Granddad, there’s a tube on my Raspberry Pi

May 10, 2016 | 15:50
Granddad, there’s a tube on my Raspberry Pi
Granddad, there’s a tube on my Raspberry Pi
“Yes dear that’s a 12AU7 or ECC82 there, nothing special to me”.

I knew it had to happen some day: the Raspberry Pi goes back in time by the addition of a vacuum tube.  Pi2Media (a division of Pi2Design) have pulled it off, but with a twist. They say their 503HTA Hybrid Tube Amp HAT is the first tube amp specifically designed for any of the 40-pin versions of the Raspberry Pi SBC family, giving it that “Sweet Tube Sound”. This HAT allows the RPi to drive headphones from 32 – 300 ohms with ease and fidelity.

The caveat here is the word Hybrid, meaning an IRL510 FET in Class A and assisted by an LM317 (yuk) is actually powering the headphones, and the little tube acts as the driver only.

For Granddad and dad only:  the 503HTA also has an on-board 5 V / 3 A regulator allowing the HAT and the Pi to be powered from a single, 24-V external supply.  You get a 112 dB THD PCM5102 for I2S stream conversion to drive the single-triode stage at 24 bits up to 192-kHz frame rate; the 503HTA supports 12AU7 (ECC82) or 6922/6DJ8 (ECC88) tubes; there’s individual anode bias adjustments plus selectable series/parallel heater config's.;  also, 3 gain settings to match headphone with the 12AU7 settings yielding 2 V, 4 V and 6 Vrms out.

For the whole family: you can read more info on the project on KickStarter. Expect Granddad to pay around $99 including the 24-V 2-A supply.
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