Hi Slowhand. Yes... I have used it and would say it is a decent tube, but to be candid here.... certainly nothing to write home about. The best GTB tube I have used in the syrah is the GE 6sn7gtb sidegetter. They are very plentiful,inexpensive[relatively speaking here] and come in both brown base and blackbase versions. They really are a honey of a tube in the Syrah, very well balanced tonally with a very solid bass punch. Perhaps a little on the sweeter side of neutral.... however, bang for the buck... ya can't beat em! They can be sourced just about anywhere for not much more than the price of a new pair of sovtek or the Chinese equivalents.