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Pair this kit with a Raspberry Pi for the DIY headphone amp of your dreams

Hybrid Tube Amp for Raspberry Pi
For a long time, standalone DACs (digital to analog converters) and headphone amps were something only audiophiles bothered with. Now, with the resurgence in popularity of headphones, they’re getting more popular — but they still aren’t cheap. A new project on Kickstarter, however, has both audio enthusiasts on a budget and hardware nerds excited.

The 503HTA Hybrid Tube Amp by Pi 2 Design looks similar to other kit-based tube amps, but this one has a trick up its sleeve: it uses a Raspberry Pi — supplied by the user — for its brain. The kit itself is HAT — hardware-on-top — compliant in size, and is compatible with any 40pin Raspberry Pi models.

The board uses a 24-bit PCM1502A DAC to drive a 12AU7 tube gain stage capable of driving headphones from 32 to 300 ohms. Output is switchable between approximately 2V, 4V, and 6V — though this will vary based on the tube used — to tailor the amp to specific headphones. The 503HTA also includes Output Relay protection to prevent audible “thump” sounds when the power is turned on.

Early-bird pricing had the kit available for $99, but that has already sold out, as did both $110 tiers. At the time of this writing, a $120 tier is available, but is limited to 100 backers and is quickly running out. When that happens, backers will have to spring for the $150 tier. Both of these tiers offer the amp itself, power supply, acrylic case and mounting hardware, and a choice between a JJ 6DJ8 (ECC88) or JJ 12AU7 (ECC82) tube. Additional tiers are also available, offering a pair of kits.

The initial funding goal for the 503HTA Hybrid Tube Amp was $20,000, and only a few days into the campaign, it has already raised more than 250 percent of that original amount, nearing $55,000 at the time of this writing. Pi 2 Design has introduced one stretch goal, unlocked at $75,000, which will add a pair of adapter cables with each kit shipped: one 3.5mm to 1/4-inch to allow high-end headphones to be plugged in, and one 3.5mm to stereo RCA to allow the amp to be plugged into other stereo gear.

The campaign will come to an end on Monday, June 6, leaving potential backers plenty of time to pledge. For more information, see the campaign page on Kickstarter.

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