Express 5:50 tube alternatives

[jpierce]

I'm playing a Les Paul Std through an Express 5:50 1x12. Happily getting in the neighborhood of a PeterGreen-DannyKirwan-TrowerProcolHarum-Allman kind of 1969-70 sound.

When I get the guitar and amp set to a sweet spot for playing below the 12th fret, I get a really unpleasant chirp when the pick hits the high E string beginning above the 12th fret, especially when I want to play pull off triplets. (I tend to play lead with the toggle in the middle position.) This has me thinking about swapping out tubes (after reading a bunch web pages about this tube and that tube). So, I'm trying to decide whether to swap in Mesa 5881 STR 425s or Groove Tube 6L6GCs. (I read somewhere that GTs do not void Mesa's warranty.)

Which do you think would be better choice?

Also can you swap in a 12AT7 into the last pre-amp stage safeley. (That worked really great at smoothing and sustaining the tone on an old Legend Model A. But that has solid state power.)

 

[jpierce]

With humble apologies to guitarzan. It was in your article about Mesa and tubes that I read that bit about not voiding their warranty with Groove Tubes.

Which leads to another question. Would going from a Mesa Gray (GT 5) to Mesa Yellow (GT 4) be a good idea? (A round about way of asking, do I have to use Grey Mesas/ GT scale 5s if my 5:50 was shipped with Gray tagged power tubes?

Mesa v Groove Tubes scale (per Myles, March 28, 2006)
Red = 4
Yellow =4
Green =5
Gray =5 << what my 5:50 was shipped with.
Blue =6
White =6"

 

[MrMarkIII]

The colors just match tubes in pairs. IOW, it's best not to mix a red with a grey, etc. But you can replace a pair of greys with a pair of yellows, also etc.
But wait, there's more!
I just saw a recent post by a guy who preferred the sound of a red with a blue, so there you go.