Mark IV tube question

[tacoshow]

My M4 has the stock tubes still in it and it sounds like one of the preamp tubes may be going bad/microphonic on me. I get feedback like crazy even with the master down at 1 on tweed. On full it's not quite as bad, but still rather prominent. So, I thought I'd check with the knowledgable folks here about the best tubes to replace 'em all with (aside from or in addition to the stock Mesa brand) for high-gain, tight, chunky rock/metal. What say you?

 

[visualrocker69]

A lot of experienced people here swear by Groove tubes. Just get a quad of GT6L6-GE's and for the preamp GT12AX7-M's. They are expensive though...