The project, called the 503HTA, packs a single 12AU7 or 6922 tube and a solid-state IRL510 Mosfet circuit into a hybrid amplifier that mounts to 40-pin Raspberry Pi boards, including the Pi 2 and Pi 3. It includes a 24-bit DAC, a gain select switch, and a 3.5mm headphone jack. Putting out just 500mw, it’s designed to power headphones from 32–300 ohms, or act as a preamp for powered stereo and speaker systems. Just be careful when doing that to keep the gain switch at the lowest level to not burn out your amp.
he design is derived from the popular Bravo V2 architecture with all the modifications recommended such as: IRL510 Output Mosfet; Regulated Heater Voltage to reduce cross-talk; Adjustable Plate Bias for Tube Rollers; Nichicon MUSE Output Capacitors; and Jumper-able output impedance of 1.5, 32 and 100 ohm and switchable gain selection to match your headphones exactly.
Technical Specifications
- Raspberry Pi ® HAT Compliant Size w/40-Pin mating connector
- 24-Bit DAC – The well regarded -112db THD PCM5102 is used to convert the I2S Stream to drive the Single Triode Tube Stage at 24-Bit up to 192Khz Frame Rate
- Tube Rolling – The 503HTA supports both 12AU7( ECC82) or 6922/6DJ8 (ECC88) type tubes. Individual Anode Bias Adjustments plus selectable Series/Parallel Heater Drive insure the perfect setup for virtually any tube! See our friends at www.tubedepot.com for some alternate options!
- Headphone Out – Rugged 3.5mm Jack plus selectable output resistance between 1.5, 32 and 100 ohms.
- Gain Select Switch – 3 Gain settings allow the user to select the output voltage to the optimal level for each Headphone. Settings (based on 12AU7) provide approximately 2V, 4V and 6Vrms.
They launched a Kickstarter campaign successfully funded on June 6th, with a 500% result!
Source: Warm Tube Tone Is Just What the Raspberry Pi Has Always Been Missing
