Mesa Baron

Thanks so much! I am indeed still on that quest, since buying Baron #54 in '96, and will try it. Mesa used to recommend a passive pre. I have also used an AR LS-15 pre (for many years). Would suspect your advice applies to all transformer-based passives preamps. IMHO, if your amp lacks the tri-tube mod (and their capacitor mod) and you are using 6L6's or 5881's, you are missing the boat; EL-34's sound far better in that amp. However, higher voltage, so they are less reliable; it goes in for repair every few years. Like you, I may upgrade everything else, but the Baron will be passed to an heir.

I can only imagine how difficult and expensive it would be to send the amp back to Mesa for the mods, from Malaysia! You might be able to get it done locally with advice from Mesa. The mods cost almost $1000 in 1998; they included better caps and 3-way switches which help prolong tube life. Yes, Mesa does sell (and match) tubes, and they say that the 6l6's they offer now sound much better than the 5881's it originally came with. Depending on whether you got it through the "authorized" retail chain, I suppose, Mesa still honors their promise to sell tubes to original owners for 1/2 price. You have persuaded me to set my sights on a Bent Audio TAP-X (the only passive/transformer-based pre with remote control that I know of; if anyone knows of others, please advise). Recently, the www.trafomaticaudio.com Experience Head One came highly recommended for the Baron by one who should know.

I forgot to add that I have had the best results with old Telefunken input tubes, but the difference was very subtle and I am not sure it is worth the trouble and expense.

Marco, originally the amp was built only for 5881/6L6 tubes, although the manual implies others could be used, but recommended against it. Later, audiophiles convinced Mesa and the designer, Randall Smith, that EL34's would sound better, and a factory modification was offered called the "tri-tube" mod. Mesa then offered tri-tube Barons with E34l tubes, later finding that they were not reliable and robust enough, and finally settling on EL34's. The do sound much better in most ways, in almost everyone's opinion, but are still not as reliable as 6L6, which have a lower bias point and run more conservatively (I think). Almost any good 6L6 probably sounds better than the 5881; Mesa offers some they say sound better than the 5881's.

Agreed, there was one cap in each channel that leaked; Mesa got a bad batch of that particular cap, they were pretty unhappy about that.   Mine were replaced early on (22 or 23 years ago)  Except for blowing bias resistors every few years, while using El34 tubes, (the 4 bias resistors are user replaceable if you have a little skill with a soldering iron) it has been completely reliable.   The bias resistors as a point of failure was an intentional design choice, sort of a backup to the fuses, of which there are 3 per channel.   As an aside, “upgraded” fuses were a downgrade. 
   I eventually got tired of replacing the bias resistors, and at the urging of Mesa, went back to 6L6 and 5881 tubes, the way the Baron was originally designed, and that problem went away.  I preferred the midrange sound of el34s, but the 6l6s sound fine, and have a little better bottom end.  Everything’s a trade off.
    It’s still going strong, after 24 years.  Occasionally some noise, about time to see if Mesa will replace the ps caps.  The same tech at Mesa is still there, and he has dissuaded me from that a couple of times, “if it ain’t broke...”  Their customer service is nonpareil.
  My only complaint is about running a space heater in summer, but that’s the price for running an amp with 12 power tubes,