We all love our amps because of that warm rich sound that only an all vacuum tube amp can generate. The MESA/Boogie Mark series amp is one of the boldest and warmest amps out there.  However, we all know that all good things must come to an end, and in this case, thank god, we only mean the tubes!!

Tube Life - Pre-Amp Tubes:

How long do tubes last you ask, well that is an excellent question. According to the good folks at MESA, the life of pre-amp tubes is much longer than the power tubes. In years gone by, MESA suggested that one only change a pre-amp tube when it became problematic, causing noise etc. This was based on the fact that Boogie amps are such high gain machines and the fact that one can get a brand new 12AX7 that is microphonic right off the bat. In recent years however, both on the phone and speaking with various folks, it may be worthwhile to consider changing out the pre-amp tubes every ten or so years.  That being said, i have a 1977 Mark I and several 1981 mark IIB amps that are still running perfectly on their 20 year old plus pre-amp tubes. So I follow the motto that if it ain't broke, don't fix it.

Now let's say you do need or want to change the pre-amp tubes, which ones do you use, and does it matter? In the Mark series, the most important tube is the V1 tube. This is the pre-amp tube in the front row nearest to the input jack, or when looking from behind, the tube on the far right. In this location, either a 12AX7 or a 12SPAX7 is fine. They are both the same tube, but the latter is chosen specially against microphonics and is wrapped in a rubber collar. For V2, V3 and V5 a 12AX7 is suggested.  For V4, the Reverb driver, the choice of a 12AX7 or a 12AT7 is reasonable. What is the difference?

A word about the 12AXTUY7:

If a12AX7 tubes has "100% gain" then the 12AT7 has 40% less output, or put another way 60% gain.  The output is further reduced another 20% with the 12AU7 with 40% gain. Finally, with the 12AY7 a further 20% output reduction is achieved to have a 20% gain. With this in mind, some suggest that using a lower gain tube in V4 gives the reverb a better tone. As well, one can put a 12AT7 in V3 and soften the overall gain of your amp. Check it out, no harm can come to the amp and one can soften the gain quite a bit.

Tube Life - Power Tubes:

Unlike pre-amp tubes, the power tubes have a finite life. MESA gives the analogy of guitar strings, they never sound as good as when they are brand new! How long to lose that shine, well that depends on how long you play and how hard you drive the amp. the tubes are essentially akin to a light bulb, so the more they are on, the more they are used up. Now that being, on is defined by "active" current running through the tubes. By this, I mean that the 60/100 switch, or Simul-Class switch is in the up position so that the inner pair of tubes are being used. My man at MESA tells me that a pair of tubes in the inner sockets that is left in the 60 watt or Class A position will last a very, very long time.

So when one decides that the power tubes are used up is a matter of personal taste. I use my amps often, but don't run them hard, and I find I can get four to five years out of the power tubes. My first Boogie, a 1981 Mark IIB is still running sweet on the original Sylvania tubes!!

Bias:

Now when you go to replace your Mark series power tubes, you will run across the quagmire known as bias. Power tubes, unlike pre-amp tubes, require that the bias of the amp be set to the range of current that flows through the tubes. Randall Smith has written an outstanding article on the very subject and I would suggest that you read it. I personally am a big fan of the Randall smith Approach, and that is to make all his amps as fixed bias, so that at the time of power tube replacement, all one has to do is drop in a set of tubes in the correct range.

Tube choice:

there are a few options here. First, one can stick with MESA tubes that are available direct from them, and I have a page on this site about that very thing. Now keep in mind that all tubes are made by one of a small number of manufacturers in the world, so as long as you can find a tube that is in the range that the Boogie Needs, then using them is fine. for the Mark series amps, they were initially designed around the Sylvania GC6L6 power tube. In the late 1980's these tubes stopped being produced in the USA. There are many excellent options out there, but I think that the hands down winner is the Svetlanna 6L6. It has a nice bold, smooth tone that I find replicates the tone of my original sylvania tubes perfectly.

I have tried several tube re-sellers, but the best by far in my experience has been the lads at thetubestore.com , a company based out of canada's steel town. they have excellent process, outstanding service and are Boogie friendly. Their web site is easy to use and they have a great selection. One orders on line, and the forms allow you to enter in your special need, namely that you have a fixed bias MESA/Boogie. Tell them the year and the model number and they will send you what they feel will work best for you. they use a perfect pair plate current measurement system so that one knows the current draw of the tube. this number, for a Boogie falls in the 17 to 25 range based on this system. Next time you order some power tubes, you can specify the number that worked best for you, or have them ship a set that falls in that range. I have been really pleased and highly recommend them and the SED 6L6 tubes.  check them out at: