I would say controversial. Most of the posts are innocently wrong, the remainder are BS 😎.
@mctavish do not try to discuss, it's a monologue.
Jan
@mctavish do not try to discuss, it's a monologue.
Jan
I do not read any of the "best 12AX7" or any other tube threads regardless of author because there is no "best" tube for every possible application. Is the best 12AX7 for a HiFi phono stage the best 12AX7 for a guitar amp? Is the best 12AX7 for a super high gain 100 watt guitar amp like an SLO100 also the best tube for a Fender Champ which runs a single 12AX7 into a single ended 6V6GT for about 5 watts through a 6 or 8 inch speaker. There generally is no one size fits all "best" anything as there are too many variables.
I would judge the quality of a 12AX7 based on cathode coating material quality, structural integrity of internal components and hardness of the vacuum. I have no way, as an average consumer, of verifying those properties, though.
Bad 12ax7 is one standing in a tube socket and no other input is necessary....extreme microphonics.
I have invented a circuit that I call the saturator. Intended for guitar amps, it uses a pentode tube with a bootstrapped plate load resistor to offer gains in excess of 1000 V/V with the saturation knob up full. Unfortunately, a common run of the mill 6AU6 or similar is so microphonic at this level that you can talk to it and hear yourself in the speaker. The first use of this design was in a 4 tube 4 watt guitar amp using series string radio tubes. The 18FW6 is a 6AU6 with an 18 volt 100 mA heater. Only about 20% of my tubes will work at full gain. You can't put the amp head on top of the speaker, or a good tube will become microphonic after a few hours of use.
Let's consider letting this thread sink into oblivion, feel free to start another thread covering anything from this thread you'd like to discuss further. 😀