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Pre and Headphone Amplifier project by Mark Johnson

Noir Preamplifier & HPA

Noir is a unique low cost headphone amplifier project from Mark Johnson. It is a minimalist all-discrete circuit design that exploits the well known advantages of class-A operation.

Noir Preamplifier & HPA

Key Information

  • Pre and Headphone Amplifier Project
  • Designed by Mark Johnson
  • Beginner to Intermediate Difficulty
  • Only PCBs Available
  • Comprehensive Build Guide


  • All-discrete, solid state. No ICs, No vacuum tubes
  • Single ended, Class A circuit operating at 150 mA bias current (exceptionally high for a headphone amp)
  • No mains voltage inside the DIY chassis. Power supply is a commercial, safety rated, DC wall wart followed by a 2 stage supply filter on the PCB

Links, Discussions & Files


Noir is a unique low cost headphone amplifier project, comprised of three circuit boards. The entire Noir BOM is purchasable from Mouser in a single click. Two of the PCBs form pre-made front and rear panels so you can easily form an enclosure. Very cool!

Noir exploits the well known advantages of class-A operation and a minimalist all-discrete circuit design. The amplifier consists of only two transistors (each operated in single ended class-A) giving a very short and linear signal path.

There is a 1/4" headphone jack on the front panel, and preamp outputs (RCA jacks) on the rear panel. Gain is +6 dB. The volume control is an audiophile-quality ALPS Blue Velvet potentiometer.

For more information, to see completed builds or to participate in the community discussion, please visit the Noir diyAudio Discussion Thread. A detailed 37 page Noir Build Guide is now also available to walk you through the construction process.

The amplifier PCB is designed for ease of assembly. All components are thru-hole mounted and are spaced apart generously, making it a breeze to stuff and solder the board. Component IDs and component values are printed on the board, as a further aid to construction. It is an excellent choice for first-time builders. PCB size is 182mm x 112mm, gold traces, and premium 2oz copper thickness.

The amplifier PCB can be installed in a wide variety of chassis. It fits especially well in the Galaxy 1U 230x170mm chassis sold here in the store. In fact, the Noir PCB set includes a front panel and a back panel made of black PCB material (epoxy fiberglass) which fits the 1U Galaxy perfectly. These panels are pre-drilled and pre-labeled, so builders don't need to spend any time in the metal working shop, preparing the front panel or back panel. These panel PCBs don't serve any electrical purpose other than providing ground for the switches.

However should you eventually want to do so and have metal front/back panels, you'll have the original easy-to-work aluminum panels from the original chassis at hand. Noir is a project you can grow into.

You can purchase the PCBs by themselves for $29, or a bundle of the PCBs plus a US-stock chassis (which ships from the US, not Italy) for just $69. As mentioned, the chassis does include the original blank black aluminum front/back panels.


As the saying goes "the proof of the pudding is in the tasting". Here's some feedback from people who have built it, several of whom determined it is their favorite HPA of all time. Others remarked that it is an excellent choice for a beginner's DIY HPA project. 

"After two weeks and rotating thru several of my other HPAs I thought the newness would wear off like so many others, but it's still absolutely stunning... the clarity and openness of this Class A amp is just wonderful...  its the best amp I have heard to date and I have heard a lot of them....(i have 10 in house at the moment)...
- Adyula

" T2 is absolutely amazing. I believe it to be the best HPA I've ever heard"
- 6L6
"Dead quiet with no input and cranked to 11... unmolested, and detailed... balanced well, the treble is clear.. bass end is as good as my headphones will produce...  a very nice, easy to build headphone amp that sounds great - perfect for someone starting out with DIY or as an enjoyable side project for the more experienced builder"
- AVTech23

" For a first time builder, I would recommend Mark's T2. Easier to build, less expensive, and more fun to listen to, as long as you don't need a ton of gain."
- AVDesignGuru