Audible illusions Modulus 3A or Klyne 6L

AI Modulus Preamps Are Not Hard On Tubes... To date we have mfg.many thousands of these units and, to the best of our knowledge, premature tube failure has not been a problem. The problem is some "tube rollers" continue to substitute old-style 6DJ8 type tubes in our preamps. These tubes were OK for TV sets and RF applications but not designed for audio purposes. Thus the small plates and weak mica insulators resulting in excess microphonics and noise. However there do exist some NOS brands that are acceptable and exhibit good life; Tungsram is one brand that comes to mind.

Be advised that our tube preamps are open-loop/no-feedback designs. The advantage of eliminating negative feedback is well known. The downside is that the tube we select must be well constructed, have low-noise and good life. In our 30 years experience the best tubes we found that meet our criteria are those mfg.in Russia. In the early 1980's we did use some 6DJ8 tubes produced in the 70's that were well made but, when the supply of good tubes ran out, in 1987 we discovered Russian tubes. Primarily used for their military communications, including transmitters in MIG jets, these tubes were designed for low-noise spec.and reliability. All of our preamps since 1988 have Russian tubes installed.

Regarding our filament-on design, based on his experience with tube equipment in the recording industry, my boss had learned that the main contribution to tube failure was thermal shock to a cold tube. For that reason most recording studios left their tube equipment on. Of course, leaving tubes on does cause premature plate degeneration but he experimented with leaving the filaments on but with some current flowing on the plates. This design has proven to be a big success in prolonging tube life in our circuits.
Unfortunately this circuit design will not prolong the life of old-style, poorly made tubes. Suggest you tube rollers experiment with preamps employing negative feedback and cathode followers. Regards, Jerry/AI's Tech,

It's unfortunate you continue to imply there's is a design flaw in our circuit design by reguritating old comments that our preamps are "hard on tubes". Considering the thousands of preamps we have produced over the past 25 years I'm aware of the complaints documented by various "tube rollers" their old tubes just won't last in our no-feedback design. Needless to say it's also a well-documented fact that many AI owners have experienced excellent tube life even some owners who don't use Russian tubes. Apparently these people were lucky to find some well-made tubes.

Bottom Line, If there was a design flaw in our design then "every" preamp we make would cause premature tube failure. Regards, Jerry AI tech.

Yes I've read your 10 posts and from the 1st, in which you make the statement that "unfortunately the AI is known to be a tube eater". It's my belief that you are attempting to convince readers that there is a technical problem with our design.

I also suggest you re-read my posts in which I have attempted to, constructively, address your concerns.

Regarding the popular term "tube roller", I have no problem with a person installing a particular tube in our preamp in an attempt to "voice the sound". Our objection are those who ignore our advice and plug in old-style tubes that soon become noisy then complain that our preamp is hard on tubes.

Try plugging old 6DJ8 type tubes in another modern tube preamp design like Audio Research etc. and you will soon discover they become noisy. I also know that, for the same reason, some tube mfgs. have abandoned this tube in favor of the Russian 6H30 tube or now use another tube type like the 12AX7. AI has continued to use frame grid tubes because we feel our design has proven its reliability providing the user understand that not all NOS tubes will last in a modern-day, open-loop, no cathode follower design like the Modulus. Regards, Jerry/AI's Tech.