[ckullmann1]

Hi, I bought my 400R back in January 2016 and have put a lot of hours on it since then -- approximately 30-35 hours per week on average OR approximately 10,000 hours in total. Is it a no brainer to replace the tubes or should I wait until I hear some kind of noise distortion or hum/hiss? I have an extra pair of stock tubes, but I don't want to replace the tubes (and go through the process of opening up the amp) for no reason.  Conversely, I'm happy to replace them if they are due and it will improve the sound. Any thoughts would be appreciated.  Thanks - Chas

[trebejo]

Ah, these x00R amps spoil the tubes, they last forever... but once the idea of a tube gone bad gets into my head, some swapping usually happens. Even if not permanent, for experimentation at least.

Fatigued tubes sound like...like...like they're running out of gas? 

If you're not comfortable or eager to replace the tubes, you should probably call Frank. There is a version of the 400/600R that has a bit of high voltage somewhere near the tubes. It is supposed to be a user-replaceable part afaik, but the user needs to be aware of how to do these things safely. If you have done it once or twice, then it takes about five minutes.

If you ARE comfy with tube swapping, well, it might be worth it just to be able to relax and confirm that the new tubes sound just like the old ones. You can then relegate the old ones to backup status and be comfortable knowing that they are a trusted reference.

[aln]

Unplug amp-wait 10 minutes and unscrew the top.  Replace tubes with your new ones (many threads on what tubes to use). Put top back on and plug in.  There you go!  PS get a matched pair of 12at7’s-Frank has them as well.  Enjoy!

[avahifi]

I suggest you unplug the amp from AC outlet and wait an hour before removing the cover (six matchine screws on the top, three on each side, leave front and rear lowest screws on each side alone. Cover will then lift straight up off.

Keep fingers away from all of the large heat fins as they might still have shocking voltage on them.

We have replacement JJ 12AT7/ECC81 tubes available $40 a pair plus shipping.

Frank