Ashdown Classic Tube Magnifier CTM-300 Amp Review

Back in the day, if you wanted serious volume and tone, you had to schlep some heavy-duty and very heavy amplifiers. This was thanks to those mighty transformers powering all of those wonderful vacuum tubes—all housed on a thick chassis and protected by a solid-wood frame. Just ask any bassist what they used back in the day to compete with those stacks of Marshalls or Hiwatts. Though the comments may be accompanied by a groan or wince, they’ll likely reminisce about the good ol’ days when they moved SVTs up and down multiple flights of stairs.

Today, many bassists swear that tubes are still the ultimate transmitter of tone. Yes, there are plenty of digital pedals and preamps on the market that emulate the sound of tubes at work—and many are getting better at doing so—but no microchip has truly succeeded in replicating the natural compression and dynamic warmth that tubes provide.

Because a large demographic of tube-advocating bassists still exists, there are bass amp builders who continue to try to build a better mousetrap. One such company, Ashdown Engineering, has manufactured amps of nearly every shape and size over the years, and most recently, they’ve gone for the “full monty” with their Valve Series of amplifiers. The most traditional member of this team is the Classic Tube Magnifier—an all-tube, 300-watt beast that boasts some modern enhancements.

What’s Boiling My Electrons?
Peering through the top grille, one can quickly tell that the inspiration for the CTM-300 is rooted in British tube past. Bookended by two transformers, the CTM-300 houses six individually fused KT88 output tubes. This clever design allows the amplifier to function in case one of the power tubes fails. And for the quintet of preamp tubes, the CTM-300 utilizes an ECC83, ECC832, ECC99, and ECC82 (2x) configuration.

The front panel is a unique mix of vintage simplicity and modern technology. The typical high- and low-sensitivity inputs introduce the bass signal to the preamp, offering clean or potentially overdriven options to the signal. Below the inputs is the effects loop, typically found behind an amplifier. But this is arguably an ideal location for the loop, since most players run a pedalboard in front of their rig. Ashdown also gave frontal placement to the DI, along with the pre/post EQ switch located right above it, which might be pleasing to some soundmen. The tone-shaping area is straightforward, with bass, middle, and treble knobs, as well as switches to manipulate the EQ’s frequency ranges. And Ashdown wisely placed the mute switch right above the master dial, which allows a player to quickly alleviate a potential swell of feedback.

The self-biasing system and Ashdown’s characteristic VU meter are two very impressive components to the CTM-300. Historically, tube amp users had to either be savvy with the biasing process or frequently haul their unit to a trained technician. With Ashdown’s tube-selector dial, a player can select one of six positions, with each position corresponding to one of the power tubes. And when the audio/bias switch is pressed, the VU meter displays the performance of the selected power tube. If an adjustment is required, it’s made in the back of the unit where the tube’s trimmer can be tweaked with the turn of a small screwdriver. This may seem awkward, but the process is not only quite simple, it’s cost-effective since it can help minimize those pricey servicing fees. The other benefit of the dual-function VU meter—outside of looking cool and furthering the vintage vibe of the amp—is that it indicates the output level when in audio mode.

The Tube Musketeer
Tell any bassist they are about to move a 300-watt, all-tube amp, and chances are their face will get pretty serious while their upper body starts to swell like Bruce Banner turning into the Hulk. This wasn’t the case with the CTM-300, even though it weighs almost 73 pounds. The unit was relatively easy to move with its top-located handles, which allow the muscles in the hands and arms to effectively support the amp.

Powering up this monster on top of a Glockenklang Quattro 410 cabinet, the CTM-300 produced a clean and warm tone, indicative of the KT88s. It also delivered notes with impressive response, be it Jaco-esque 16th-note runs from a 1964 Jazz bass, or dotted eighth- or 16th-note patterns on a Nash P-style bass. These characteristics carried over into a blues quartet gig, where the CTM-300/Quattro combo sat well within the mix, preserving its sonic space against a loud drummer and a Fender Super Reverb.

Compelled to hear the tubes cook up some overdriven roars, I knew it was time to crank up the gain and master dials. Since the neighbors were home, I took the CTM- 300 over to a friend’s studio where he and two fellow bassists had a bevy of instruments ready to play through this British beast. Utilizing an SVT 8x10 cab, we also organized a quick taste test of sorts by setting up the CTM-300 next to the American tube titan, a “Blue-Line” SVT.

Whether it was a late-’70s Fender P or an ’80s Wal 4-string, pushing the overdriven CTM-300 through the SVT cab conveyed a thick snarl to bass notes, as well as our faces. This distorted tone satisfied a couple of the most discriminating of players, who typically wield modified Big Muff and Bluebeard fuzz pedals. Compared to the SVT, the CTM-300 was a bit shier in the low end, with the SVT producing more warmth and big volume. But the CTM-300 was the clear winner when it came to a cleaner, more natural sound.

The Riddle of the Dials
While there were plenty of positives with the CTM-300, I found its passive EQ section to be somewhat frustrating. Proponents believe that passive EQs are more musical, as they are meant to provide subtle enhancements to an instrument’s overall sound. The CTM-300’s EQ, however, required some extensive experimentation since the knobs and switches reacted quite differently to each bass.

We played a total of ten different basses from a variety of manufacturers through the CTM-300, and while the treble knob consistently delivered various amounts of highs, the bass and middle controls would best be described as temperamental. For example, when a P-style bass was plugged into the CTM-300, the bass and middle controls had little to no impact in enhancing the instrument’s sound. Yet when an active bass (like the late-’70s StingRay in the lineup) was plugged in, the aforementioned knobs did provide low-mid tone-shaping. The switches shifted their respective frequencies, but depending on the instrument, the knobs’ activity ranged from generous to non-effective.

The Verdict
The CTM-300 is another nice addition to the wide spectrum of tube amplifiers that Ashdown has developed. It’s a solid nod to the amps of old and its self-biasing feature and thoughtful layout are welcomed upgrades to a classic formula. Those who prefer an overdriven sound and a simple signal chain might find the CTM-300 a good option, for its overdriven tone could allow you to leave your pedals at home. And while the CTM-300 also delivers a very clean and responsive tone, the amount of tone-shaping flexibility may not be enough for some bassists when considering its hefty price tag.