Tung-Sol
This is a variation of the 6SL7 made by TungSol. According to the TungSol manual, the difference is the brown micanol base, minimized leakage and gas currents and both triode units have balanced plate currents. Clearly, this is a "premium" version of the 6SL7. This great tube gives a great sound and will last a long time. Most are very old, produced during the '40s and '50s. Pretty nice selection on hand today, but they are disappearing fast! Come 'n get 'em
Tung Sol 6SL7
6SL7 TungSol: This tube varied alot during it's production lifetime. Earlier versions look very similar to the RCA's since they also had the black coating inside the tube. Early versions also had cylindrical black plates like RCA's. Later versions had clear glass Later ones produced during the 50's and 60's had flat gray colored plates and look more like their 6SN7 counterpart. The 6SL7WGT is the military version and usually will have more support than the commercial version. More support usually equals less microphonic problems. (Note that the "W" in the suffix of any tube means military ruggedized) Some of them also had brown bases which are probably repackaged military 6SL7WGT's. Any of hese will certainly outlast and sound far better than ANY of the S H I T produced today.