Custom MojoVibe Reverb Amp *Porn*

Discussion in 'Amps and Cabs' started by TubeAmpNut, Feb 20, 2006.

  1. TubeAmpNut

    TubeAmpNut Member

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    Hi TGP'ers,

    I thought I'd share my latest creation with you. Never a fan of the 'kit' and always wanting to add a little mojo to classic circuits, I constructed this beauty. The basic goal was a kick ass Fender Super Reverb with a little secret sauce. I started with the 'normal' channel of the Super Reverb amp.

    Mission 1: Reverb. I always thought reverb sounded best before the preamp. So I set out to build an integrated 6G15 style reverb inside my amp. I also fixed and redesigned a couple changes to improve the useful range of the circuit. The first was to wire the 6K6 in pseudo-triode mode to open the stage up and reduce sensitivity. I also cut the plate loads down and ran the gain stages hotter (notice the 3W 470R cathode resistor).

    Mission 2: Proper grounding and decoupling. Typical grounding in Fender style amps just sucks. The doghouse is terrible. I wanted a proper ground buss with filter caps decoupled at the gain stage.

    Mission 3: Tremelo. Bias vary 6G16. Doesn't get any better for me.

    Mission 4: Mojo. Who knows what this is? So i gambled in to the capacitor controversy an used Russian PIO's in the signal path. I also wanted a pull boost (on the volume knob) and a special pull mojo knob which adds a little compression and 'hair' for a swampy vibe.

    The result?

    The BK MojoVibe reverb amp. sound clips to follow. Sorry for the huge pics.

    [​IMG]

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  2. pfrischmann

    pfrischmann Member

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    Too Cool,
    I gotta hear this. really great work....All teflon coated wire?
     
  3. Chiba

    Chiba Gold Supporting Member

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    Very cool, can't wait to hear it! I like that you used 2 different colors for your heater wires, a lot of amps I see use the same colors and I find it confusing a little.

    --chiba
     
  4. TaronKeim

    TaronKeim Member

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    I agree with everything said so far... great looking wiring job too... is the Mojo knob like the "raw" control on some amps? and what exactly does the pull Mojo do? Is it a gain boost? Awesome job man:)

    -TJK
     
  5. TubeAmpNut

    TubeAmpNut Member

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    Thanks,

    The wiring is all solid core telfon. Solid core is the only way to go to keep the bends in place.

    The pull boost bypasses the tonestack. Instead of lifting the middle pot (which would have been a 'pull normal'), I added a big 7n cap in parallel with the treble cap. This gives a flat response (or a 10dB mid boost, depending how you look at it).

    The mojo is secret :). But it's really just a little circuit to add an asymmetric bound with a variable compliance (10k pot). It's out of the circuit untill you pull the knob. It add's hair and compression, but it's very subtle. You can hear it when playing hard full chords. I'll have clips in a couple days.

    BK
     
  6. goose

    goose Guest

    Very nice and clean work! Congratulations! Have you solved cabinet and speaker stuff yet? Also Super Reverb -style?
     
  7. r9player

    r9player Silver Supporting Member

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    Looks great, can't wait to hear it!
     
  8. Leonc

    Leonc Wild Gear Hearder Gold Supporting Member

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    BK Amps - Very clean looking work, man!!

    [moderatorHat=On]Do you make amps like this for sale? If so, this thread belongs in the dealer emporium. Let me know and I'll move it for you[/moderatorHat]
     
  9. DocRock

    DocRock Supporting Member

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    I'd love to hear it...looks like it kicks major ass!!!
     
  10. TubeAmpNut

    TubeAmpNut Member

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    Yup. Vibroverb style with a 15" Legend.

    ...I'm not too crazy about the faceplate. It looked better on paper (I might pop some Fender cream style knobs on it). The 'level' label on the reverb side needs to read 'tone'.

    BK

    [​IMG]
     
  11. r9player

    r9player Silver Supporting Member

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    +1 on changing to "chicken head" knobs
     
  12. pfrischmann

    pfrischmann Member

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    Clips ready yet??


    BTW, I don't know if the cab would allow this but I'd bet a 15 and a 10 or better yet 1-15 and 2-10's would kill.

    FWIW,
    I'm not too jazzed about the styling either.
     
  13. Blueser

    Blueser Member

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    Yes...Clippage is required! I would go with the cream chicken heads as well, and ditch the silver sparkle grillcloth for something like a cream tolex, or wicker! It would be a nice off-set with the black.
     
  14. r9player

    r9player Silver Supporting Member

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    but changing the grill cloth might damage the baffle ... isn't this the classic Fender look?
     
  15. pfrischmann

    pfrischmann Member

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    I agree with blueser. It just needs a little bit of eye candy.......You know what else might be cool a way to toggle between putting the verb either before the pre, like a stand alone unit ....or the ability to put it where a BF usually is......Why?

    Having it first is cool but if you like doing the SRV thing with a tube screamer, the sound gets very squished when it hits the verb unit first and can lose some punch. You can really feel it compress.

    FWIW.

    Oh yeah.....clips?
     
  16. pfrischmann

    pfrischmann Member

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    BTW,
    I don't know if a lot of people are doing the cream/oxblood look these days...that's always a good look....maybe with a different color face plate so you can identify it from the end of a stage.....
     
  17. TubeAmpNut

    TubeAmpNut Member

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    Okay, here is a clip.


    http://www.ariatech.net/MojoVibe/clips/MojoVibe1.mp3

    This clip starts with both Reverb and Mojo engaged. You can notice a slight increase in harmonics. I then replay a similar riff with the Mojo knob pushed in (you can hear it click). This has smoother tone but higher headroom. I then roll in some tremelo then grab the mix knob and rotate the reverb about 50% wet.

    BK
     
  18. pfrischmann

    pfrischmann Member

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