Traditional grey glass GEC KT66 compared to PX25. A jolly site closer match than the Full Music PX25.
The old guys did always say you can use a triode connected KT66 in place of a PX25. Just has more 2nd Harmonic, lines start out the same. The old guys were on the money, but isn't it great to see such a close match?
Anyone care to send me a Chinese KT66 to trace?
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
JamesD wrote:I wonder if it was deliberately engineered that way?
How similar do they sound?
Haven't heard them.
They look linear. So does the PX25, except PX25 has the two advantages of more mu and lower Ri. the Chinese valve would need more primary inductance than is usually provided.
Because it would be considerably bass light until I have my winding set up once more, I haven't bothered with it. As Mark is showing you need the bass to evaluate properly. As it stands it would not be a full range valve. OK for a specific job I grant you. For the job of a PX25 the KT66 dances all over it's grave.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
Notice, from the most recent KT66 plot, that I have learned to trace without the horrible clumpy nodules. Learning to better use the GUI is ongoing.
I have issues with the Gui but it will be ironed out I am confident.
at the moment how I have to work with it is get everything right before I trace or it will throw up two errors you have to OK and then turn off and you have to start all over again. Also don't try interrupting it once it is tracing!
Apart from reliability of the GUI I can see no further needs arising with it in respect of information processing. The remaining hold up is purely the inability to work past 300v. So we await the next generation board with bated breath. The new idea of tracing A2 curves seems to fill that need from my GM70 trace, the information provided by the screen supply is adequate, we must apply artistic judgement as it is shakey at the low voltages because it wasn't designed for this job. I can tell you this because for one my GM70 +10v line traced with the filament bias providing +10v does not line up with the +10v line traced by the screen supply. So we know the screen supply is not exactly acurate at these low voltages. We were told so anyway. Similarly when I provided my own positive grid
voltages for the 1619 the curves were beautiful. (the only problem being it risks grid damage), whereas the screen supply was again not in line with it or as perfect art, though Ronald has shown me how to correct the art after the trace.
But look how much further on we all are, we have discovered so much. Proved some significant information which was only here say and disproved some. As seen in this thread alone.
It is an absolutely fantastic truth teller. We are no longer blinded and therefore no longer will stand being lied to.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
