Help! Groove Tubes 12ax7s in a Rivera M60

Discussion in 'Amps and Cabs' started by JingleJungle, Apr 20, 2005.

  1. JingleJungle

    JingleJungle Member

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    Hi y'all...
    Since my Rivera M60 was starting to make funny scratching noises I splurged and purchased a set of GT 12ax7m tubes (someone says they're Mullard clones...go guess)
    .
    Now I have no noises (at least one problem is solved) - but overall the sound has become much warmer (read: darker, bassier, whatever).
    I really wasn't expecting this.

    What brand / type of pre tubes should I choose for an "airier" (i.e. less dark) sound?

    Last Q: what can I do to test the pre-existing pre-tubes? I suspect that only one of them was gone, but how can I test this assumption in a scientific manner?

    Thank you...

    JJ
     
  2. hipfan

    hipfan Member

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    I recently shifted the V1 and V2 pre-amp tubes in a Rivera Fandango from the 12ax7M's to the new JJ ECC803S's. *Much* airier and more open than the 12ax7M's. Very nice tone so far. I got them from Doug's Tubes. I think they cost $12 each or so.

    As for checking for bad pre-amp tubes, you can try tapping each one with a chopstick lightly while the amp is fired up at low volume. If you get some strange noises, then the tube could be bad.

    If that doesn't work, try replacing them one-by-one with known good tubes and see if there is any improvement. Don't replace them all at once.
     
  3. haslar

    haslar Member

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    Rivera pre-amp tube issues have been thoroughly discussed on this forum already.
    The "search" function might come in handy.

    This being said, as an M60 owner, I have figured out that the best preamp tubes to use seem to be chinese tubes.
    It seems NOS are not the best choice including Mullards.
    Golden Dragon tubes do wonder in those amps.
    Rivera amps seem to be dark-ish amps, they match well with bright tubes.

    However, I do use a 12AX7GT Mullard RI in V2, which helps channel 1 a lot in obtaining that classic Marshall grind.

    YMMV.
    :)
     
  4. Jimmydeez

    Jimmydeez Supporting Member

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  5. riverastoasters

    riverastoasters Member

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    Getting really dark can happen with some types of preamp tubes in Riveras. Groove tubes in all positions can do this. Try sticking a Chinese 12AX7 in a place or two.

    Here is a link to some more info:

    http://bellsouthpwp.net/r/i/ricjohns/Rivera Preamp Tube Guide.htm
     
  6. dazco

    dazco Member

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    It strikes me odd that you want an "airier" sound than the M's....i find them to be the airiest 12ax7 i have ever used by a mile. But then again now that i think of it, they didn't sound all that airy or even necassarily very good in another amp i tried them in. Guess they're very amp dependant. But in my C30 they are incredibly airy, or maybe a better description yet would be "transparent".
     
  7. JingleJungle

    JingleJungle Member

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    Awesome link, thank you.
    And thank you all for your kind input (no pun intended).
    Now I have to go and have a word with a friend of mine - an electronics specialist - who insists tha tubes don't "sound", because "all they do is increase the voltage".
    My @ss....LOL

    JJ
     
  8. Greggy

    Greggy Member

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    I own an M60 and have read all the web based advice. Here's what I ended up using as the best balance between the fender and marshall sides of this amp:

    v1=EH12ax7
    v2=Brimar cv4004
    v3=chinese r9
    v4=chinese r9
    v5=sovtek 12ax7LPS

    This is just bright enough to make the fender side chime and dark enough to make the marshall side distort without raspy high end.

    BTW, this is one great amp, built to last.
     
  9. haslar

    haslar Member

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    Greggy,

    here is mine:
    V1: EH 12AX7, or chinese
    V2: Groove Tubes Mullard RI 12AX7
    V3: Watford Valves Harma STR 12AX7
    V4: Golden Dragon 12AX7A
    V5: Mullard CV4024 (12AT7 equivalent)


    Very close to yours, it seems... :)
     
  10. JingleJungle

    JingleJungle Member

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    My MASS attenuator is te culprit.
    Basically IMHO since the loudspeaker is really built for much higher power loads - and is naturally "darkish" sounding - when I attenuate to room levels the cone doesn't get enough juice to reproduce the higher freqs (pls correct me if I'm wrong).

    I tried my amp at full blast today - and boy, does it sound SWEET!!!!

    I'll just have to dial a way different EQ setting for bedroom use to compensate for Fletcher-Munson and for the darker sounding cone... or else build a small 2x10" box with lo-wattage spkrs.

    There ya' go.

    Thank you all for your precious input AND for the great link!!!!

    JJ
     
  11. riverastoasters

    riverastoasters Member

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    I have come across people that don't exactly dig that box. I use Hotplates pretty successfully. But still, if you attenuate down to conversational volume you usually have a tonal compromise. One trick with the Hotplate is that you can run it as a load, and take the line out into a solid state (e.g. PA) amplifier and eq that. That gives really good tone at any volume. Of course, you need the clean amp as well.
     
  12. JingleJungle

    JingleJungle Member

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    Weeeelll....
    Tell ya' the truth - at least the MASS doesn't produce any "buzzy" sounding crunch or distortion when the attenuation is realtively high.
    The compromises sofar are more than acceptable and I don't have any of the reported side-efffects that seem to plague hotplate users (raspy sounds at low volumes, etc) - but this is stuff for another thread :)

    A friend of mine has a cab with a lo-wattage Jensen speaker... we'll get together soon to try it out with my Rivera.
    I'm curious...

    JJ
     

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