Allnic ASRA RHPA-7500 Tube Headphone & Speaker Amplifier

There are tube amps, and there are tube amps. It is often said that the biggest determinant of a tube amp's quality is the output transformers used. A poor quality output transformer ruins the beautiful signals from tubes, muddies and smears midrange from the bass, and suffers from poor high-frequency extension. Enter Allnic: the masters of permalloy transformers. 

Why permalloy over standard silicon-steel transformers? Permalloy is greatly permeable, which means it magnetises even at very low signal levels, excelling at transferring faint signals without losing information. Allnic's permalloy transformer-coupled amps have great linearity from 20hz-20000hz (+-0dB), more so than standard silicon-steel transformers. Lower coercivity of the permalloy transformers also mean the magnetic domain walls move easily, reducing distortion, and minimising transformer-associated losses in signal purity. Permalloy is an expensive material, so it is not commonly used even in high-end audio applications. 

Allnic's ultimate goal with permalloy transformers is making the transformer feel like it disappears, pushing the amplifier to sound akin to an OTL/OCL. This is what transparency would really mean. The RHPA-7500 has exceptional openness and scale similar to the best OTL/OCLs. 

Allnic's RHPA-7500 is a push-pull tube amplifier with dual permalloy output transformers. It is really a headphone amplifier that has speaker-level power for drive stability. Triode (10W) and pentode (20W) mode switchable. Triode puts the tube's noble, pure and refined nature in the forefront, whereas pentode pushes the tubes into a more energetic, large and authoritative presentation. 

But how does it actually sound? The RHPA-7500 on Triode Mode is a lightly warm, smooth yet exciting tube amplifier to listen to. It oozes liquid smooth mids, and has pristinely detailed highs without any semblance of harshness. Bass is tight, yet never rock solid rigid like a solid state's artificial bass. It's akin to a smooth, warm wave gently gushing around the soundstage, putting you at ease. Make no mistake however, it is not a typical tube amp that lacks detail. The RHPA-7500 is immensely detailed, yet never boastful. Its soundstage is really wide, dare we say even surpassing amplifiers of any kind even above its price range. We recommend to do most of your IEM and headphone listening on Triode Mode.

And Pentode Mode? Pentode brings the amp to a maximum of 20W output, and shifts the tonal balance to be more exciting and energetic. It opens up soundstage even further and excels at conveying high frequency detail without grain. It still largely retains the liquid smooth sound, and bass becomes tighter and more rigid. We recommend Pentode for truly power hungry headphones like the Susvara, or to be used in conjunction with speakers. 

Allnic has also used the lesser known 7558 pentode beam tubes, which feature a lower amplification factor and lower transconductance than the EL84, which make them excellent for use in a headphone amplifier. 

This amplifier also comes with options for standard potentiometer or Allnic's Constant Impedance Attenuator (CIA). The CIA preserves dynamics and tone regardless of what volume level you are at. It is probably the world's best volume control. As far as we know, only Allnic does this. 

Tubes provided: NOS ECF80 × 2 / NOS 12AU7 (6211) × 2 / NOS 7558 × 4
Output impedance range: 10ohms to 300ohms
Outputs: 6.35mm jack, 4-pin XLR jack, dedicated drive 4-pin XLR for Ribbon headphones
Dimensions (W,D,H): 35.5cm (14 inches) x 44.5cm (17.5 inches) x 14.0cm (5.5 inches)
Weight: 16.3kg