The stock tubes (I assume one of the 12Ax7 tubes) in my Vox Ac4 have developed that microphonic ringing, so it's about time for a replacement.
But I have no idea what to get other than JJs. All I know is the 12Au7 is lower gain, and I like that.
Just making this thread since I've seen a lot of NOS tubes floating around TM. Would it be worth going for something else? Would I even notice the difference with the stock speaker?
Which tubes?
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- quyet
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Re: Which tubes?
I’d say get a 12AT7 or 5751, a 12AV7 or 12AY7 and a 12AU7 and just try them out. Current production stuff is fine and a lot of NOS can test ‘new’ but still be microphonic factory rejects so I’d figure out what you need in terms of gain before you splash out for vintage glass.
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Re: Which tubes?
Cheers. What's the take on mixing the two preamp tubes? Should they be the same?RectifiedAmps wrote: ↑Wed Jan 27, 2021 2:23 pm I’d say get a 12AT7 or 5751, a 12AV7 or 12AY7 and a 12AU7 and just try them out. Current production stuff is fine and a lot of NOS can test ‘new’ but still be microphonic factory rejects so I’d figure out what you need in terms of gain before you splash out for vintage glass.
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Re: Which tubes?
Which model AC4 do you have - I ask because I just Googled it and some have an EF86 preamp tube!quyet wrote: ↑Wed Jan 27, 2021 2:36 pmCheers. What's the take on mixing the two preamp tubes? Should they be the same?RectifiedAmps wrote: ↑Wed Jan 27, 2021 2:23 pm I’d say get a 12AT7 or 5751, a 12AV7 or 12AY7 and a 12AU7 and just try them out. Current production stuff is fine and a lot of NOS can test ‘new’ but still be microphonic factory rejects so I’d figure out what you need in terms of gain before you splash out for vintage glass.
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Re: Which tubes?
Ah- this is an AC4C1 then? All the others have just one 12AX7 preamp tube I think. The AC4C1 circuit uses ‘DC coupling’ between the two tubes (2nd & 3rd gain stages), which may act weirdly when substituting. It won’t hurt anything to try, though. Maybe just try a sub in one of the two spots first, see how it sounds, swap them around, try it again, etc.
How much less gain do you want? If just a bit less, you could try 5751 in either socket. If a lot less, then maybe a 12AU7 in either spot.
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Re: Which tubes?
Try for yourself a 12AY7 in V1...........it takes the fizzy overdrive away as with the 12AX7.....pretty much the same volume just more headroom before breaking up.
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