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Post by Chilly Gibbons (Todd T.) on Jan 20, 2022 16:54:15 GMT -7
Here’s what I know about them. They tend to be higher mu than short plate preamp tubes. The longer plates seem to extend the lows somewhat and also seem to make them more prone to microphonics. I see them used a lot as phase inverters, but rarely in v1 positions. They are also okay as cathode followers, but are completely safe to try in all positions where a 12AX7 is used.
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Post by purpletele on Jan 20, 2022 17:25:16 GMT -7
Funny, I just replaced that tube last night in my Maz38!!
Those are a lot of questions
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Post by sharkboy on Jan 20, 2022 18:09:27 GMT -7
I’ve been reading about these, but wanted to hear you smarter guys opinion. I know the Doc uses these in some amps as phase inverters. A few questions. 1) why are these used in some amps and not others. what designates what amps they can be used in? 2) what are the advantages/disadvantages of using them? 3) are they safe in all circuits, or can they be harmful? 4) are they higher gain than a normal 12ax7 5) are they more prone to micro phonics because of the long plates? I’ll take a shot: 1. Yes, this relates to other questions and answers. They can be gainy and have some tonal effect. They can become microphonic, especially in high gain applications. 2. I like them a lot. My favorite ones have some clarity and sparkle on top and tight bass below. This is kind of what I love about a maple acoustic- a bit more of everything. 3. I avoid using them in high gain V1 or avoid adding too much gain in their stage. A friend tried a few fresh ones in his super high gain amp and they were all microphonic but worked fine in the PI stage. 4. They are within category- some are at the low end, some are at the high end. There isn’t a huge amount of gain conformity in tubes. 5. These are larger structures and it makes sense to me that that plays into the potential for increased microphonics. My favorite tube was the similar Ei long plate- the best ones were amazing, but the worst ones were awful. I think these are better quality controlled. I wouldn’t hesitate to use balanced ones in a (modern) PI stage (tweed may be different, because they commonly use a different PI architecture.)
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