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The Mean 18: British-Style 18-Watt Amp Kits from Mojotone and Tube Depot

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Tube Depot Classic British 18W Tube Guitar Amp Kit 1x12

The parts. Tube Depot stocks their kit with quality parts, though they use many modern components. The capacitors match the original values, but in a smaller footprint. The higher-wattage resistors are carbon composite, but most are of modern metal film. The power and output transformers are from ClassicTone. The speaker is a British-voiced Weber 1230. The amp includes a footswitch jack for activating the tremolo, but no switch is included. (Two-speed trem switching is available as an optional mod.) The small parts arrive in dozens of little plastic bags. Tube Depot provides shielding tape, insulation material, and other performance-enhancers rarely included with kits. The modern, PVC-insulated wire comes in multiple colors, which helps clarify things while following the build instructions.

The build. Tube Depot amp kits stand head and shoulders above the competition in one key area: documentation. While other kits offer at most a schematic, a wiring diagram, and a few pages of build guidelines, this one includes a 52-page, full-color assembly manual. It’s one of the clearest and most comprehensive instruction guides I’ve encountered, with every step explained and illustrated. Take it from someone who’s done a lot of guitar-tech writing: These instructions represent an enormous effort on the part of Robert Hull of myamptech.com, who created them for Tube Depot. If you suspect you need detailed, step-by-step guidance to complete a successful build, this one feature may be enough to sway your purchase decision. You can download the docs for free from the Tube Depot site. (Hull also created a YouTube video summarizing the build process.)

This wasn’t my first amp build, but thanks to Hull’s instruction, it was my best. Hull doesn't merely explain what goes where—his guide is chock-full of useful tips covering everything from the most efficient assembly sequence to the fine points of “lead dress” (the fancy term for tidy, efficient wiring that doesn’t look like a rat’s nest). The circuit is intelligently laid out, with most passive components secured to the turret board, and relatively few awkward solder points and wire runs.


The Tube Depot kit employs modern parts, such as metal-film resistors, small-format capacitors, and color-coded, PCV-insulated wire.

For better or worse, though, this is a labor-intensive build. For example, you must assemble your own turret board before mounting the components, as opposed to some other kits, which provide prefab turret board. Here you must tape a template to the fiberglass base plate, drill each turret hole, and then press-fit each turret into place using a hammer and an included tamping tool. If you want to learn new skills and have fun at the workbench, you’ll probably dig the process. (I certainly did!) But if you just want an inexpensive amp in a hurry, you may prefer a kit with more pre-assembled components.

The amp took me two days to build—longer than expected, but mainly due to the fact that I was learning and practicing new build techniques and auditioning the optional mods covered in the documentation. It was time well spent, and when I finally fired up the amp, everything worked perfectly. Believe me—that’s not how things usually go on my workbench!

The results. The Tube Depot 18-watt amp looks great and sounds good. It delivers the expected hallmarks of 18-watt tone: intense overdrive at relatively low levels, lots of treble excitement, and a simple yet singularly effective single-band tone circuit. The response is exceedingly dynamic, cleaning up nicely as you roll back your guitar volume. Typically for an 18-watt, the amp doesn’t exactly move the earth with its lows, though the Weber speaker sounds full and satisfying.

Ratings

Pros:
Peerless assembly manual, including many cool mod options.

Cons:
Some parts might benefit from upgrades.

Tones:

Ease of Use:

Build/Design:

Value:

Street:
$849

Tube Depot Classic British 18W Tube Guitar Amp Kit 1x12
tubedepot.com

I incorporated two suggested mods: a post-phase-invertor master volume control (with a pot replacing one of the four input jacks), and a post-phase-invertor tone-cut circuit pilfered from the Vox AC30 (with a pot replacing one of the speaker out jacks). Both work great: The master volume provides surprisingly good high-gain sounds at low levels, while the tone-cut is tuned just right for nixing nasty overtones when playing at maximum gain. I recommend both mods for any 18-watt build.

The verdict. I had a fantastic experience building both kits—or more accurately, two fantastic but different experiences. Which experience is best for you depends on your DIY motives.

I prefer the Mojotone’s sound. There’s more of a bell-like quality to the clean tones, and when you pour on the gain, everything resonates a bit more sweetly, with fewer harsh and chaotic overtones. It doesn’t emit more low end per se, but the fundamental frequencies seem weightier. I dig this taut, focused character.

This is a subjective call, however, so judge for yourself: I recorded the audio examples for both amps through the same signal chain minutes apart, and even used a ReAmp to route identical performances through both amps. (If you’re reading this in print, check out the online version of this article, which includes audio.) The Royer R-121 ribbon mic is situated in the same position for each amp. I even tried swapping tube sets between amps, and auditioning each amp through the other’s cabinet and speakers, neither of which altered my impressions.

I attribute the sonic differences to internal components—but attempting to pinpoint which component is responsible for what is the sort of thing that launches flame wars on amp sites. Mojotone goes the extra mile to provide their namesake mojo parts, though I’ll remain skeptical that cloth-covered wire, carbon-comp resistors, or large-format caps have perceptible effects on an amp’s tone until I encounter repeatable audio evidence proving it. But most folks agree that transformers affect an amp’s tone in a big way. My hunch is that I simply prefer the sound of the custom Heyboers in the Mojotone to Tube Depot’s ClassicTones. (For what it’s worth, the Mojotone transformers cost twice as much. Conversely, the Weber speaker in the Tube Depot amp costs twice as much as the Mojotone speaker, though I like the sounds of both speakers about equally.) I’d love to hear the Tube Depot kit with upgraded transformers.

Meanwhile, stellar documentation makes the Tube Depot kit the superior learning and building experience. The techniques included here will improve not only your 18-watt build, but also any future amp projects. (They certainly helped me build the Mojotone kit!)

My time with these kits has only deepened my regard for this 49-year-old design. Not many amps impart such a strong sense of time and place. An 18-watt can really make you feel like you’re playing a 1966 London studio session. By all accounts, Eric Clapton used a JTM-45 on his Bluesbreakers session, but to be honest, these 18-watts took me closer to that iconic squawk than most JTM-45s I’ve played. (I’d harbored doubts about Clapton’s claim that he didn’t use a Rangemaster treble booster on those dates for the simple reason that it sounds like a frickin’ Rangemaster! But for the first time, I can imagine how a particularly fiery Marshall combo and lively, unpotted PAF pickups could conspire to produce that tone.)

The 18-watt is no chameleon—it’s a singular circuit with a singular point of view, one applicable to most non-metal rock styles. It may have taken the guitar community decades to give this amp its due, but hey—better late than never!

Thanks to Robert Hull of myamptech.com and Kirkwood Rough of Upstairs Amps for spotting my build mistakes and protecting me from fire and electrocution.

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