I have enjoyed reading Ken Kessler's Copper series on reel-to reel tapes enormously. 146, 148, 149, 151, 152, 153, 154 and this issue – Ed.>
My first exposure to hi-fi audio came from reading Ken's writing in Hi-Fi News & Record Review magazine, and his witty and incisive writing style has weathered the passage of the past forty years. He has discussed the trials and tribulations of acquiring pre-recorded reel-to-reel tapes, but he has not (yet) touched on the subject of keeping these ancient machines running. I have some recent experience in this respect that I’d like to share. My first tape machine was an Otari MX-5050, which was a very flexible machine that could play 2- and 4-track tapes at multiple speeds and equalizations. I bought a Nagra IV-S portable tape recorder for making live recordings in concert halls, and later a Nagra T- Audio studio recorder to facilitate the editing of these recordings. The T-Audio is no slouch as a playback machine, but the playback electronics were not designed with audiophiles in mind. The sound can come across as being too up-front and lacking in finesse. I therefore wired the playback head directly to my DIY tube tape head preamplifier.
Adrian's Nagra-T tape deck.
The last time my Nagra machines were serviced at the factory was five years ago. I heard that the gentleman who had been in charge of the analog recorders and wrote the service manuals for both of my machines was retiring, and I quickly sent the machines back for a tune up. Mr. Herbert Bartels very kindly agreed to return to Nagra on a part-time basis to do the work. New heads were installed and the machines were regulated and recalibrated. Everything worked well on the T-Audio except for an annoying squeaky noise coming from the reel holder mechanisms. The noise was so distracting that I had a soundproof cover made. It is an enormous black blob that looks completely out of place in my living room, but it can be dismantled and folded up when not in use. I took to listening to tapes only when my wife was out of the house, to spare her from the eyesore. The T-Audio has two belts that drive the reel holders. There are two pairs of reel holders for 10.5-inch and 7-inch reels respectively. A short-toothed rubber belt runs between the motor pulley and the two reel holders in a triangular configuration on each side. The tension of the belts needs to be adjusted just right since under-tension can result in the belt slipping when the reels are stopped during fast forwarding and rewinding. Over-tightening can result in excessive vibrations. I have dismantled the mechanisms and adjusted the tension to no avail. I vented my frustration in the reel-to-reel forum at the What's Best Forum, a fountain of wisdom. An expert replied that the noise is due to aging of the belts; the rubber loses elasticity over time since the belts were made more than 40 years ago, and this happens even with belts that have never been used. He also knew someone who had made a new batch of belts according to original specifications. I contacted this gentleman, Tom, who does maintenance and repair work for Nagra and other brands of tape recorders. I bought two sets of belts from him for a very reasonable cost. After the belts had arrived, I went to work on the machine. Removing the old belts according to the instructions on the service manual was straightforward. However, the old belts had left some very sticky residues that looked like dried snot on the pulleys. The gaps between the teeth on the pulleys were very narrow, and I used a dental pick (a must-have in the tool kit of audiophiles, much more than just for cleaning teeth!) to patiently scrape off the globs. The remaining film of residue was then removed with acetone. The new belts were installed, the tension adjusted, and the mechanisms reassembled.
Note the dry snot-like substance sticking to one of the reel holders. It had to be carefully removed.
The machine fast-forwarded and rewound smoothly. So far, so good. I then hit play and the tape started playing for a few seconds. And then everything just stopped. I tried again with the same result. I dismantled the reel holders and inspected everything, and then reinstalled them to no avail. I inspected the circuit boards to look for signs of solder balls shorting something out, but everything looked normal. My diagnostic training kicked in and I started to go through the differential diagnoses. The reel holders were not moving, and in fact, they were unmovable by hand. The right capstan was spinning, but the left one was not. I measured the voltages. The voltages at the reel motors suggested that the electronic brake was engaged. The voltage at the right capstan was correct, but it was erratic on the left. I went through the 576-page service manual (yes, this thing is probably more complicated than an MRI machine) to try and find a reason for such an ailment. I called my recording partner who has more experience with the Nagra recorders than I do. He managed to find a table buried within the pages of the manual that mentioned similar symptoms. Apparently, the blowing of a particular fuse at the power supply board will trigger the emergency electronic brakes. I wrote an e-mail to Mr. Bartels at Nagra, but I received a reply from another gentleman informing me that Mr. Bartels had been in full retirement for several years, and that the only thing I could do was to send the machine to Nagra in France for servicing. The need to pack such a delicate instrument for shipping filled me with dread. I contacted Tom, the technician who sold me the belts. He was very kind and measured the voltages at the power supply board of a machine he had in for servicing at the time. The voltages were the same as what I found on mine, and therefore the power supply was not the issue. I started to think that the logic control board was perhaps faulty. This raised the possibility that I could just send the board for servicing, not the whole machine. And then a miracle happened. Mr. Bartels apparently still checked his company e-mail from time to time, and he answered my message. He said that there could be a faulty filter capacitor at the capstan motor. I dismantled the motor and found the two capacitors. After removing them, I measured their capacitance with my LCR meter, and they both measured correctly. Since I did not have a working capacitor tester (only an antique Sprague tester that no longer works), I installed new capacitors from my spares box. Just like that, the machine was working again. And as good as promised, the squeaking was gone, and there is now only a quiet whirling sound that is barely audible at the listening seat. But I worry that Mr. Bartels might not answer my e-mail next time. Not having a local technician capable of servicing the machine is a headache. There are now at least four brand new tape machines on the market, two from Metaxas and Sins, and two from Ballfinger. Analogue Audio Design in France will be releasing one soon. These all come with the manufacturer’s warranty and should be plug-and-play without any hassle. I have no experience with them and do not know how well they perform. Greg Beron of United Home Audio has been restoring and upgrading Tascam recorders for many years, and these too should be hassle-free. They also enjoy a very high reputation amongst audiophiles. A company in Slovakia, SEPEA Audio as resurrected the cult-favorite Stellavox TD9 studio recorder using new old stock and freshly manufactured parts. However, none of these options come cheap. On the other hand, audiophiles can dip their toes into the reel-to-reel universe by acquiring a machine from the used market. This approach will often require the owners to get their hands dirty, since most of these machines would have been lying in grandpa's basement for decades. This could be part of the fun, depending on how you look at it. Except for the Tascams, it might be difficult to find spare parts and expertise to maintain and repair ancient consumer machines. On the other hand, servicing is still available for the more popular professional machines from companies such as Studer, Nagra, Telefunken and Ampex, since many professional studios still use these machines. However, they tend to be big, heavy and complicated. As more and more audiophile-quality pre-recorded tapes become available, the demand for these machines will only increase. I will address the sources for new pre-recorded tapes in future articles Just one more thing. I recently replaced the series-resistor stepped attenuators in my tape head preamp to ladder-type stepped attenuators, as one of the switches had become intermittently faulty. I needed to rearrange the layout of the preamp to accommodate the much larger volume controls, but otherwise nothing else was changed. I was expecting perhaps the kind of differences one might find when listening very carefully and intently (and having an active imagination), the type of things non-audiophiles would scoff at. Since I had listened to a tape of the Decca Ansermet Three Cornered Hat recording the day before, I put it on again for comparison.
The two large red things are the new stepped attenuators. Luckily, there was just enough space for them, but they had to swap places with the selector switches. The downside is, the silkscreen on the front panel no longer indicates the correct knobs.
The magnitude of improvement in dynamics when I compared the tape with the LP in the past was impressive, but this time, it was shocking. I was in awe. Not only were the transients faster, but the sound had a lot more weight, and the clarity was startling. I never imagined master tapes (a production master in this case) to actually sound like this. I never realized how much of the dynamics and the detail was lost at the volume controls previously. Going from having 24 resistors (even though they were Vishay metal film SMDs) and solder joints in the signal path to just two made a huge difference. Just imagine going from the good ol' plastic volume pot straight to this. Some people are spending thousands of dollars for things like power cables when they should be spending their money first on something with far more impact like this. I wish I had done it years ago. The reason why I had not was because all the ladder types available in the past did not keep the input resistance constant at every step, but this one almost does (with a maximum 6 percent deviation after putting a 100 Kohm resistor in parallel to achieve 50 K). This is important in order for the tape equalization in my preamp to maintain accuracy. I don't think the deviation here is large enough to be sonically significant, but I will do some measurements this weekend to be sure. Even if it is, I am still willing to trade a little frequency non-linearity for the scale of improvement I have just witnessed. The thought of doing the same for my phono preamplifier is very tempting indeed…
Header image: a new Stellavox TD9. From the SEPEA Audio website.
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