Which tubes?

Discuss the stuff that makes your ears bleed.

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quyet
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Which tubes?

Post by quyet »

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?

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RectifiedAmps
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Re: Which tubes?

Post by RectifiedAmps »

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?

Post by quyet »

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.
Cheers. What's the take on mixing the two preamp tubes? Should they be the same?

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Re: Which tubes?

Post by MikeC »

quyet wrote: Wed Jan 27, 2021 2:36 pm
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.
Cheers. What's the take on mixing the two preamp tubes? Should they be the same?
Which model AC4 do you have - I ask because I just Googled it and some have an EF86 preamp tube!
Whakanuia o mea kei a koe

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Re: Which tubes?

Post by RectifiedAmps »

quyet wrote: Wed Jan 27, 2021 2:36 pm Cheers. What's the take on mixing the two preamp tubes? Should they be the same?
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?

Post by quyet »

ac4c1 10", yeah

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Re: Which tubes?

Post by goldtop0 »

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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