The CHI was designed as an easily portable amp that Lifeson can reach for when a last-minute show pops up. It’s ostensibly “Marshall-y” in attitude, though it’s also very much a modern-voiced circuit with footswitchable clean and lead channels. It generates 30 watts via two 6L6EH output tubes and three 12AX7s in the preamp and phase-inverter stages. It’s a straight-ahead amp, wonderfully free of excess features to throw you off course. And while it's perfect for the diehard Rush fan (manual-suggested settings for several Lifeson signature tones, including “Limelight,” “Fly by Night,” and “Working Man,” confirm as much), there’s plenty here to satisfy guitarists outside the Canadian prog-rock obsessives club.
Greek to Me
The CHI exudes a businesslike demeanor, but it’s also stylish enough to stand apart from the scores of lookalike classic clones out there, dressed up as it is in race-grey levant vinyl, red-garnet piping, and black-matrix grille cloth. The logo panel sports a striking red font inspired by the text on the iconic Moving Pictures album cover, and the control panel carries an etched Starman graphic that lights up red when you flip the power switch (there’s no standby on this model). The 24" x 20" x 9", 49-pound amp, with its Baltic birch cabinet, feels solid and substantial, too. Mojotone’s reputation for quality cabinets extends back further than its amplifier business, and the company has supplied many top boutique amp builders. It’s easy to imagine why.
“Access to the fluid, singing tones that define much of Lifeson’s playing with Rush is easy.”
Controls include input gain, lead master, output master, treble, middle, bass, and presence, and there’s a pull switch for a “rhythm clip” function on the input gain, which adds a little dirt to erstwhile clean tones. Around back, you’ll find a jack for the single-button footswitch, a send and return for the effects loop, two 8-ohm speaker outs, and a single 16-ohm out. Inside, the CHI’s circuit is wired across a primary printed circuit board. Three smaller boards host output-tube connections, effects send/return and speaker outs, and the LED array that lights up the Starman. Workmanship is tidy throughout, with neat wire runs and tube sockets that are bolted to the chassis for support in addition to their connections to the respective PCBs.
The CHI’s 30-watt rating comes courtesy of cathode-biased 6L6s. The configuration slightly reins the power from these tubes, which can produce around 45 watts in a fixed-bias configuration, but they can often sound a little juicier and more harmonically complex when cathode biased. The setup also means you can replace the output tubes without having to reset their bias. (We will say, though, be careful when removing or reaching behind the amp’s upper-back panel: A sharp edge on the roughly cut protective screen left this reviewer with a slice on my index finger.)
A Ride in the Red Barchetta
Tested with a Gibson ES-355 and a Fender 1956 Stratocaster Reissue, the Lerxst CHI swiftly revealed itself as a versatile performer—able to do far more than the expected Lifeson-alike tricks that would appear to be its raison d’etre. Going straight to the gained-up lead channel with input gain set at 2 o’clock or more—a route that’s hard to resist on an amp like this—accesses a boatload of muscular grind, sustain, and sizzle. Attaining the fluid, singing tones that define much of Lifeson’s playing with Rush is easy. Dial down the input gain to noon or below, though, and you can tap into plenty of earthy, rootsy rock ‘n’ roll tones. A little tweak here and there delivers everything from gritty classic rock to dirty blues to gnarly garage-rock tones.
Rhythm channel tones will stay relatively clean at pretty hot settings, so you can play loud without sounding muddy. This capability will be a boon for texturalists who need headroom for detailed time-based and modulation effects. But the rhythm channel also works great with overdrive pedals (a TS10 Tube Screamer and Wampler Tumnus Deluxe both sounded excellent). Pulling out the input gain knob for rhythm clip is also an effective tool for adding dirt to the rhythm foundation. The overall level drops slightly, too, but since it’s not a footswitchable function you’re more likely to use this very practical mode with its own gain settings.
With that in mind, it’s worth noting that the CHI’s gain staging, and the knobs that control it, take some getting used to. Since input gain controls the drive level for both channels, you’re tied to finding a compromise between them, then balancing the lead output via the lead master control, and the overall volume of both channels at the output master. Including just one more knob to allow for both rhythm gain and lead gain controls would be more intuitive. As it is, the setup certainly works once you get the hang of it, and both channels can sound great, but it sometimes requires a little deviation from your ideal tone on one channel or another.
The Verdict
The Lerxst CHI combo is a convenient, versatile amp with more than enough punching power to keep up with a heavy drummer, and still sounds great when reined in to basement practice levels. While saturated rock sizzle is very much its forte, the medium-grind overdrive tones are appealing, and both cleans and clipped settings on the rhythm channel are useful and satisfying. Independent rhythm and lead gain controls would have been a plus, but the CHI combo has much to offer just as it is, whether you’re a Rush fan or not
Alex Lifeson Lerxst Chi Amp Demo by Zach Wish — Run the range of Rush riffage! | First Look
Fig. 1
More dB Terms?
What is dBFS? It is relegated to the digital realm, and whenever you hear this term, I want you to remember the following joke: “What sounds better than digital distortion? Everything!”
You see, dBFS (decibels full scale), is the unit of measurement for amplitude within a digital system (such as your DAW), and all digital systems have a maximum peak level before clipping (overload) occurs. A reading of 0 dBFS is the highest signal level achievable for a digital audio. Unlike the analog world, where brief moments of being “in the red” of the VU meter won’t adversely affect the audio, dBFS digital “overs” are squared off (or, mercilessly guillotined), and clipping occurs. It sucks, and is to be avoided at all times. The audio irony is that, when or if you see those two teeny-tiny rectangles above your master fader turn red (Fig.1), you’ve got big problems, and need to turn everything down in order to avoid clipping when you bounce/render your mix.
Is a 100-watt amp twice as loud as a 50-watt amp?
I’m going to answer this by helping you learn some more about how we perceive loudness, and I’ll be using dBA as our mode of measurement. Because, as you’ll recall from last month, using dBFS treats all frequencies equally, and that’s not how the human ear works. In other words, our sensitivity to frequency, sound level, and duration vary across our general range of hearing (20 Hz to 20 kHz). Specifically, our hearing has evolved to be most sensitive between the approximate ranges of 2 kHz and 5 kHz.
Using this range as a yardstick, audiologists agree that 3 dB (up or down) is the minimal detectable change the average person can hear. In my experience, in a critical listening environment, I—and anyone else in the studio—can easily hear 1 dB changes—this especially happens when mixing and mastering.
“The audio irony is that, when or if you see those two teeny-tiny rectangles above your master fader turn red, you’ve got big problems.”
However, to increase the sound, 3 dB requires twice the power (intensity). An increase of 6 dB requires twice the amplitude (voltage), and an increase of 10 dB sounds to the human ear twice as loud. Stated another way: +3 dB is 2x the acoustic power, +6 dB is 4x the acoustic power, and +10 dB is 10x the acoustic power. For those who are mathematically inclined (I am not), here is the decibel formula: dB = 10log10 (S1/S2), where S1 and S2 are the intensity of the two sounds.
Remember when I said last month that decibels are based on a ratio, and they are logarithmic? Now we want to look at the relationship of decibels and power. What is the international unit of measurement for power? It’s the watt (W), named after Scottish inventor James Watt (1736–1819). Check out these relationships:
| Number of Decibels | Relative Increase of Power |
| 0 dB | 1x |
| 3 dB | 2x |
| 10 dB | 10x |
| 20 dB | 100x |
| 30 dB | 1,000x |
| 50 dB | 100,000x |
| 100 dB | 10,000,000,000x |
So, let’s say we have a lovely vintage 4x12 cabinet, and we have two amps that we are going to run through it—a 50-watt head and a 100-watt head (both with matching impedance). Using this relationship, we can answer our previous question! Our 50-watt head is the starting point and baseline for measurement.
Let’s say that, as we play our latest epic jam through our dimed 50-watt head, our drummer comes over and says, “It’s not loud enough! They can’t hear it in the parking lot of the Waffle House across from the stadium!” So, we switch to the 100-watt head thinking it will be twice as loud. Wrong! Go back and look at the chart above. We’ve doubled the power (2x) and that only gained us a paltry increase of 3 dB! That’s right, a 100-watt amp is only 3 dB louder than a 50-watt amp. So, what would be twice as loud? Do the math—we’d need a 10x increase in watts (50 W × 10), so a 500-watt amplifier (or 10 dimed 50-watt amps, simultaneously) would be needed! (Yes, but do they go to 11?)
Until next time, namaste.
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