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Thread: Ampeg V4 Reverb tank removal.. a weird request

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    Ampeg V4 Reverb tank removal.. a weird request

    Hey folks, a client brought me a 70s ampeg V4 with a laundry list of issues which have all been taken care of. He would like the Reverb tank removed since he does not use it.. I tried to convince him to keep it in there but he really wants this..

    I need to replace the tank with some kind of load, correct? Im not positive of the exact impedance of the tank but wondering if anyone else has done this or has tips? Thank you!

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    Lifetime Member Enzo's Avatar
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    Unplug it and move on with your life. The pan is driven off a tube plate via a cap, forget impedances and loads.

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    Education is what you're left with after you have forgotten what you have learned.

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    Don't forget the joker g1's Avatar
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    ^^^ What he said.
    It's a high impedance tank and the driver tube will still be loaded by it's plate resistor.
    You can permanently engage or hardwire the footswitch jack so the return circuit doesn't add any noise, but that would only happen if the reverb pot was turned up.
    Some might suggest removing the driver tube but I would not want to risk any increase in the already very high B+ in these amps.

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    Just because they don't have tubes doesn't mean they don't have feelings! - glebert

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    Senior Member SoulFetish's Avatar
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    maybe this goes without saying, but I would remove the RCA cables from inside the chassis. Or, tie them off so that there is no risk of the plugs contacting any other part of the circuit. The reverb input is capacitively couple (as mentioned above), but when unloaded, the capacitor charges to a high voltage and the RCA plug can give someone a bit of a shock. So, if you were inclined, you could put a shorting cap on the plug, or solder an 82k resistor in parallel with the reverb input side of the capacitor. This really has no effect on the reverb performance, so you can just leave the resistor in circuit if the customer decides they want reverb again.

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    I removed the tank in my V4 many years ago

    I wrapped the reverb RCA plugs in a plastic bag held on with twist ties so they can flop around to their hearts desire without causing a shorting problem.

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    Thanks everyone!

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    Old Timer J M Fahey's Avatar
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    There was a famous Russian Orthodox sect, the Skoptsy, who swore eternal celibacy, so no reproduction or kids in their life, so they castrated men and practiced mastectomy on women because they had no use for those parts anyway.
    https://en.wikipedia.org/wiki/Skoptsy
    Maybe they also avoided a lot of noise in their life

    Not just "a couple crazy guys" , they reached a peak of 100000 members in the early 20th Century.

    Oooops, maybe "members" is what was actually missing there

    Back to Electronics, I guess shorting the return jack (and leaving Reverb there) will actually be more silent than plain removing the tank.
    Just sayin'

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    Juan Manuel Fahey

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    Senior Member TimmyP1955's Avatar
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    Have some fun and experiment: With some amps, if you connect the reverb send and return, the reverb circuit makes a fun parallel hi-gain stage.

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    Just put a 470k in place of the tank & screw around from there! Noisy as crap, though... But fun anyway. If it's punk rawk, who cares?

    Jusrin

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    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
    "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
    "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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    Old Timer J M Fahey's Avatar
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    Yes, in the early 70s a guy made and sold a device called "the ice cube", literally a couple parallel RCA plugs, probably including a 10 ohm resistor not to blow the reverb drive transformer, encapsulated in black resin.
    And his mold was literally a rubber ice cube tray so he could pull it out afterwards.
    RCA plugs were the proper distance so as to straight plug into Reverb send-return jacks.

    Imagine!!! A FENDER!!! (and a Blackface at that) with *footswitchable DISTORTION!!!!*

    Take that, Marshall!!!

    Maybe they also included a couple clipping diodes, at least to avoid blowing next triode grid with a speaker level signal.

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    Juan Manuel Fahey

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    Senior Member SoulFetish's Avatar
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    Quote Originally Posted by J M Fahey View Post
    Yes, in the early 70s a guy made and sold a device called "the ice cube", literally a couple parallel RCA plugs, probably including a 10 ohm resistor not to blow the reverb drive transformer, encapsulated in black resin.
    And his mold was literally a rubber ice cube tray so he could pull it out afterwards.
    RCA plugs were the proper distance so as to straight plug into Reverb send-return jacks.

    Imagine!!! A FENDER!!! (and a Blackface at that) with *footswitchable DISTORTION!!!!*

    Take that, Marshall!!!

    Maybe they also included a couple clipping diodes, at least to avoid blowing next triode grid with a speaker level signal.
    Not a bad idea. I suppose with an appropriate load on the secondary to take some of the heat, you could also tap signal off the resistor and connect an audio Transformer in parallel to step the voltage up enough to overdrive the next stage. You might be able to still keep the secondary impedance low enough to push the grid a bit into the +V region and get another
    flavor of overdrive. These audio Transformers are cheap and small. (and assumes a fender Transformer coupled reverb driver like mentioned above)

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    If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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    You have to pad the signal down, otherwise it's too hot.

    I experimented with this on a Marshall 2210 I had.

    Eventually what I did was leave the reverb in but increased the gain of the return amp so it was like a solo boost with a bit of reverb
    thus making it a three channel amp!

    Did it to the 1x12 combo version 4210 I had also.

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