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A beginner's guide to headphone amplifiers

By Kenny Yeo - 12 Aug 2019

A beginner's guide to headphone amplifiers

Headphone amplifiers let you extract every ounce of performance from your headphone, which is crucial if you already invested a good pair of headphone. (Image source: Schiit)

Why do I need a headphone amplifier?

A headphone amplifier does exactly what its name say it does: it amplifies analog music signals so that they are loud enough to be heard. Amplifiers are actually found in any device with a headphone jack - like your smartphone or notebook - but they are usually very basic. This means they might not provide proper amplification to your headphone. Like performance cars that need high octane fuel to function at their best, high-end headphones need proper amplification to sound their best. So if you have invested in a high-end headphone, it must be matched with the right headphone amplifier to unleash their full potential. Here are the three main types of headphone amplifiers that you should know.

 

Solid State

Many solid state amplifiers like the Sony TA-ZH1ES feature built-in DACs, making them complete desk solutions for headphone listening. (Image source: Sony)

This is the most common type of amplifier. It refers to any amplifier that uses transistors in its circuitry. The amplifier in your phone and notebook are examples of solid state amplifiers. They are widespread because they can be made inexpensively and yet effectively. There are some really small desktop solutions that can generate enough power to drive just about any headphone you can buy. Obviously, at the other end of the spectrum, there are also high-end ones that are the size of large gaming systems, use exotic topologies, have Class A designs, and generate enough power to even drive small speakers.

Solid State amplifiers are favoured for their clean sound and high power output. This makes them ideal for driving power-hungry planar magnetic headphones. They are also relatively maintenance-free, unlike tube amplifiers whose vacuum tubes need replacement every couple thousands of hours. However, they are also said to sometimes sound cold and clinical in comparison to tube amplifiers.

Fiio E10K

The budget option - Fiio E10K (S$129)

The E10K from Fiio is not only a headphone amplifier, it is also a DAC (digital-to-analog converter). Connect this to your desktop and notebook and instantly improve its sound and output. It's compact size makes it suitable for all kinds of setups.

Wells Audio Headtrip II

The $$$ option - Wells Audio Headtrip II (US$7,000)

The Headtrip II was designed to be the world's best headphone amplifier and also to drive inefficient headphones like the Abyss AB-1266 and Hifiman Susvara. It features a balanced topology that's heavily biased into Class A power and delivers a whopping 25W per channel at 32ohms and 1.8W per channel at 600 ohms.

 

 

Tube

Tube amplifiers, like this Manley Absolute, are favoured for their organic and warm sound, and also for the way they look. (Image source: Manley)

While solid state amplifiers rely on transistors to tube amplifiers use vacuum tubes to amplify the music signal. They are easy to identify, you will usually see tubes sprouting out of the chassis. The tubes get really hot during operation and this helps cool them and also prevents heat from building up inside the amplifier. There are a couple of different types of tube amplifiers but the most common one you will find are output transformer-less (OTL) amplifiers. These amps are arguably the purest of tube amplifiers because they don’t have an output transformer, which can be a source of distortion. The downside to this is that such amplifiers have high output impedances, which means they only pair well with high impedance headphones - typically about 300 ohms and above. Output transformers get around this problem by transforming the high output impedance of the tube amplifier to match the lower impedance of headphones. Unfortunately, really good output transformers with little distortion are pricey and big, which partly explains why some tube amplifiers cost as much as a car.

Tube amplifiers are preferred by some listeners for their so-called ‘tube sound,’ which is generally referred to as a warm, organic, and rich tone. They are also said to sound less compressed and have a more natural timbre. Swapping tubes in the amplifier can also gently alter the sound, which some enthusiasts find fun and addictive. The downside to tube amplifiers is that the tubes need time to warm up so that they can sound their best and the tubes themselves wear out over time and, depending on the tube, needs to be replaced every couple thousands of hours.

Feliks Audio Echo

The budget option - Feliks Audio Echo (S$769)

The Feliks Audio is an OTL tube amplifier. This means it plays better with high impedance headphones like the Sennheiser HD600 and HD650. It's well-built, retro-looking, and sounds good. Read our review of the Echo tube amplifier here.

Woo Audio WA22

The $$$ option - Woo Audio WA22 (S$3,999)

The Woo Audio WA22 is an all-tube, transformer-coupled amplifier with point-to-point wiring and a balanced topology. It's mighty powerful too, delivering up to 1.5W at 32 ohms and 1.1W at 300 ohms. As a bonus, it looks stunning too.

 

Hybrid

The legendary but now discontinued Cavalli Audio Liquid Crimson is a hybrid tube amplifier that uses a single 6922 tube. (Image source: Headphone Guru)

Hybrid amplifiers are amplifiers that have components of tube and solid state amplifiers. The philosophy behind hybrid amplifiers is to create an amplifier that combines the strengths of tube and solid state amplifiers, i.e., the warmth and organic sound of tube amplifiers and the power offered by solid state amplifiers. Typically, hybrid amplifiers have a tube gain stage and a solid state output stage. Like pure tube amplifiers, you can swap the tubes in hybrid amplifiers to subtly alter its audio characteristics.

Hybrid amplifiers are attractive to music lovers who crave the tube sound but also need an amplifier with high power output. Planar magnetic headphones are a good example as they typically have relatively low impedances and they sound their best when fed with lots of power. So if you want to pair them with a tube amplifier, it should be with a transformer-coupled one. But like I mentioned earlier, a good transformer-coupled tube amplifier can easily cost thousands. This makes hybrid amplifier attractive propositions since they are often less expensive than good transformer-coupled tube amplifiers and can deliver a tube-like sound with high power output.

Schiit Vali 2

The budget option - Schiit Vali 2 (S$349)

The Schiit Vali 2 is one of the most affordable tube hybrid amplifiers you can find. It comes with a single swappable NOS 6BZ7 tube and delivers a serious punch that belies its size — up to 1W per channel at 32 ohms.

Schiit Mjolnir 2

The $$$ option - Schiit Mjolnir 2 (S$1,199)

The Schiit Mjolnir 2 is the big brother of the Vali 2. It features a balanced topology and greater power output of up to 8W per channel at 32 ohms. It uses dual 6BZ7 tubes and can be swapped for any 6DJ8, 6922, ECC88, and 2492 tubes.

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