Help me pick a preamp tube combination

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by dk_ace, Mar 6, 2006.


  1. dk_ace

    dk_ace Member

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    I play a Mesa Triple Rectifier (Please don't leave my topic immediately upon reading that). I bought the amp when I was a kid with more money than brains (luckily the amp has enough options and features to grow with me). I switched to EL34's a few months ago, and it got be a lot closer to the sound in my head, but I'm still not quite there. I don't play metal (I do set CH.3 for the heavy stuff, but it doesn't see a lot of action). The sound I'm looking for is not really dark, but not shrill either. It is 3D, with plenty of chime and great upper mids. It still needs to have decent low mids though. The sound is reminiscent of some of the better AC30's I've heard. I will probably find this sound in the clean channel (probably in the pushed mode). I am not getting it now, and I think the preamp tubes are the best place to start at getting it (I've tried some pedals...treble boosters and such....really cool, but not quite what I am looking for). I have researched a lot of tubes and found lots of opinions on what works. NIB vs. NOS, re-issues, long plate vs. short, etc... With your experiences, what tubes will get me headed in the right direction? I know it's a tall order to get such a sound from a Mesa Recto, but I think it's possible. I am most interested in starting with replacing V1 (input stage for all channels on one side, clean channel on the other). Don't have a ton of cash laying around (I don't see NOS Mullards in my near future....If I did have the cash I would probably just buy another amp). Please lend whatever tube suggestions you have.

    Thanks,
    Dustin

    PS This is my first post on this site
     
  2. brad347

    brad347 Member

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    i suggest e-mailing Mike at KCA NOS tubes (he also frequents this site) he has helped me out before with recommendations and is a good guy. I was very happy with what he sent me. He will take into account your price range and work with you.
     
  3. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I'll take my best shot, Dustin: Raytheon black-plate/halo-getter 12AX7A from the early '60s (no later than '62). They've got fantastic clarity and upper-mid chime. Low mids are not accentuated, but they're still available, and very well-defined. The way they break up, into rich harmonic overtones, is divine!

    It's near impossible to find them NOS, but there are frequent ANOS (almost new, old stock; i.e. they test same as a new one should) samples available. These mostly come from old Baldwin, Lowrey, or Schober organs (organ pulls? :eek:), which were selected for low-noise by those companies. I still consider them a bargain, but the prices do seem to have been going up over the last several months.

    - T
     
  4. Reeek

    Reeek Member

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    When you swapped to EL34's I assume you had it biased, right?

    I'm asking because I have always heard that MB's were typically biased cold from the factory so if you just dropped in the EL34 and flipped an EL34 switch (if it has one), you may not be getting the true potential from the power tubes either.

    But I am not an MB expert either. I do know the value of a proper power tube bias and what it can do to the tone with any set of tubes. Sometimes the improvement can be profound, sometimes subtle but always better when done right.
     
  5. dk_ace

    dk_ace Member

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    Thanks guys! I will give Mike at KCA a try. I will also look into the Raytheon some more, it may be just the thing. As far as the power tubes go... Mesa amps are fixed bias. You can mod them to be adjustable, but that voids your warranty. I still have a year left on the warranty, so I'm going to hold out on that for now. The tubes and bias should be fine as I got Mesa tubes (I didn't get the standard el34 they use, I don't remember the exact model but it was one that was recommended for having the properties I wanted.... and it did). Feel free to give me any suggestions you have.
    Thanks,
    Dustin
     
  6. Reeek

    Reeek Member

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    That's a new one on me to be sure but then I'm not proclaiming to know everything either :)
     
  7. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Yep. I had my 2:90 modded for adjustable bias, so I could use some NOS 6L6GC, and it was much improved. Didn't have to test the warranty, but its good for people to know that they may get some flack from Mesa if they do this.

    - T
     
  8. Reeek

    Reeek Member

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    My point is that fixed biased still means that it's adjustable. No tube amp should ever be made to have a bias that can't be altered.

    Amps with trims pots are still called fixed biased. But not "Nonadjustable".

    Maybe the bias is determined by the ratio of two resistors that will allow one of those resistors to be replaced for bias adjustment. I would be way surprised if setting the bias on a MB would void a warranty. Maybe installing a trim pot would but not adjusting the bias . . . right? That would really surprise me.
     
  9. dk_ace

    dk_ace Member

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    Unfortunately, any modifying or altering of the amp circuitry voids the warranty. The bias is not adjustable in any way without voiding the warranty. This is one of the many reasons that mesa is dissed by amp techs. Randall Smith (the guy that started mesa) worked on Fenders originally, and almost all of the repairs he did were due to improperly adjusted bias settings. So he made his amp with a pre-determined bias setting (with the exception of the 6L6/EL34 switch), you are only supposed to use mesa power tubes as they come in spec for the bias of your amp. I may eventually go the mod route, but I don't want to do that right now (and the power tube response in my amp is good at the moment). Any other preamp suggestions?

    Dustin
     
  10. dk_ace

    dk_ace Member

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    In an update to the topic, don't let price be a factor from now on. If a $300 NOS mullard is the ticket to this sound, let me know. As tight as my budget it, "buy once, cry once" is still the best way to do things for me. I would really like to spend $100 or less, but if that won't get the sound I want, tell me what will.
    Thanks again,
    Dustin
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    There's no reason to be spending $300 for any preamp tube. At least at this time - maybe in 3-4 years...

    Long-plate halo-getter Mullards (etch code type f91 or f92) are spectacular: you'll hear your guitar as you've never done before. I can't say the same for later, short-plate Mullards, though - they're lacking in clarity and frequency range, in comparison. Long-plates have a more solid low-frequency response, too. I'd encourage anyone interested to invest in a long-plate Mullard. They can be obtained for significantly less than $100. You don't necessarily have to buy NOS for these, because they're generally very robust. You can get a used one, testing new, for about half the price of a NOS. Best to work with a trusted dealer for best results.

    Okay, now I've revealed my two favorite 12AX7s! Let's hear it from someone else.

    - T
     
  12. Rod

    Rod Tone is Paramount Silver Supporting Member

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    In the Mesa Rectifiers, I'd try some JJ803's their short plate 12AX7/...NOS stuff may cause you problems in V1 because of gain...The Mesa stuff is set with a nonadjustable bias!!! It's ludicrous but true....I had a Mark 1 reissue that was biased so cold that the tubes never even got warm,,,the amp also sounded like ****...screw the warranty. get the tone..heat those tubes up!!!!!
     
  13. Blue Strat

    Blue Strat Member

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    FYI, most guitar amp tube dealers can set you up with "Mesa Ready" power tubes as long as they're aware of the bias situation. No rebias required.
     
  14. dk_ace

    dk_ace Member

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    :confused: What kind of problems? Is there any way around it? I read several good reviews on the JJ's, and although they were good, they didn't describe them as having the sound I was looking for. I am not looking for a change just for the sake of changing, but if they will get the sound I want, I'm all for it. Do they get that sound (see first post)?

    Dustin
     
  15. Guinness Lad

    Guinness Lad Silver Supporting Member

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    The tube you want for upper midrange is the cheap and good EH12ax7. They have a lot of low end definition and the frequency of the mids is more towards the upper end of the midrange curve. It really adds alot of presence and clarity to a murky amp and having played a dual rectifier before I have agood idea of what your trying to do. I put a EH in my Guytron and it works great for the clean channel. I wouldn't recommend these in the gain channel becaus ethey can be a bit bright. Also the regular JJ's (short plates) will work in high gain amps but Eurotubes doesn't recommend their long plate tubes in high gain amps.
     
  16. 59model

    59model Member

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    If your not playing metal, I`d suggest some lower gain tubes. 5751`s are great and will tame some shrillness. My Marshall TSL sounded like a chainsaw when I 1st got it. I put a Philips 12AT7 in V1, and cheap Sovtec 5751`s in V2 and V3. Sounds like a good older Marshall now. You may have to run the preamp higher, but the sound is much improved IMO. Good luck!
     

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