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I have a Fender Super Champ X2, a couple years old (bought it used).

When I first turn it on, it makes a noticeable, but not deal-breaking, swirling/whooshing noise for five or ten minutes until it's "warmed up" and then it's quiet.

Is this something that new tubes will fix? Or is it likely an electronics-related problem?

  • If the problem only exists while it's warming up, most likely it is some part of the power supply slowly "dying of old age," or the tubes are getting near the end of their useful life. If swapping tubes doesn't fix the problem, you need an amplifier technician to fix it unless you already have some experience working with electronic circuits. – user19146 Mar 27 '17 at 7:36
  • Reminds me of the anecdote in one of Feynman's autobiographies, "He fixes radios by thinking!" . At high-school age, he fixed a similar static-y sound in his neighbor's radio by swapping tubes so the slow-heating one controlled the gain, and the noise from the fast-heating one was suppressed. – Carl Witthoft Mar 27 '17 at 11:47
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Five or ten minutes is not tube warmup (which is more like 15sec) but rather the warmup of other circuitry. That may include bad solder joints.

It's often possible to hunt such thermal problems down using a bottle of cold spray (which is specifically used for such diagnosis). Of course, you don't want to reach the hot tubes with that in order not to cause the glass to crack.

Thermal problems are really time-intensive to hunt down. The usual culprit will be a capacitor with instable dielectric.

If your sound disappears in a hard manner, like switched off with a switch, it is more likely a bad solder joint as opposed to a bad capacitor than when it just abates gently.

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There is so much broadness to your question. One faulty cable can bring a whole amplifier down, but here are some common factors that you should try out:

  1. Test if there is a faulty tube. You can do this by turning on the amp and set the volume fairly high. Then grab a pencil a lightly tap each tube. If one of the tubes rings or clinks through the speaker then you should look into replacing that tube. Here and here are good visual aids.

    Make sure you get tubes replaced by a professional, there are many electrical dangers that can be deadly within amplifiers. Also your amplifier will need to be re-biased and unless your a sound/electrical engineer it's not worth doing it on your own.

  2. Try turning all of the pots on the amp. Sometimes old pots can cause many electrical issues within your amplifier.

  3. Make sure your speaker is getting the recommended power input. Sometimes when people change their speakers they don't check what power rating they best suit and end up having broken amplifiers.

  4. Circuitry issues is a big one. If an amplifier doesn't get covered properly the amplifier ages faster and dust and cobwebs become apart of the circuit.

Overall, it seems to me that you might have an issue with the circuitry that controls the tubes because of the relationship you mentioned between the tube warming time and the swooshing noise. However, I don't think it will be a direct issue with the tubes, rather, an issue with the electrical circuitry because broken tubes tend to create a buzz in the amplifier and other noises.

My suggestion is to take your amplifier into a amplifier tech and get them to run circuitry diagnostics and fix your amp! :)

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