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Xotic AC Booster- What is it?

Discussion in 'The Stomp Box' started by TelZilla, Mar 24, 2020.

  1. TelZilla

    TelZilla Friend of Leo's

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    So I'm generally of the belief that most pedals are largely based on pre-existing designs. I'm wondering about the Xotic AC Booster.

    I've heard it's a modified tubescreamer, that it's supposed to sound Voxy (I guess because of the "AC").

    Your thoughts?
     
  2. Peegoo

    Peegoo Poster Extraordinaire

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    It is a boost with EQ that adds a wee bit of dirt, hence the AC ("almost clean") name.

    Their RC Booster is "real clean."
     
    Fretting out likes this.
  3. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    It's a modified Tubescreamer.
     
  4. Electric Mud

    Electric Mud Tele-Holic

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    Check out the Earthquake Devices Plumes. Different take on tube screamer. 3 voicings. Boost to low & mid overdrive. $99! Made in Ohio.

    Sent from my VS988 using Tapatalk
     
  5. don71

    don71 Tele-Afflicted

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    I'm still learning about all the differences in booster pedals. I watched this video just yesterday and it might help. Its a little nerdy and I like that. I don't think the ac is talked about, but he does touch on the EQ differences and what kind of parts drive them to their different sounds.



     
  6. TelZilla

    TelZilla Friend of Leo's

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    As ever, TDPRI speaks with one voice.
     
  7. don71

    don71 Tele-Afflicted

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    Have a great day.

    [​IMG]
     
  8. Thinline casket

    Thinline casket Tele-Meister

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    The super sweet is also a modified tube screamer, which sounds nothing like a tube screamer. Lol

    It has DIP switches on the outside. Very useful! (It's also a mad professor clone.)
     
  9. TelZilla

    TelZilla Friend of Leo's

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    I wouldn’t have it any other way.
     
  10. scooteraz

    scooteraz Friend of Leo's

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    The day that happens will be the end of the world as we know it. LOL
     
  11. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

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    The AC and the BB show up on a lot of pro boards. For that reason alone, I've thought about giving the BB a try.
     
  12. beninma

    beninma Friend of Leo's

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    I haven't heard it in a long time.. but my guitar teacher had an AC booster and used it with his vintage Princeton with a Tele... the EQ on the AC definitely suited the Princeton, probably safe to assume it suits a lot of Fender amps for light dirt sounds.

    All that said I am really of the opinion that straight up boosts are better for amps that get dirty more easily. Dirtier drive pedals are by contrast more suited to amps that have a lot of headroom and try harder to stay clean.
     
  13. 11 Gauge

    11 Gauge Doctor of Teleocity

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    The AC is a combo of circuit stuff that's at least partly derived from something TS-like, although I think the clipping diodes used are pretty much SD-1-like. Even though it's true bypass, Xotic also kept the input and output buffers like the TS/SD-1 have.

    The tone circuit that you'd find in a TS/SD-1 is basically hardwired in the AC (IIRC). It then has what's called a Baxandall tone circuit, for active bass and treble. Long story short is the mid voicing is basically hardwired in.

    So the AC Booster isn't really a booster at all, it's a bonafide OD, IMO.

    Also, the AC and RC are built on the same circuitboard, with the RC having less than a dozen component differences - obviously operates in a lower gain range, has different clipping diodes to make the clipping more subtle, isn't voiced for much (or any) midrange emphasis.
     
  14. TelZilla

    TelZilla Friend of Leo's

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    This makes sense to me. I see a couple chips on the schematic, and it's got a gain knob, in any case. It's obviously no Metalzone, but the border between boost and low gain OD is mostly mental anyway, depending on whether you're using a Champ or a Twin. Well, I've got one on the way, so I can soon form my own opinions.

    Thanks all for the input and thoughts. This really is a great (virtual) place.
     
  15. schenkadere

    schenkadere Friend of Leo's

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    The AC does seem like a bonafide OD. The RC is the most useful boost I've ever had. Granted, I have a clone, but the circuit just does the trick for me. Adds some magic to a dirty amp. I set it for a touch more grit, cut the bass and treble just a bit, and volume at 3 o'clock. Wonderful things happen.
     
  16. telerocker1988

    telerocker1988 Tele-Afflicted

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    What about the BB? Is it on the same board too and how is it different from the AC?
     
  17. 11 Gauge

    11 Gauge Doctor of Teleocity

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    Actually, I went back and looked at the schematics of all three (apologies that I tried to recall the schems from memory, for my prior response).

    Basically, the AC shouldn't really have a ton of mid emphasis. And then the RC will have an even flatter response, with lower gain, and even less clipping.

    It's the BB that's a bit different, and does have a different board, yes...
    • The primary gain stage in the BB is a chapter-and-verse TS circuit, except that it subs out a 1 meg gain pot in place of the TS's 500K
    • On the output of that gain stage, the same hardwired filter as in the TS, that rolls off everything above ~700Hz - that's verbatim, too
    • Next up is basically the equivalent of a hardwired TS tone circuit, and other than the omission of an adjustable 20K pot, that's all chapter-and-verse TS tone circuitry, too. There's a voltage divider pair of resistors - 1K / 19K, that are substituted for the TS's tone pot
    • Then it basically hits the exact same Baxandall treble and bass tone circuitry as you'll find in the AC and RC
    ...Also, it's getting into the tech weeds a bit, but the AC/RC have the primary gain/clipping stages with the signal fed thru what's called the inverting input only. When done this way (e.g. 'not TS-like'), you don't get the effect of blending signals at the two inputs (inverting and non-inverting, which mixes a unity gain with a clipped signal) like a TS and the BB will do, which part of what gives the specific 'magic' of TS types of ODs. As far as what that translates to, for what you end up hearing, I can really only suggest comparing them. You may prefer one over the other.
     
  18. telerocker1988

    telerocker1988 Tele-Afflicted

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    Thanks!

    I have all three original pedals (RC, AC, and BB). I find them to all do their own thing well, but I find myself coming back to the BB mostly, especially next to the AC. I do favor the TS types, so it's no surprise really. I think the BB is definitely it's own thing. The RC to me is just a AC with less gain on the pot and more for clean boostage. I think as an overdrive, the BB surpasses the AC, at least for me. I think the BB is a really cool pedal. I bought all 3 at Rock Block in Nashville years ago. The BB is on the board the most.
     
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