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which 12AX7 for RIVERA amp?

Discussion in 'Amp Central Station' started by telegumbo, Nov 17, 2013.

  1. telegumbo

    telegumbo TDPRI Member

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    hi, i have a rivera amp (2xEL34 and 5x12AX7) and currently it holds the cheapest tubes you can propably find in this galaxy.
    now its time to replace the 12ax7 tubes (there is some rattling going on).

    right now it sounds rather british (which is basicially ok) but with harsh annoying heights. so overall i want to smoothen the heights and propably get a warmer and creamier overall sound.

    do you have any suggestions for 12AX7 replacement tubes?
    ist there anything among the current models that should be avoided or something that almost always sounds fine?

    thanks
     
  2. bun malaey

    bun malaey Tele-Afflicted

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    My amp tech swears by JJ tubes.
     
  3. telegumbo

    telegumbo TDPRI Member

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    ok, i could get three variations, do you think there are any noticeable differences in sound?

    JJ ECC83S
    JJ ECC83S Gold pins
    JJ ECC803S
     
  4. DaveKS

    DaveKS Friend of Leo's

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    TAD 7025 in v1-2, JJ 803 plain pins rest. Avoid reg jj83's, dull, lifeless sounding tubes IMHO.

    If you really wanna tame that high end though, go to KCA tubes and pick up a RFT for $60 for v1, then follow it with tad and JJ 803.

    EDIT: just noticed your in Germany, you should be able to pick up the RFT and some Amperex pretty cheap.
     
  5. telegumbo

    telegumbo TDPRI Member

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    Thanks. I'll first buy a set of JJ803 then and later try some others in V1.
    I have two old tubes laying around (Telefunken and Lorenz) - but I dont know if they are still good.
     
  6. uriah1

    uriah1 Telefied Gold Supporter

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    Dont like JJ for preamp tubes..mostly for power tubes.

    New stuff ; Tung sol and sovtek
     
  7. telegumbo

    telegumbo TDPRI Member

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    ok, and which sovtek do you like?

    i could get

    12AX7 EH
    12AX7 WA
    12AX7 WB
     
  8. mitchfit

    mitchfit Tele-Holic

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    ..."but with harsh annoying heights. so overall i want to smoothen the heights and propably get a warmer and creamier overall sound. "...

    just want to make sure i understand your question:

    when you say "heights" do you mean distortion/clipping/crunch, or treble/high frequency?

    if it means treble, there will be very little change for that from different pre-amp tubes.
    try different pick up combinations, the guitar tone knob or an EQ pedal in front of the amp.

    if you mean "distortion/clipping/crunch", try lower value 12__7 tubes in the pre-amp circuit.

    highest output, or "gain" is 12AX7 @ 100.
    5751 is next lowest @ 70.
    12AT7 is 60.
    12AY7 is 44.

    likely any lower gain values will kill too much volume. the 12AY7 may sound kind off dull, depending on your circuit. may not work well for the PI tube either.

    start off trying just 5751 an 12AT7 in V1 and the phase inverter socket, (PI). try both in both positions to see if they do what you want acheived.

    the phase inverter will most likely be the last 12__7 hole from the input jack. or the 5th one, nearest the output transformer. check a schematic to be sure.

    if those two alone don't clean it up to your tastes, then start substituting V2, V3 and V4 with lower gain tubes. they will likely be for the high gain circuit, if it is a two channel pre amp. 12DW7 works good for taming a too crunchy lead/high gain cascading channel being a 12AX7 on one side (100), and a 12AU7 (20) feeding the next tube.

    you will need to determine if V2 is also in the clean channel circuit to decide about where a 12DW7 would help.

    mitchfit
     
  9. telegumbo

    telegumbo TDPRI Member

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    i meant harsh sounding high frequency tones.
    when playing high notes (also as part of a chord) the exact moment you touch a string it sounds immediately earpiercing.
    it feels rather digital (on or off) - and the inbetween is missing.
    tried different guitars and pickups and although it has has two channels (each with a boost option) and one million knobs, i never got it as smooth and mellow as my other (cheaper) amps.

    i want to change all the preamp tubes - because one of them is rattling and the rest i want to change at least for spiritual reasons.
    the ones that are in now have nothing written on them except "made in china".


    It is powered by two EL34 and i always have plenty of headroom, so it shouldnt matter.
    Thanks for your suggestions. Ill try the other tube types if the new 12AX7s wont make any difference.
     
  10. DaveKS

    DaveKS Friend of Leo's

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    Well Telefunken last forever and make one of the best v2 around. The Lorenz I have tried and are very nice, try them, you might be surprised.
     
  11. krisls

    krisls Tele-Holic

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    I have an R55112 and my amp guy recommended EH all through. They've been in for a few years and are clean and smooth. No harsh sounds and I can go from Marshall to Fender with channel and EQ tweaks.

    Kristina
     
  12. soulman969

    soulman969 Telefied Ad Free Member

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    This will probably help you out a great deal. AES compares 12ax7 tubes and their characteristics from all of the major suppliers of new tubes.

    http://www.tubesandmore.com/tech_corner/12ax7_comparison_of_current_made_tubes

    I like JJ power tubes but personally I wouldn't use JJ preamp tubes. The quietest running and best balanced I found were Tung-Sols followed by Electro-Harmonix but the Tung-Sol would be my first choice.
     
  13. flyswatter

    flyswatter Friend of Leo's

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    +1 on the JJs. I just redid my Rivera-era Super Reverb in all JJs (12AX7s and 6L6s) to replace older 7025s and they do the job perfectly. They're inexpensive and easy to find... and the tone of my amp lost nothing by replaceing old vintage classics with new production JJs.
     
  14. mitchfit

    mitchfit Tele-Holic

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    ..."i meant harsh sounding high frequency tones."...

    if you use any dropped tunings, a 10 band EQ would be in order.
    if not, many cheaper units are out there, check the user's reviews:

    http://www.musiciansfriend.com/sear...profileCountryCode=US&profileCurrencyCode=USD

    other than that, changing speakers or modifying the pre-amp
    circuit gets more expensive, and will be harder to reverse if
    you are not happy than just discontinuing use of the EQ.

    $0.02
    mitchfit
     
    Last edited: Nov 19, 2013
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