Changing tubes for the first time

Discussion in 'Amplifiers' started by Feral McElreavy, Nov 1, 2017.

  1. Feral McElreavy

    Feral McElreavy New Member

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    Hey all,

    I'm a noob to the interior guts of these tube amps, but I'm changing my 2014 100 watt archon's preamp tubes later today. After researching as much as I can, it sounds like power tubes are too dangerous for me to do alone, so I'm sticking to just the preamps. I'll have a tech do the power section, especiallly with the potential need to rebias the amp.

    I wanted to ask, are there any special precautions I should take when changing the preamp tubes/removing the metal covers? I'll use gloves to keep my fingers off the tubes, I'll unplug the amp and put it on the "on" position for 60 seconds to drain power, I'll use electrical contact cleaner etc.. Is it safe to remove the amp from it's outer casing? I don't know how else I could reach the tubes.

    I don't particularly want to die.

    Thanks in advance!
     
  2. andy474x

    andy474x Knows the Drill

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    You'all be fine! No gloves necessary on the tubes, unless they're hot. There's an old internet/wives tale that finger oils will cause hot spots on the glass and the tubes will crack... it's BS. The place you need to be most careful is when you're actually inside the amp chassis, which you would need to take out of the head box to get to. Some recommend keeping one hand in a back pocket when changing tubes, or doing other amp work, to reduce the risk of a shock grounding through your chest (from one arm to the other). Personally, when changing tubes, I don't worry that much, I just keep that second hand off any metal parts in the amp.

    And, regarding power tubes, you should definitely learn to change your own! One of the most user friendly parts of a PRS amp is that it's designed to be done yourself. You just need a multimeter, which you can get for far less than the cost of having your amp biased. Put your multimeter leads in the check points and adjust the pot with a plastic flathead screwdriver. I would definitely recommend plastic for that as that's one spot that could potentially (albeit rarely) light you up, but don't hesitate to do it. Paying for a bias on a PRS amp is a waste of money!

    Out of curiosity, why are you changing your preamp tubes?

    PS - regarding your mention of taking the amp apart - you don't need to do that. Just take the back grille off, if it's anything like other PRS amps there should just be 4 screws. You may need to take the power tubes out to get to some of the preamp tubes.
     
  3. Feral McElreavy

    Feral McElreavy New Member

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    Awesome! Well, I believe there's been an increase in microphonics, and I'm picking up radio stations with this amp, which I've read are symptoms of bad tubes. I'm also interested in hearing what the archon will sound like with some mullards and tung-sols in the preamp/poweramp.

    As far as the amp head box goes, I think I do need to remove the chassis. I've removed the back grill, but the tubes are way in there, and they're screwed in with the metal tube covers. There's more danger with removing the chasis, vs leaving it in there?

    Thanks for your help, Andy!
     
  4. andy474x

    andy474x Knows the Drill

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    Yes - the main culprits, from my understanding, are the filter capacitors. Don't ask me what they do, but apparently thy can hold a pretty nice charge! So be wary of touching the internal circuitry if you do remove the chassis (that's the metal frame the amp is built on).

    I'm a little surprised that the tubes can't be removed with just the grille off the back. Usually the covers come off by pushing them in and twisting, then pull straight out. And the tubes pull straight out with some wiggling. Maybe they switched to something else on newer amps.
     
  5. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    You shouldn't need to take any of those shock related precautions with an Archon. Just take the back off and carefully remove the covers, then the tubes. I usually recommend gently wiggling them loose, as tube sockets are (SHOULD BE) very tight! If you don't wiggle them, you have to grip them so tight sometimes that you might shatter the glass. Grip gently and wiggle gently. And if Scott reads this, he'll be feeling dirty again!

    You should be able to easily do the power tubes as well, unless you don't have a MM to use for bias adjustment.

    I haven't done anything to my 50 watter yet but was wondering the same thing and will know before long.... how would it sound with some nice NOS glass? Even better? IS that even possible??? I bet it is. Design is high end. I'm guessing it will clearly show tube differences.
     
  6. andy474x

    andy474x Knows the Drill

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    Amps are funny like that... some are very sensitive to different tubes, even of the same brand and model. Some not so much. I had a couple of Egnater Tweakers (15 and 40) in the past, and they didn't seem to be at all sensitive when I switched preamp tubes. My Custom 50, I swapped one preamp tube and the lead channel now reacts wayyyyyy differently to the preamp EQ. Almost wonder if that tube was somehow defective. Weird!
     
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  7. Feral McElreavy

    Feral McElreavy New Member

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    I changed my tubes last night right before practice, and HOLY SHNIKES!

    It sounds amazing. Much more note separation and articulation while also being much more aggressive. There's a very noticeable volume increase as well-- which I did not expect(nor need). And this is just the preamp tubes. I'm never putting JJ's back into this thing.

    It's almost too loud, akin to my friend's 70's Marshall superbass.

    I play the archon through a mesa 4x12, and I'm not sure if I'd rather play anything else. :)

    Thanks for the help!
     
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  8. bodia

    bodia Authorities said.....best leave it.....unsolved

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    So, what did you end up putting in there? The Mullards or the Tung-Sol? NOS?
     
  9. Feral McElreavy

    Feral McElreavy New Member

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    2 tung-sols and 2 mullards, and then replaced the JJ's in the phase inversion and effects loop positions.
     
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  10. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    which tubes did you put in which slots? There might be even "more better" tones with them. And, if you get a chance, try a not fancy at all new Sovtek LPS in the PI... unless you have a nice Mullard for that too.
     
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  11. Feral McElreavy

    Feral McElreavy New Member

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    I have the 2 mullards in the lead gain (v3+v4), a tung-sol in the clean gain, and a tung-sol in the input(v1). Any suggestions as far as moving them around goes?
     
  12. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    The only change I would even try from that is swapping V1 andV2. See which way you like it best. Two mullards in the lead stages might make it not as bright as you'd like. Depends on speakers, what tones you're after, etc.

    Oh, are these NOS Tung Sol or new? If new, leave them where they are for now...
     
  13. Feral McElreavy

    Feral McElreavy New Member

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    Why leave them there if they're new? Which they are. The 12ax7 str. I'm an Adam Jones tone fan(Tool). I really like his 10,000 days tone. I play with a lp custom with an sh4 jb that I put an alnico 8 magnet into.. because I'm obsessed.
     
  14. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    Because I'm not sure of the answer to the question of whether or not V2,V3 or V4 is cathode follower position, but it is strongly advised not to use the new Tung Sols in a Cathode follower position. They are good sounding tubes but can't be used in those positions. I'm not sure of what positions in this amp might be Cathode follower positions. The only ones I'm sure aren't are V1 and PI of course.

    The TS can't handle that position, and are known to fail quickly and possibly catastrophically, damaging the amp. I'd contact PRS to make sure that V4 is not a Cathode follwer position and it if is, put something other than a Tung Sol in there quickly.
     
  15. Feral McElreavy

    Feral McElreavy New Member

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    Thanks for the heads--I will contact them ASAP.
     
  16. Feral McElreavy

    Feral McElreavy New Member

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    I contacted PRS support asking where the cathode follower position is, and they responded with "..the amp and does not have a cathode follower."

    Does that seem correct?
     
  17. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    Yes! You're good to go. Put those tubes wherever they sound best.
     
  18. Feral McElreavy

    Feral McElreavy New Member

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  19. DreamTheaterRules

    DreamTheaterRules Archon owning member

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    I'm sorry if I alarmed you. I was going to ask before I started rolling tubes into my Archon but hadn't asked yet. I didn't think they had any cathode followers in this amp but you have to make sure because the Tung Sols are not good in that position on amps that do (like my Mesa amps).
     
  20. Boogie

    Boogie SuperD

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    You will not hurt your amp experimenting with different preamp tubes (of the proper variety) in different locations. There are certain places that react definitively to certain tubes (PI and V1 in particular) but you can’t hurt anything. If it sounds good, keep it...if not, change it. As long as you don’t change tube types (AT versus AT versus AU, etc.) it will, generally, only result in a tone change, but in gain stages, a change in type (AX to an AT) can impact overall gain. So much fun is available in tube rolling, so do the research, buy some variety and experiment. Btw, new-old stock (NOS) can make a huge difference, especially with Mullard. Read up on that issue, too.
     

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