12AX7 ECC83 7025 not Glowing is it Broken?
A question we hear a lot here at Voc Rock. Some of the modern current production tubes and particularly tubes from Russia (Electro Harmonix and Sovtek) have fairly closed boxed plates. The heater filaments that glow red hot in order to heat up the plates for the tube to function at all are often not as visible with these tubes as with some where there is a more open box section with larger holes present on the boxed plates themselves.
So in summary you will not necessarily see a red glow with some of the more modern pre amp tubes. This does not mean there is a fault with your amp or the tubes. Please note that all the tubes we sell here at Voc Rock are tested on 2 different types of tube tester before being shipped so the chances of receiving a valve that is broken is much smaller than it could be if we shipped direct and relied on tests that the manufacturers carry out before shipping to us. Some tube suppliers are offering 2 types of tubes (standard and premium tested). Basically all our tubes are premium tested so we do not have 2 price bands.
Hope that helps.