The Neurochrome HP-1 headphone amplifier was an incredible amp – and still is for the fifty lucky buyers of the circuit boards or fully assembled amplifiers. I designed the HP-1 with only performance in mind. Unfortunately, this also meant that the production cost was very high, which made mass-production cost-prohibitive. Thus, I was unable to meet the demand for fully assembled amplifiers once the word of the HP-1 got around. As result, the HP-1 has been discontinued. The HP-1 is superseded by the Tom Christiansen Audio HPA-1, which is available here: » TCA HPA-1 Product Page.
Those who prefer to build their own headphone amplifier, should consider the Neurochrome HP-2. The HP-2 offers 660 mW (50 Ω) at -130 dBc (0.00003%) THD.
The market need for a high-performance headphone amplifier was clear, however. However, customer and reviewer feedback also indicated that the amplifier needs to look and feel good as well. In addition, I found several ways that I could optimize the HP-1 for mass-production without sacrificing performance.
This development led to the Tom Christiansen Audio HPA-1. This amplifier was designed to be mass-producible at a price point lower than that of the Neurochrome HP-1. I managed to accomplish this while only giving up a little bit of output power (the TCA HPA-1 provides a bit over 1 W into 32 Ω versus the 3 W of the Neurochrome HP-1).
The TCA HPA-1 is available at: » www.tomchr.com
Note that the Tom Christiansen Audio products are designed from the ground up as retail products. They will not be available as DIY products.
Similarly, the Neurochrome products are designed as DIY products and will not be available as retail products.