I've never changed tubes before, and my amp is making loud, random crackling sounds, which is why I think the tubes need to be changed. It's a Jet City 5212RC, and has two 6L6 power amp tubes, and six 12AX7 preamp tubes. Will any 6L6 or 12AX7 tubes fit and will they need biasing or not (I still don't really understand what that means, so if someone could explain it, that'd be great!)? Does anyone have any recommendations for tubes?

This crackling happens when the amp is not being played through, but is still on.

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Last edited by HenryB at Apr 8, 2012,
Any will fit and you don't need to bias. Check out JJs from Eurotubes.com

Full retube kits! These will drop in fine: https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=247&sub_category_id=251
Last edited by Wisthekiller at Apr 8, 2012,
Biasing your amp basically means to match the voltages over all the power tunes.

You don't need to bias an amp with a tube change, but you should.

I would suggest taking it to a tech. Biasing an amp can be dangerous (meaning deadly) if you don't know what you are doing or have the proper tubes.

As for the tubes themselves, any 6l6 or 5881 type tube will work. 12ax7 tubes are universal as well.

I would suggest JJ, Mullard and Electro-Harmonix brand tubes.
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Biasing will depend on whether your amp is adjustable fixed bias or non-adjustable fixed bias (sounds like a contradiction in terms, I know). If it's adjustable, there is a trim pot or variable resistor that sets the voltage for the tubes. If non-adjustable, there's just a resistor and it cannot be changed without swapping out the resistor. Not sure which type your amp is.

I would do what Wisthekiller said and get a kit of JJs from Eurotubes.com. JJs are about the best modern tubes available without paying a lot. The noises are probably tubes, but if you change them and the noises persist, take it to a tech.

EDIT: I see you're not in the US, so Eurotubes.com won't be the best option. Check around and see what web retailers you have on your side of the pond.
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Last edited by BCKRedBaron at Apr 8, 2012,