Inspiration

USB Type C can deliver more electrical power than the older USB standards. It should be enough to run a vacuum tube amplifier.

What it does

You plug it into a USB port and you plug your headphones into it. You play your music. It combines the vintage warmth of tube audio with the modern convenience of USB Type C.

How I built it

I soldered electrical components together starting from a USB C breakout board. The vacuum tube circuit runs off 12v, so a buck-boost module was used to increase the USB supply voltage of 5v to 12v. A cheap digital-to-analog converter was also attached to the breakout, supplying an analog signal to the tube circuit.

The actual tube circuit was based on this. It uses a low voltage 12AU7 dual triode vacuum tube and two IRF610 MOSFETS operating as a Class A amplifier.

Challenges I ran into

Initially, the tube amp had the interesting property of picking up AM radio signals. Faint music would be played even when no signal was sent through USB. This was solved by placing a resistor between the tube's plate and the input capacitor.

Accomplishments that I'm proud of

It works.

What I learned

I gained a lot of experience working with analog circuits. I learned wiring techniques such as avoiding ground loops to obtain a good quality audio output.

I also learned that my earbuds were reversed in polarity. The one labeled for the left ear actually receives the right ear's signal. This solved a lot of mysterious "issues" of a polarity reversal somewhere in my circuit.

What's next for USB C Tube Amp

Building a case for it.

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