Unison Research TRIODE 25 Push-Pull Integrated Valve Amplifier with USB DAC at Vinyl Sound Buffalo, NY USA

The TRIODE 25 is a push-pull EL34 integrated valve amplifier with built-in USB DAC from Unison Research (Treviso, Italy), available at Vinyl Sound in Buffalo, NY, USA. Created to celebrate Unison Research's 25th anniversary and developed as the successor to the long-running Triode 20, the TRIODE 25 was awarded a 5-star review by What Hi-Fi? magazine and praised for its sonic delicacy, dynamic fluidity, and terrific build. Switchable between triode and pentode output modes, the TRIODE 25 delivers approximately 45 watts per channel in pentode mode and approximately 25 watts per channel in triode mode, with a 32-bit/384 kHz and DSD 128-compatible USB input for high-resolution computer audio playback. The tube complement of four EL34, two ECC83, and one ECC82 is operated in a push-pull ultralinear Class-AB output stage fed by a symmetrical output transformer for linear signal reconstruction.

Push-Pull Architecture and Switchable Output Modes

The TRIODE 25 employs a push-pull output stage -- a topology in which two pairs of EL34 output tubes amplify opposite halves of the audio waveform before recombining them through a symmetrical output transformer. This architecture offers higher output power than single-ended designs, improved efficiency, and the elimination of DC polarization in the output transformer -- all factors that contribute to lower distortion and greater bass control at higher output levels. Unison Research has engineered the individual amplification stages of the TRIODE 25 with particular attention to the suppression of odd-order harmonic distortion, which is the primary sonic liability of push-pull designs when the two half-stages are not perfectly matched. A selectable feedback level of 5 dB or 1.8 dB further allows the user to adjust the amplifier's damping factor and tonal character to suit different loudspeaker loads. What Hi-Fi? described the TRIODE 25 as delivering sonic delicacy and insight with impressive refinement and dynamic fluidity.

32-Bit USB DAC and Computer Audio Integration

The TRIODE 25's built-in USB input operates to the USB 2.0 Audio Class standard and accepts PCM data up to 32 bits and 384 kHz, as well as DSD64 and DSD128 in native or DoP (DSD over PCM) format. This specification supports every studio-mastered and high-resolution download format available from services such as HDtracks, Qobuz, and NativeDSD, making the TRIODE 25 a fully integrated solution for computer audio without the need for a separate DAC. Pentode mode, with its 45-watt output per channel, provides additional headroom for demanding loudspeaker loads or larger listening rooms. Triode mode at approximately 25 watts per channel engages all four EL34 tubes in a lower-power, purer triode configuration associated with greater harmonic richness and midrange transparency. An RC2 remote control with black wood finish is included as standard.

Key Features

• What Hi-Fi? 5-Star Review: The TRIODE 25 received a 5-star review from What Hi-Fi? magazine, recognized for sonic delicacy and insight, impressive refinement and dynamic fluidity, and terrific build quality.
• Switchable Triode and Pentode Modes: The output stage can be switched between triode (~25 W/ch) and pentode ultralinear (~45 W/ch) at any time, including during playback, for immediate comparison of both output characters.
• 32-Bit/384 kHz USB DAC with DSD 128 Support: The built-in USB input accepts all current PCM and DSD high-resolution formats for computer audio playback without an external DAC.
• Push-Pull EL34 Output Stage: Four EL34 tubes in a push-pull ultralinear Class-AB configuration with a symmetrical output transformer provide higher output power and improved bass performance relative to single-ended designs.
• Selectable Negative Feedback: 5 dB or 1.8 dB feedback levels allow adjustment of damping factor and sonic character to suit different loudspeaker loads.
• 25th Anniversary Heritage: The TRIODE 25 was released as part of Unison Research's 25th anniversary in 2012, honoring and succeeding the original Triode 20 design.
• RC2 Remote Control Included: Black wood-finish IR remote governs volume and input selection from the listening position.

Technical Specifications

Awards and Critical Recognition

• What Hi-Fi? -- 5-Star Review: "Yet another superb design from Unison Research. Great to use and even better to listen to."

Frequently Asked Questions

What is the Unison Research TRIODE 25?

The Unison Research TRIODE 25 is a push-pull EL34 integrated valve amplifier with a built-in 32-bit/DSD 128 USB DAC, manufactured in Treviso, Italy. It produces approximately 45 watts per channel in pentode mode and 25 watts per channel in triode mode, with switchable feedback levels of 5 dB or 1.8 dB. It received a 5-star review from What Hi-Fi? magazine and was released as part of Unison Research's 25th anniversary celebration.

How does the TRIODE 25 compare to the Unison Research Simply Italy?

The TRIODE 25 and Simply Italy are both EL34-based integrated amplifiers from Unison Research, but they differ substantially in topology and power. The Simply Italy uses two EL34 tubes in a single-ended Class A output stage producing 12 watts per channel, with a 6-ohm output impedance and self-biasing design. The TRIODE 25 uses four EL34 tubes in a push-pull ultralinear Class-AB configuration producing up to 45 watts per channel, adds a built-in 32-bit USB DAC, and offers switchable triode and pentode modes. The Simply Italy is the purer, lower-powered single-ended design; the TRIODE 25 offers significantly more output power, digital connectivity, and mode versatility.

What is the difference between triode and pentode mode in the TRIODE 25?

In pentode mode, the EL34 output tubes operate as pentodes with their screen grids connected to a fixed supply voltage, producing the full rated output of approximately 45 watts per channel with greater efficiency and higher damping factor. In triode mode, the screen grids are connected to the plate, causing each EL34 to behave acoustically as a triode: lower output power (~25 W/ch), a softer clipping character, and a harmonic structure weighted toward lower-order even harmonics associated with a warmer, more romantic midrange. The TRIODE 25 can be switched between modes during playback.

Can the TRIODE 25 play DSD files from a computer?

Yes. The TRIODE 25's USB DAC supports DSD64 and DSD128 formats in addition to PCM up to 32 bits and 384 kHz. Compatible playback software includes Roon, Audirvana, and HQPlayer, all of which can output DSD natively or via DoP over the USB connection. The USB input uses the USB 2.0 Audio Class standard, which is compatible with Windows, macOS, and Linux operating systems.

Where can I buy the Unison Research TRIODE 25 in Buffalo, NY or the USA?

The Unison Research TRIODE 25 is available at Vinyl Sound in Buffalo, NY, USA. Vinyl Sound is an authorized Unison Research dealer serving western New York and the United States. Contact Vinyl Sound for current availability and in-store demonstration arrangements.