Headphone Amplifiers

ALO Studio Six Tube Headphone Amp Review


ALO Studio Six Tube Headphone Amp Review Highlights

The ALO Studio Six is a Class-A single-ended triode circuit design with zero feedback. It delivers a warm and rich tone via its full vacuum tube amplification. It isn't cheap but it delivers a lot of quality tube power for its cost. I found the Studio Six to pair wonderfully with the Audeze LCD-3 planar magnetic headphones.

Secrets of Home Theater has reviewed some of the latest headphone amps over the last few years. And even though the ALO (AudioLineOut) Studio Six tube headphone amplifier has been out for nearly a year, I could not turn down a chance to review it. The unit is big, heavy, and built to last a lifetime, yet still beautiful to look at. The Studio Six is built with enough power to drive multiple pairs of 32ohm or greater headphones, and it does so with grace and musicality. The ALO Studio Six is not a small investment at $3900, but in return you get a hand built, here in Portland, Oregon in fact, single-ended vacuum tube amp encased in high-grade aluminum. If you are looking for that mesmerizing harmonic signature SET tube designs provide, and want an amp made to last a lifetime, the Studio Six is one of the very best options available. Your wallet may not thank you, but your ears certainly will.

ALO Studio Six Tube Headphone Amp Review

ALO Studio Six Tube Headphone Amp Highlights Summary

  • • Beautifully lush, musical, warm sound
  • • Quiet for tube
  • • Built to last a lifetime
  • • More power than you could ever need
  • • Allows for multiple listeners

Introduction to the ALO Studio Six Tube Headphone Amp Review

As a Portlander myself, I have known about ALO (AudioLineOut) for many years and even used to work a few blocks away from their old store front. ALO focuses mainly on personal/portable audio with a wide range of beautifully made high end cables along with their crowning jewel, the Studio Six. The Six is a fully tube-based headphone amp meant for home and designed to power high impedance headphones.


  • Design: Tube Headphone Amplifier
  • Headphone Impedance Compatibility Range: 8 Ohms to 600 Ohms
  • Amplifier Input Impedance: 95 kOhms
  • Amplifier input Voltage for full-rated Output Voltage into Various Headphone Impedances:
  • 1.00V RMS Input for 4.0V RMS Output into 16 Ohms
  • 1.30V RMS Input for 5.7V RMS Output into 32 Ohms
  • 1.70V RMS Iput for 7.5V RMS Output into 75 Ohms
  • 1.85V RMS Input for 8.3V RMS Output into 150 Ohms
  • 1.70V RMS Input for 8.2V RMS Output into 300 Ohms
  • 1.65V RMS Input for 8.1V RMS Output into 600 Ohms
  • THD+N (1 kHz Input) at 1V RMS Output into Stated Load Impedances: 32 Ohms: 0.26% / 150 Ohms: 0.12%
  • THD+N (1kHz input) at 250 mW Output into Stated Impedances: 32 Ohms: 1.0% / 150 Ohms: 2.0%
  • MFR: -3dB (Referenced to 1kHz, 250 mW Output) into Stated Impedances: 32 Ohms: 6.0 Hz to 39 kHz / 150 Ohms: 16.5 Hz to 36 kHz
  • MFR: -1dB at Full-rated (2.83V RMS) 1,000 mW Output into 8 Ohms: 15 Hz to 20 kHz
  • S/N Ratio: 78 dB (unweighted) below Full 2.83V RMS Output into 8 Ohms
  • MSRP: $3,900 USD
  • ALO Studio
  • SECRETS Tags: ALO, Studio Six, Tube Amp, Headphone Amp, 2014 Headphone Amp Reviews

My first real audiophile setup used a Jolida integrated tube amp and it gave me the opportunity to hear the benefit of using vacuum tubes for music. Of course there were a few drawbacks, like tube replacement and the occasional bias adjustment. Fortunately, with the Studio Six’s over-built engineering, you don’t have to worry about bias adjustments and the circuit is designed for long tube life, although you might find yourself experimenting with other tubes. The Studio Six is big, it’s beefy, and it’s an all American design, built right here in my home town of Portland, Oregon.

Ken Ball, president and founder of ALO Audio, was kind enough to give me a tour of their office on the east side of Portland.

ALO Studio Six Tube Headphone Amp Review

ALO Studio Six Tube Headphone Amp Review

Inside this office they are handling all the design, testing and manufacturing of ALO products. All those beautiful cables they make are braided and terminated right here in Portland, on this incredible looking piece of machinery:

ALO Studio Six Tube Headphone Amp Review

And the early prototype of the Studio Six:

ALO Studio Six Tube Headphone Amp Review

ALO Studio Six Tube Headphone Amp Review

The Studio Six is hand-assembled here with many parts, including the aluminum chassis, locally sourced. A lot of tweaking and testing of different parts went into the design of the Studio Six, along with plenty of blood, sweat and tears from Ken Ball, circuit designer Thomas A Martens, and the ALO Team. All that passion has paid off and if you have made the plunge into the warm bath-like waters of high-end personal audio, then the ALO Studio Six is the ultimate tube amp with which to drive those high performance headphones.

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