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HA75 Tube Head™ Headphone Amplifier

  • 100% discrete class-A audio circuit with 12AX7 tube drive
  • Variable Focus™ control to simulate listening in a room
  • Adjustable negative feedback to tailor signal path
  • Choice of unbalanced RCA or balanced XLR inputs

The Hafler HA75 is a ‘vintage inspired’ headphone amplifier that has been meticulously designed to produce Hafler’s legendary sound quality while adding excitement and character of a real tube circuit to optimize the listening experience.

The design begins with a 14 gauge steel casing to shield the internal workings from external magnetic fields and RF contamination. This is complimented with a black anodized aluminum front panel for clean, esthetic appeal. A choice of either unbalanced RCA or balanced XLR inputs are available. These are gold-plated to eliminate tarnishing over time while optimizing signal flow.

Inside, a 100% discrete class-A head-amp combines with a 12AX7 tube drive to power the headphones. This employs a unique non-radiating charge pump that applies 140 volts to the tube to maximize headroom as it delivers the character and warmth that so many listeners prefer over solid state counterparts. Unique to the HA75 is a negative feedback control. This enables the user to increase or decrease the negative feedback to produce either a more ‘clinical’ (solid state) or a ‘warmer’ (tube) response, further enhancing the signal path for the type of program material that is at play. To simulate the response of listening to loudspeakers in an acoustic space, a Focus control may be engaged that brings the stereo image to the center via a fully variable potentiometer. This active control activates a matrix that delivers exciting results without collapsing the stereo image. A Vox function warms the tone akin to an old-school loudness control, addressing the Fletcher-Munson curves to deliver equal loudness when listening at low levels. The Vox control can also can be used and create a ‘boom-box’ effect for those that enjoy a more exaggerated response.

The HA75’s heavy duty amplifier stage is able to handle all types of headphone impedances from 8 Ohms to 400 Ohms without choking as it quietly delivers plenty of warmth and character to truly enhance the listening experience.

Dial In

  1. Power
    Activates the device and the 12AX7
  2. Feedback Control
    Increase the 'warmth' by adjusting the tube response
  3. Level
    Used to set the headphone output level
  4. Focus Control
    Brings the left and right channels to the center to simulate listening to music with speakers in an open room
  5. Phones
    ¼" TRS output for headphones. Works with headphones ranging from 8 Ohms to 400 Ohms

Connect

  1. Input A
    Selectable RCA or balanced XLR connectors.
  2. Input B
    Unbalanced RCA phono jacks
  3. Thru-put
    Whichever input is selected appears at the thru-put in an unbalanced format
  4. Tube Out
    Add the Tubehead's warm tube character to a signal path between a preamp and power amp
  5. Power
    External power supply included

Inside

  1. Tube Drive
    Dual triode 12AX7 tube operates in stereo with a B+ voltage that reaches 140 volts to deliver the warm sonic advantages of a tube without excessive distortion.
  2. 100% Discrete Audio Circuit Path
    Instead of today’s popular surface mount ‘cell phone’ parts, the HA75 uses full sized resistors and capacitors that are hand inserted to deliver the very best audio quality.
  3. Extra Durable Switches
    Ultra high quality switches and potentiometers employ steel casings and metal shafts for long-term reliability.
  4. Glass-Filled XLRs
    Glass impregnated nylon XLR connectors are tougher than steel, feature extra-large nickel-silver pin contacts for positive connection that will not tarnish over the years.

Specs

Audio Circuit:Discrete class-A with 12AX7
Inputs:Switchable RCA or XLR
Thru-puts:RCA (left/right)
Output:1/4" TRS Headphone
Impedance:8 Ohm ~ 400 Ohm
Gain:30 dB
Max Output:5 V RMS

FAQ

Can the HA75 damage my hearing?

Yes. Any time you are subjected to long periods of high sound pressure levels, you can damage your hearing. Always monitor your kids' listening levels and consult local health and government safety regulations to ensure you stay within safe margins.

What is the benefit of tubes?

Tubes introduce warm-sounding even order harmonic distortion that is pleasing to the ears. This is why most audiophiles prefer the sound of tubes over solid state counterparts. The other benefit is the distortion acts like a natural limiter. This tends to reduce ear fatigue.

Do I need to warm the HA75 up before using it?

Yes. It takes about 15 minutes to achieve thermal stability. This of course produces a better sound as all of the components reach their optimum temperature.

Can you explain negative feedback?

Negative feedback is used to control the amplifier from thermal runaway. This also results in less noise. However, may purists prefer to have as little negative feedback as possible in the signal chain to reduce phase cancellation. With the HA75, you can adjust to suit your personal taste.

Why did you incorporate a bass loudness switch?

Some will argue that true audiophiles may never use this function. However, when listening to music at low levels, bass energy can become too low. The loudness switch allows the user to add more bass to suit. This also allows users that enjoy listening to accentuated bass to share in the fun.

Why an external power supply?

External power supplies enable manufacturers to ship the same product around the globe without having to pay costly safety certificates. This makes the product more affordable for the end user. Further, power supplies tend to be the part of the circuit that is most subject to fail. This makes servicing easy. Finally, power supplies generate a ton of noise. This is particularly troublesome in small boxes. So removing the power supply lowers the noise floor.

Reviews

The Master Switch

It's all about control. At TMS, we’ve got no truck with jargon-heavy explanations - the only things we’re interested in are good sound, and making it easy to understand audio gear so you can get good sound. But sometimes, in order to achieve that good sound, you need to play around with a piece of equipment that demands you fiddle a little bit, and become a little bit obsessive. Step forward, then, the Hafler HA75 – an amp which came out in 2015, but which is still widely available at an excellent price. And as we’re about to show you, you might have to be a bit of a nerd to get the most out of it, but it is so, so worth it...

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Tape Op Magazine

These days, pro audio's end products often live in the "Headphones World." The home stereos of the past have been supplanted by the mobile devices of today. Fewer listeners have full-size speaker systems, and much listening is done through various grades of "personal monitoring," be it earbuds or headphones of varying quality levels. The key takeaway for an audio professional: A final master needs to sound good in the Headphones World. To accomplish this goal, excellent headphone monitoring in the studio is key.

Tom Fine

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I've complained in blogs about, well, almost everything, but lately one focus of my ire has been headphone amps. Everyone's coming out with one, and they're almost all the same: a headphone amp and a DAC chip stuffed into an extruded aluminum box. Whoop de doo. That's partly why I was so shocked when I was paging though a copy of JazzTimes and saw an ad for the Tube Head HA75 headphone amp: The HA75 actually has features I've never seen before - features that seemed like they might be useful... What's so special about the Tube Head HA75? Almost everything.

Brent Butterworth

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The folks at Hafler are helping break down the long-held convention that mixing with headphones is bad with the HA15 and HA75 Tube Head headphone amplifiers. The focus knob and the warmth of these units had me checking my mixes more critically than ever before. It's great to have Radial, a Canadian company, furthering the legacy of such a high quality-product.

Adam Gallant

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