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

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.

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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.

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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.