Center. This theory arose because the tape-run indicator's left scale is printed 0-22 minutes from top to bottom and its right scale from 0-22 minutes from bottom to top.

The theory goes that after recording music on say track A1, the tape unit would automatically switch to track A2 and seamlessly continue recording, alternating the take-up drum used every 22 minutes, for up to 46 hours. Had
autoreversebeen on your minds then?

SA: No, no. The reason why the tape-run indicator scale was printed in both directions was that it was supposed to indicate the number of minutes of recording time so far (left scale) and the remaining minutes of recording time (right scale).
We also thought that having two separate scales would offer users a simple, visual representation of how much recording/playback time had elapsed, so you wouldn't have to bother about subtracting the number of elapsed minutes from 22.

PKS: OK. That makes sense. So would 'autoreverse' have been technically feasible in the Music Center?

SA: No, no. This idea would not have been possible to achieve with our machine, due to the construction of the head carrier, and because the components which operate the two tape movements would not have allowed recording in the reverse direction.

PKS: Was that because of the tape heads you were using?

SA: Ja. The type of heads and the construction, as I just mentioned. Furthermore, the head carrier is constructed in such a way that the two heads (record/play; erase) hang in a lever which pulls the heads towards the moving tape when the play/record function is operated, rather than pushes them against the moving tape.

In addition, tiny air bubbles build up between the layers of tape as it is spooling around the take-up drum during playback or recording (forwards); driving the tape in the opposite direction to make 'reverse recordings' would have generated too much wow and flutter, and would have impaired the quality of sound reproduction.

PKS: So it never occurred to any members of the team to try to design the tape to record/playback in both directions?

SA: I don't think so. That was not our intention.

PKS: OK. That puts an end to that line of speculation.
I don't expect you remember all your patents, but do you remember one of the main patents called
 Tonbandgerät mit einer Mehrzahl von Tonspuren [ed. Tape recorder with multiple soundtracks; Main Patent No. 2]? This was invented by you and Friedrich Knochenhauer, wasn't it?

SA: Ja.

PKS: The invention seems to involve recording a pilot tone at a point on the track where recording is stopped. This way, the tape recorder knows where the end of the recording is on the track during playback, as soon as it detects the recorded pilot tone. Is that a fair summary?

SA: It's slightly more complicated than that. Let's suppose that Track 7 contains a recording of 20 mins of music. Track 7 is of no interest anymore, and so you decide to make a new recording on Track 7, but this time the recording only lasts 15 mins instead of 20 mins.

The pilot tone is always recorded on the tape when recording is stopped, so now when you replay Track 7, a tape rewind is automatically triggered after 15 mins, as soon as the pilot tone is detected. In fact, there is still another 5 mins of music left from the former recording on the tape, located after the recorded pilot tone, between minutes 15 and 20

PKS: So the fact that 5 minutes of music from an earlier recording never gets played by the Music Center in fact distinguishes itself from its successor, the audio cassette tape, which as far as I can recall, would play everything, both the 'new' recording and what was left of the 'old' recording. Is that correct?

SA: Ja. Correct.

PKS: Another patent I came across is what I now call Main Patent No. 1 on my website: Magnetbandgerät zum pausenlosen bzw. wahlweisen Abspielen von Informationen, insbesondere Musikstücken [ed. Tape recorder with continuous and/or selective playback of information, particularly music].
This patent mentions five inventors of the Music Center, including yourself and Friedrich Knochenhauer. I recently discovered in Erfurt that Friedrich Knochenhauer died back in 1973/4.

SA: Ja. He has been dead for a long, long time.

PKS: This is most unfortunate because now I will not be able to talk to him about the Music Center invention or about his life as an inventor-engineer. Do you know whether he wrote anything about his life, his inventions or his work? [8]

SA: I do not think so...

PKS: No. What a pity.

SA: Because his death was relatively sudden, there was no time for him to sit and reflect on his former life, no time to recall what was important or what people should know. There was, I think, no time for him...

PKS: Do you remember anything about the team of inventors, for example, how old they were in 1960, and who did what?

SA: Ja. Friedrich Knochenhauer was my boss and the head of the development team. He was about 50 then, I think. Alexander Boom was FH's boss and the director of the Graetz company in Altena. Hans-Georg Fuchs and Gunter Löffler were both at least 40 years old, and I was the youngest member of the team at 27. We were all design and development engineers.

PKS: What about Kurt Senglaub [9] - a new name that I came across in the German document I was given in Erfurt? He was also part of your team, wasn't he? So do you know why his name does not appear on any of the Music Center patents?

SA: Ja. He also worked with us in the development team in Altena, and I believe he was responsible for the mechanical design of the Music Center. I don't know why he was not mentioned as an inventor, you can better ask him.

PKS: Could you perhaps tell me about some specific activities you were involved in while developing the Music Center?

SA: Ja. We were working very closely with the tape manufacturer for our BBG machine [ed. Music Center]. I was involved in carrying out audio performance and tape-durability tests. The tape manufacturer would not reveal what the secret ingredients were for the carrier material or the magnetic coating.

Unable to produce the right kind of tape material ourselves, we finally achieved wonderful results with both BASF and AGFA tapes. This didn't really bother us since we were busy enough with other work.

PKS: Siegfried, my Music Center does not contain a fan, but screw holes in the chassis indicate there was an plan to install one. Why was that?

SA: Aah, ja. The final production version of the Music Center had a magnetic tape, and so a fan was not necessary. The development team wanted the machine to make as little noise as possible when running or playing back music/programmes.

PKS: Oh, I see. Are you planning to write anything Siegfried?

SA: No, I think it's too late. I don't think I am an important person, and my life is not worthwhile talking about, nor writing or reading about.

PKS: Please allow me to disagree. You are the sole inventor or co-inventor of an extraordinary number of inventions; they will go unheard of if nothing is written about them. That would be a shame, wouldn't it?

SA: The things I invented and/or developed to a sufficiently high level of performance did make me rather happy. Unfortunately, my wife was not so happy about my preoccupation with my work, which I regarded to be more important than taking holidays or days off, especially if I could make the user of a product even happier. Even though the user would never know what I sometimes thought or felt about the product I was developing.

Obviously there were times when I had to deal with negative results, or lack of time, or not being able to achieve the original goal that had been set for a product. But I don't find anything unusual about that. After all, that's life. I have no regrets. I did it my way. I had to make a living, and now I finally have more time to spend with my family.


Siegfried Herbert Apitz talked to the website's author
on 21 May 2008 and also corresponded for a while.
© Peter K. Smith 2008

1. The 5005 had 4 speakers; one big one, a medium-sized one and two small ones.
2. More commonly known as 'video recorders' in the UK/Ireland.
3. Three patents are involved here:
DE 11737C2 and DE 3512156C2. These were applied for by Standard Elektrik Lorenz AG (SEL) in 1985 (pub. 1986) and were the sole invention of Siegfried Apitz. SEL combined these two patents under European Patent number EP 0256152B1, renaming them Method for generating a switching signal in a broadcast or video receiver (pub. 1988).
4. In Germany and Europe.
5. This was in 1967. Date confirmed by Mrs Rapp, FH's secretary.
6. Further details on how this was done, see Jim Weir - Lord of The Rings.
7. In UK.
8. Since this interview took place, I discovered an article about the Music Center written in 1965 by Friedrich Knochenhauer (see Journals).
9. For more behind the exclusion from the patents, see the Interview with Kurt Senglaub.

1. Apitz made the move from Altena to Pforzheim in around 1965.
2. See also Patent No. 3 regarding 'grasshoppes'.