Does Anyone Use Preamp Tubes Other than 12AX7 Type?

Discussion in 'Let's Talk Vintage' started by matttornado, Sep 4, 2020.

  1. matttornado

    matttornado Well-Known Member

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    I have an old 70's Super lead that is a gain monster, even on modest volume settings.


    Lately, I' been working on getting my Russian Big Muff to work with this amp and it has been very challenging to say the least but I'm finally there with single coil pickups, amp volumes set less than half way & and an Overdrive pushing the big muff to EQ the sound so it's not muffledbut cuts through.

    I just put, I think, a 12AY7? in V1 to tame this amp a little so the Big Muff has room to breathe so to speak. It seemed to help a little.

    So If I put say a 12AU7 in all three pre-amp slots, what would the amp sound like, a clean Fender sort of?

    Bottom line is that I'm trying to clean this amp up so it's more distortion pedal friendly.
    I played this amp cranked on 10 with various attenuators & no drive pedals for half my life & I want to go a different route. I like having to step on a pedal for distortion / FUZZ istead of the cranked Marshall sound. Tired of it.

    Anyone else try lower gain pr-amp tubes in there Super Leads?
     
  2. pedecamp

    pedecamp Well-Known Member

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    Unless the amp has been modded, I'm surprised to hear you cant put the volume on 2 or 3 which would be blazing loud but clean, then stomp a pedal for gain. Maybe a life time ago you had a gain mod added to the amp and you dont remember? Maybe have a tech check to see if the amp is stock or not and put it back to stock if thats the case. :yesway:
     
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  3. IOSEPHVS

    IOSEPHVS Well-Known Member

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    You might want to try a Mullard CV4004 for V101. It's a special version of the 12AX7. I use four of them in my amp. They test about 20% higher (micromhos) than Mullard 12AX7s. Lots of headroom, and the clean channel in my Marshall never sounded so good.
     
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  4. rjohns1

    rjohns1 Well-Known Member

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    I really like the JJ ecc83MG tubes in v2 and v3 of my 40CR.
     
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  5. South Park

    South Park Well-Known Member

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    Using the 12au7 in all tube sockets you might not get the right tone. But try it to see . You don’t get a name like that for nothing.
     
  6. Amadeus91

    Amadeus91 Well-Known Member

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    [​IMG]
     
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  7. AlvisX

    AlvisX Well-Known Member

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    In my guitar specific amps ,especially the cascade preamp ones, I'll likely use a 5751
    I like 12Ay7 in my harmonica amp and 12au7 or 12ay7 for bass ...to clean up the farties
    !2at7 is a great phase inverter
     
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  8. Filipe Soares

    Filipe Soares Well-Known Member

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    I'm using a 5751 as V1 in my 5150III
     
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  9. matttornado

    matttornado Well-Known Member

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    thanks for the replies. i guess i’ll have to experiment a little more.
    BTW: my amp is a stock superlead circuit except i added a ppimv.
     
  10. matttornado

    matttornado Well-Known Member

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    it’s mostly stock. i made a few minor component value changes , added a cap, and changed it to use el34s.
    i been this amps tech for 20 years and must have tried every mod under the sun. now it’s mostly stock. go figure.
    amp sounds cranked on 2. always have always will.
    been down that rabbit hole trying to find out why.....,
     
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  11. MarshallDog

    MarshallDog Well-Known Member Gold Supporting Member

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    I have experimented BUT always end up back to stock 12ax7 types. Just sounds better over all to me.
     
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  12. South Park

    South Park Well-Known Member

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    The 12ax7 works because the preamp is designed that way . Audio circuits are designed to be leaner . The power curve is a straight line in all tubes . When you mismatch the tubes it is not the same . You have tone caps rolling off frequencies at different power levels . So if you want to make this work you need a slide ruler
     
  13. Trapland

    Trapland Well-Known Member

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    Consider moving the negative feedback wire to a different tap. Or changing the NFB resistor to a lower value. This should give you much more volume before distortion and will take Your pedal better.
     
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  14. matttornado

    matttornado Well-Known Member

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    I have a 27k NFB R on the speaker tap along with my ppimv.
    that does help a lot.
     
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  15. matttornado

    matttornado Well-Known Member

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    thanks for all the replies!
     
  16. neikeel

    neikeel Well-Known Member

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    Using CV4004 (M8137) or 5751 across the preamp will probably work well. NFB 27k/16 helps (presume 16 ohm cabs?).
    There are ways to clean your preamp up but it depends what your ‘stock’ spec is at the moment. (Hint : pics please!)
     
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  17. Jim Jones

    Jim Jones New Member

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    Does yours have a 5000pF bright cap on the Bright channel volume? If so that basically turns the volume into an On-Off switch. 100pF-500pF works better there for me.

     
  18. matttornado

    matttornado Well-Known Member

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    That was first thing I tried many years ago!;) thanks for the suggestion though.
    I took that cap off and left it off 20 years ago.
     
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  19. matttornado

    matttornado Well-Known Member

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    I don't have a pic at the moment but here are the specs all done by me:

    1974 Metal Panel 1959 Super Lead:

    - no bright cap on volume 1 (5000pF cap removed)
    - 0.022 uF orange drop on V1B (changed from a 0.0022uF original spec.)
    - added 0.68uF orange drop cap on V2A (like plexi's had)
    - LAR -MAR PPIMV added
    - NF 27K / speaker jack (originally was a 100K to 4 ohm tap)
    - converted to EL34s
    - presence control changed to 0.1 uF plexi spec.
     
  20. Jim Jones

    Jim Jones New Member

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    Removing the .68 cathode bypass cap will help the cause.
     

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