Triode Corporation TRX-1 Line Preamplifier

Tube-Rollers’ Delight

Equipment report
Triode Corporation TRX-1
Triode Corporation TRX-1 Line Preamplifier

Triode Corporation, a successful high-end player in its Japanese home market, has been steadily garnering a positive international reputation. As its name suggests, it specializes in tube electronics with an affinity for triodes. Designer Junichi Yamazaki has been at it for over 15 years, a testimonial to the mass appeal of his designs. No wonder as his design priorities coincide with those of any music lover— affordable gear that stays faithful to the music’s inner beauty. He expresses the company’s essence when he says that “happiness in listening to music is not fulfilled if not shared with many.” The recently released TRX-1 line preamp aptly demonstrates his design acumen.

Attention to detail and execution are superb, as you would expect from a former Japan National Railway engineer. For example, Yamazaki-san spent months voicing various tube rectifiers before settling on the 274B dual-wave rectifier for its maximal dose of midrange magic. My review sample was outfitted with what appears to be a Chinese Shuguang 274B. Running counter to current U.S. design norms, the unit is outfitted with a four-band frequency-equalizer with center frequencies of 150, 400, 2k, and 10kHz, a feature that was popular in the 1970 but has fallen out of favor and unjustly abandoned in the pursuit of design minimalism. The amount of boost or cut is set manually with front-panel pots. Once set, the tone controls can be relay- activated or deactivated via the remote control. When active, the signal is routed through a series of 4558 op-amps, which provide an adjustment range of about +/-6dB. The tone control center frequencies are similar to the classic McIntosh five-band scheme, but with the sensible omission of a deep bass control, which is often abused anyway with subsequent woofer distortion. Some audiophiles seem to possess a Pavlovian aversion to tone controls, but, in fact, such controls offer tremendous flexibility and can be extremely useful in fine-turning a system’s tonal balance for a given acoustic environment. In my room, I found the 150Hz control to be particularly helpful in tweaking the MartinLogan Summit X’s balance. And at least at this frequency I did not observe any objectionable effects in soundstage transparency or harmonic purity when the tone controls were active.

A pair of 12AX7 dual triodes is dedicated to each channel.

The first 12AX7 forms a conventional cascade voltage amplifier, while the second is connected in parallel and configured as a boot-strapped cathode follower. While the 12AX7 may not be the ideal candidate for a cathode follower due to its poor current drive capability, operating both sections in parallel certainly helps in this regard and further lowers the output impedance to a very reasonable 600 ohms because the transconductance of the stage is doubled. Still, I suspect that the TRX-1 would be most comfortable driving a high-input-impedance amplifier. Stock preamp tubes are said to be current production JJ Electronic or Russian Electro Harmonix 12AX7s. The power supply is surprisingly sophisticated for a unit at this price point. Not only are the filament voltages regulated but so is the B+. Resistors are Kiwame brand and signal-coupling caps are Mundorfs. There’s even a full-function remote control, which controls everything except for channel balance. There’s a pot for that on the front panel and it can only be adjusted manually. Volume control, however, is via a motorized pot, which I found a bit touchy to adjust in fine steps.

Right out of the box the TRX-1 impressed with its smooth and warm delivery. Its tube pedigree was easy to discern, no doubt enhanced by the presence of a tube rectifier. Soundstage dimensions and image palpability were exactly what you would expect from a tube preamp. The treble sounded a bit coarse initially but smoothed out over an extended break-in period. However, it became clear over the next couple of weeks that its tonal center of gravity was shifted from a neutral perspective toward the upper midrange. Harmonic textures were slightly bright sounding, a sin of commission I’m not at all tolerant of. Since I’m not enamored of any current production Russian or Chinese 12AX7, the only viable tube-rolling alternative was vintage new old stock (NOS). Although I appreciate the fact that manufacturers cannot rely on the availability of NOS types, especially in any significant quantities, and must source tube types currently in production, I can tell you that the TRX-1 sinks or swims sonically depending on choice of 12AX7. The winner in my tests turned out to be the Sylvania 5751, a lower- gain version of the 12AX7. With 5751s in place, the sound of the TRX-1 took a huge turn for the better. Harmonic textures now possessed a much more natural disposition, sweeter sounding and accompanied by a lovely bloom, though even now, the lower midrange still lacked the weight and oomph of the real thing.

This is not the most resolving line preamp out there. Neither low-level detail resolution nor spatial resolution are in the same class as more expensive preamps. Soundstage dimensions are fleshed out believably but image outlines are broad-brush, resulting in some loss of image specificity. The end result is a presentation that’s the antithesis of analytical sound. So far I’ve painted a picture that would lead you to believe that the TRX-1 may not be an audiophile’s best friend, but here comes the big reveal: I’ve actually developed quite a liking for this preamp. So now for the rest of the story.

The TRX-1 boogies along with plenty of dynamic conviction and is extremely good with timing information, generating an infectious enthusiasm for the music. It may not excel in audiophile terms, but is a standout in its faithfulness to musical values. In particular, it captures the interplay between musicians to an extent that is rare or even exceeds that of preamps costing much more. It is therefore able to readily suck the listener into the performance. The caveat is that you’ll have to invest in vintage tubes, preferably 5751s, and rubber damping rings help, too. With these prerequisites out of the way, the TRX-1 comes alive musically, paving the way for a pleasurable listening experience. An impressive accomplishment at this or any other price point considering what is so priceless about it, allowing one to decompress from a pressure cooker of a day in compelling fashion. Consider it a must-audition if your priority is to simply enjoy the music.


Tube complement: (1) 274B, (4) 12AX7
Voltage gain: 16dB
Frequency response: 10Hz– 100KHz
S/N ratio: 96dB
Input impedance: 100k Ohm
Input sensitivity: 250mV
Output impedance: 600 Ohm
Four-band equalizer frequencies: 150Hz, 400Hz, 2KHz, 10KHz +/- 6dB
Input terminals: (5) RCA
Output terminals: (3) RCA
Power consumption: 30W
Dimensions: 13.4" x 7.4" x 12.4"
Weight: 17.2 lbs.
Price: $3000

TWIN AUDIO VIDEO, INC. (U.S. distributor)
(909) 954-2175


MartinLogan Summit X, Analysis Audio Omega, and BassZilla Platinum Edition mk2 loudspeakers; Sony XA5400 SACD player with ModWright Truth Modification, Weiss Engineering Jason transport and Medea DAC; Kuzma Reference turntable; Kuzma Stogi Reference 313 VTA tonearm; Symphonic Line RG-8 Gold MC phono cartridge; Air Tight ATE-2 phono preamp; SoundTradition Live! MC-10 step-up; Lamm Audio M1.2 Reference, Conrad-Johnson LP125M SE, and Joe Curcio modified Paoli 60 monoblock power amplifiers; FMS Nexus-2 interconnects; FMS Nexus speaker cable; Bybee Speaker Bullets; Sound Application power line conditioners