Cancel those accordion lessons! (Sorry grandma!) You won't be able to let go of your guitar when you hear the pro level tone and added features of the amazing NEW and easy-to-do Mercury Upgrade Kit.

You can turn your "Tiny Terror" into the tricked-out "HOLY TERROR" with the help of Mercury iron and a few cool Alan Cyr circuit tweaks.

It's our simplest Upgrade Kit, yet. All you (or your amp tech) do is swap the transformers and make a few minor circuit mods. The kit also includes an optional Pentode/Triode mode selector switch that more than doubles the tonal possibilities!

What do you get? Oh man, it's H-U-G-E!!!! Orange attitude 'till it's busting at the seams. Throw away the straw because this is true big gulp overdrive with your Orange drink!

Our "HOLY TERROR" Upgrade Kit features custom-tuned performance Axiom series transformers. The same or higher quality as those used in boutique amps costing substantially more. After you hear the improvement you'll never settle for stock transformers again. The improvement in tone is beyond dramatic. Remember, more than any other component, your amp's transformers determine its tone.

Check out these YouTube demos of the "Holy Terror" by Bob McGilpin of
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LA Amp Show discussion of the "Holy Terror" project.


"Did this Upgrade make a difference? Big time!" -- Ev Southwick

"This thing was simply unbelievable at band practice on Saturday. It was like the amp used to project in black and white and now projects in color. The tones are complex and thick; they were never thin or weedy at all. This little box not only sounded great in the mix, it owned the mix. Especially noticeable when soloing. I went from Gilmour to Van Halen to Billy F Gibbons and was in heaven the entire rehearsal. My band mates were looking at this little white box and just shaking their heads at the TONE! They didn’t know why it sounded good, but man they felt it. It is now one of the BEST amps I own. You have made me one very happy guitar player." -- Brian Hilty


The "McMod" by Bob McGilpin

LogoWhat's that odd little transformer doing on the chassis? That's a Mercury Mini-Choke. Think of it as a shock absorber for your amp's power. And the Mini-Choke delivers a big affect on the overall tone of your amp! Mini-Chokes come in different values so that you can select the tone you like best. Bob McGilpin of in Nashville, made the modification and along with this YouTube video also supplied instructions to show you how to do it (now included in the "Holy Terror" Upgrade Kit manual). We're listing it as an option with Bob's recommended part -- or for a few bucks more you can get one of our MultiChokes that'll let you to dial in the ideal choke setting for your amp.

Attention existing Kit owners: If you already own the "Holy Terror" Upgrade Kit, give us a call. We'll send you the instructions on CD-ROM and the Mini-Choke or MultiChoke of your choice for only the cost of the part!


How about a MultiChoke?

Taking the addition of a Mini-Choke one step further these photos show a "Holy Terror" Upgrade with one of Mercury's new MultiChokes installed. The MultiChoke was invented by Mercury engineers to allow amp techs (and savvy amp builders) to easily sample different choke values before selecting the best-sounding choke to install.

The MultiChoke shown in these photos allows for five different Henry values (1, 3, 5, 7 and 9) to be tested. But Mercury also makes other variations, depending upon your need. And we're beginning to see amps that utilize our MultiChokes with rotary switches that allow the values to be changes on the fly! Very cool! We also built a rotary switch demo for the LA Amp Show (see below).

The MultiChoke is installed following the Upgrade Kit manual's supplemental instructions for the "McMod." The only difference is that you must solder a lead from one of the marked MultiChoke terminal values. You can then easily resolder to each subsequent terminal to test the amp until you've found the optimum sound for your amp. It's really easy to do, and will provide you with extremely informative and usable results. Tweakers love the MultiChoke because it allows them to easily find the right tone for their playing style.

The MultiChoke is sold as a option to the Upgrade Kit (see pricing below), it's inexpensive and you'll be blown away by the results.

As a special demonstration project for the LA Amp Show, we built this MultiChoke version of the "Holy Terror" with a rotary switch that allowed all 5 Henry settings -- plus the original resistor from the "Tiny Terror." The tone shifts subtly at each setting, but the most radical tonal improvement occurs with the original resistor pitted against the 9 Henry setting. Indicating that a 9 Henry Mini-Choke is the best way to go.

Call Mercury now to order your "HOLY TERROR" Upgrade Kit -- or for an authorized Mercury installer near you.

To order call Patrick Selfridge at (818) 998-7791!

AxiomŽ Upgrade Kit for the Orange "Tiny Terror"



    HOLY TERROR Upgrade Kit for the Orange "Tiny Terror" head or combo!
TT-KIT Complete Mercury Upgrade Kit including custom-designed transformers,
components & full color "How to" instructions.

Mercury Mini-Choke or MultiChoke is sold separately.

MM-9H-CH 9 Henry Mini-Choke for Bob McGilipin's "McMod"
(compliments the "Holy Terror" upgrade)

Full instructions are now included with the Upgrade Kit's manual.



(Plus Shipping & handling)

Choose your option:


(Plus Shipping & handling)

Choose your option:


For countries other than the U.S.A. or multiple cords
please email or call
Mercury Magnetics at
(818) 998-7791.


  • This is a specially developed and priced kit. At this time we are not selling the components individually.

  • All kits sold in North America are available in 120V only. At this time non-North American versions are not available.

*NOTE: Mercury's Upgrade Kit does not include the amplifier -- only the components necessary for the Upgrade of an existing amp.

A very special thank you to Bob McGilpin of MV Amps ( for his contributions to this project. Bob, who is not an employee of Mercury, undertook the creation of various A/B demos for this Upgrade Kit and others.

Also see the Mercury Upgrade Kits for the Epiphone Valve Jr., Fender Champ "600," VOX AC4tv and the Blackheart "Little Giant" series amps.

This project and its documentation is the result of technical investigations made by the engineering staff of Mercury Magnetics. The disclosure of the information herein may pertain to proprietary rights, and the furnishing of these documents does not constitute an expressed or implied license to use such materials. Mercury reserves the right to make changes to the Orange "Holy Terror" kit or its components without notice, at any time.

For more information, assistance, quotes or inquiries:

10050 Remmet Ave. • Chatsworth, CA 91311
FAX (818) 998-7835


(818) 998-7791