It is time for tube rolling dear fellows! When the audio chain setup is complete and the key components have been chosen one should concentrate on the fine details. They are usually not bringing stunning but rather subtle improvements. My audio system recently reached such a state when all its key components were on place and I decided to finally tune it. Since the amplifier is the second most important component after the speakers that it drives it is vital to take the most out of it.
I am having a valve amplifier produced by the Chinese manufacturer Line Magnetic Audio. It is a push-pull architecture based on the EL34 tubes. Connected to its 8 Ohm output taps in triode mode my Fostex BK108 back-loaded horn speakers are really rocking. The step forward my system made with this amplifier compared to the former transistor one from Creek Audio is huge. All the aspects of the sound reproduction has been improved dramatically. Sonic characteristics like sound stage dimensions, placement definition of the performers on it, tonal characteristics like tone timbre and textures have become much more believable. Transparency, detail and dynamics had increased immensely and all that brought an elevated state of realism in the presentation.
I was aware that already with its stock tubes the LM-211IA performs rather good, but I was also told that good old NOS tubes in the preamplifier stage could bring even more out of it. So I decided to roll them off ECC82/12Au7 and ECC83/12AX7 tubes used in the preamp section for it was reported that they cause the biggest impact on the amplifier performance.
Basically there are two main groups of NOS tubes that one have to consider. On the warm, vintage and organic sounding side are Mullard and Phillips tubes. On the other side associated with neutral, modern and detailed sound are Telefunken and Siemens.
It was hard to decide which one to choose so I needed advice. Than I had a correspondence with Ralph Wege from Wege High Fidelity that was very useful for making a decision. He advised me to combine tubes from both groups in order to achieve balanced and natural sound that is neither too warm nor too analytic. Either I should pick warm sounding tube for the signal splitter (ECC82) and neutral for the amplification (ECC83) or the other way.
It just happened that I stumbled upon a very rare NOS pair of ECC83 Phillips Miniwatt long plates from 1958 so I bought them. ECC82 tubes are also very important, because they are taking care of the signal splitting in the preamp stage. Shortly after I decided for matched pair of NOS ECC82 Siemens silver plates.
Putting the Siemens ECC82 as phase splitter in preamp stage brought quite an obvious improvement. Articulation and detail have seized the place of the former haziness. The definition of each single tone has been quite noticeably improved. The transients — these micro fragments of time in which a sound is born or dies — has gained resolution that lacked with the Chinese stock tubes.
With the Miniwatt it was not as easy. I have to say that initially they sounded quite rough and even harsh. The whole presentation have become I would say retro. I was really disturbed by the fact that spending a small fortune on these tubes, they did not delivered what I expected. I contacted Herr Wege again. He explained me that the Miniwatts are really NOS tubes, that means they have not been working even an hour and need minimum 5 days of working before they reach their best. So I did, I leaved them working several hours a day and already after 2 or 3 days the things have been improved a lot. After a week I was having the impression that these are another tubes. That was really important conclusion — one can’t judge the quality of a tube before giving it enough time to opens up.
The Miniwatt tubes sound somehow fuller and bolder, the music have more body and the bass is richer and deeper than before. And it reaches new depths that I didn’t think possible for the speakers I have. Despite all these positive sides, probably because of the smoother sound they produce I thought that they might lack a bit of a detail. After extensive listening swapping tubes back and forth and comparing the sound delivered by the speakers with the one from my reference headphones I realised that what I took as a detail was actually sort of graininess that the cheep Chinese tubes were adding to the textures, or they just missed something that makes the textures organic. At the end I have to say that with the time these tubes have become even better. I am quite content with them and the improvement that this tube rolling experiment brought.
As conclusion I have to say that rolling tubes with NOS selected ones made a subtle but vital difference by transforming the former bodiless mixture of sounds into an organic, richly textured and realistic presentation. As the old saying says the devil is in the details and this is the case when it comes to tube rolling. One should not start with it before the whole system is sorted out. I would advise to leave the rolling for the very end. Before this, one should first find out what cabling suits his system best in a given budget. Interconnect and speaker cables needs especially careful selection which ideally should be made before starting with tube rolling.