Sovtek 5881WXT+/6L6WGB and Ruby Tubes

Posted: January 25, 2016 in Mesa Boogie Dual Rectifier, Tube Amps, tubes
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(Edit: I confused some 6L6 sub-types in the original article, which I don’t think is hard to do).

I ran across this article about Sovteks and how the rating charts for several tube brands compare.  I am needing tube replacements and this seems pretty handy for finding tubes that fall into Mesa’s bias range for their 6L6GC.

I’ve been using Ruby 6L6GCMSTR, which is an excellent tube, and I will likely stick with it, but these others have piqued my interest in differences between the sub-types.


 

Yesterday, I pulled my tubes and put my stock, barely used, Mesa tubes in.  It sounded horrible.  The Rubys are rated at 38ma idle plate current.  I ended up putting my amp to the EL34 settings to increase power output of the Mesa 6L6GC.  To be safe, I began in Spongy and Tube rectifier and worked up slowly, constantly checking for red plating for 5 minutes or so, before moving up to a higher voltage.

I was able to top out at Bold and Tube, but backed it down to Spongy and Silicon to be safer.  This was done to improve the tone of this particular, cooler, set of Mesa tubes; I don’t need this with those Rubys and it doesn’t work right, anyway, because the low plate draw causes them to run too hot in EL34 mode.

(Update Edit) Ruby 6L6GC-STR and Mesa STR tubes are produced in the same factory and are the same, with one exception.  Mesa does their tests to select tubes which perform to their specifications.  Putting Ruby tubes in a Dual Rectifier requires a person to purchase a set of tubes with plate currents between 33ma and 52ma.  Whether Mesa considers any other variables, such as transconductance is not known to me.

The Mesa branded, stock, tubes I have definitely run much colder than my Ruby set and I prefer the warmer, lower plate current from the Ruby set.

 

Update (5 hours later)

I have a great sound again by following my own instructions.  It’s back in 6L6 mode, with the tube rectifier.  My old channels settings are retained.

I learned a few of things from this:

  • Differences between tubes can be largely mitigated by Volume and Send controls.
  • The higher the upper-mid level the 6L6GC is peaking at, the lower the Channel Volume will need to be to dial out grain/fuzz/fizz near 1 kHz.
  • To put #2 a different way: if a person hears an abundance of grainy fizz, turn down the Channel Volume and turn up the FX Send with the Output at Noon (or the desired “moderate” level a person wishes to be their gig volume).  Use the Send to push the preamp sound down the line, rather than pushing the loop with the Channel Volume and creating unwanted overtones.
  • If the tubes work in the amp, a person can dial in a great sound; Don’t spend more money than you have to.  Spend 3 to 5 minutes with the level controls and move on.
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