Rolling Tubes

It is time for tube rolling, dear fellows! Once the audio system is complete and the key components have been chosen, one should concentrate on the fine details. They usually do not bring dramatic improvements, but rather subtle refinements. My audio system recently reached such a stage. All the key components were in place, and I decided it was finally time to fine-tune it. Since the amplifier is the second most important component after the speakers it drives, it is worth getting the very best out of it.

I own a valve amplifier produced by the Chinese manufacturer Line Magnetic Audio. It is a push-pull design based on EL34 output tubes. Connected to its 8-ohm output taps and operated in triode mode, my Fostex BK108 back-loaded horn speakers really come alive. With the introduction of the mighty LM-211IA in my system virtually every aspect of the sound has improved. Soundstage dimensions, the precision of performer placement, tonal colours, timbre, and texture have all become much more convincing. Transparency, detail, and dynamics have increased immensely, resulting in a much greater sense of realism.

I could already tell that the LM-211IA performed very well with its stock tubes, but I had also been told that good old NOS tubes in the preamplifier stage could take it even further. I therefore decided to replace the ECC82/12AU7 and ECC83/12AX7 tubes used in the preamp section, as they were said to have the greatest influence on the amplifier’s performance.

Basically, there are two main groups of NOS tubes to consider. On the warm, vintage, and organic side are Mullard and Philips. On the other, associated with a more neutral, detailed, and modern presentation, are Telefunken and Siemens.

It was difficult to decide which direction to take, so I asked for advice. I then exchanged several emails with Ralph Wege of Wege High Fidelity, whose guidance proved invaluable. He recommended combining tubes from both groups in order to achieve a balanced and natural sound that is neither too warm nor too analytical. His suggestion was to use a warmer tube as the phase splitter (ECC82) and a more neutral one for the voltage amplification stage (ECC83), or vice versa.

As luck would have it, I came across a very rare matched pair of Philips Miniwatt ECC83 long plates from 1958 and decided to buy them. The ECC82 tubes are equally important because they serve as the phase splitter in the preamp stage. Shortly afterwards, I also purchased a matched pair of NOS Siemens ECC82 silver plates.

Replacing the stock ECC82 tubes with the Siemens pair brought an immediately noticeable improvement. The former haziness gave way to greater articulation and detail. The definition of individual notes improved considerably. The transients—those tiny fractions of a second during which a sound is born or fades away—became much better resolved than they had been with the stock Chinese tubes.

The Miniwatts were a different story. At first, I have to admit that they sounded rather rough and even slightly harsh. The overall presentation had what I would describe as a distinctly retro character. I was disappointed that, after spending a small fortune on them, they did not deliver what I had expected. I contacted Herr Wege once again. He explained that these really were genuine NOS tubes, meaning they had never been used and therefore required at least five days of operation before reaching their full potential. I followed his advice, leaving them running for several hours each day. After just two or three days, things had already improved considerably. After a week, it felt as though they had become completely different tubes. That was an important lesson: one should never judge a NOS tube before giving it enough time to open up.

The Miniwatts sound fuller and bolder. The music has more body, while the bass is richer, deeper, and extends lower than before. In fact, it reaches depths I did not think possible with my speakers. Despite all these positive qualities, I initially felt that they might sacrifice a little detail because of their smoother presentation. After many hours of listening, swapping tubes back and forth, and comparing the speakers with my reference headphones, I realised that what I had mistaken for extra detail was actually a kind of graininess added by the cheap Chinese tubes. Alternatively, they were simply missing something that gives musical textures their natural, organic character. In the end, I found that the Miniwatts continued to improve over time. Today I am very satisfied with them and with the improvements this tube-rolling experiment has brought.

In conclusion, I have to say that replacing the stock tubes with carefully selected NOS tubes made a subtle but significant difference. The presentation changed from what had sometimes felt like a somewhat bodiless collection of sounds into something organic, richly textured, and remarkably lifelike. As the old saying goes, the devil is in the details, and that is certainly true when it comes to tube rolling. I would not recommend starting with it before the rest of the system has been carefully sorted out. Tube rolling should be left until the very end. Before that, it is far more important to find the cables that best suit your system within your budget. In particular, interconnects and speaker cables deserve careful attention before moving on to tube rolling.

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