DIY Headphone Tube Amp Builds On Existing Design

DIY Tube Headphone Amp

[Simon] wrote in to tell us about a headphone tube amp that he just built. It is based on schematics at that were actually featured on Hackaday in the past. [Simon's] design adds an on board regulated power supply and a volume control for the input. Effort was made to keep the PCB single sided to facilitate making this at home.

DIY Tube Headphone AmpThe 12AU7 is popular due to its ruggedness and tolerance for low operational voltages. This amp design uses a plate voltage of 12, although the 12AU7 can handle up to about 330.  Since the 12AU7 is of the Twin Triode variety, one tube can be used to amplify both a left and right audio channel.

The case for the amplifier is laser cut plywood. The top piece is kerfed so that it can bend around the radii of the front and rear panels. The top also has a hole cut in it to allow the tube to peek out through.The pieces look nice but, unfortunately, he doesn’t show the case and amp in an assembled state.

If you’re interested in building one of these, [Simon] made all of the Eagle and Case files available. The total cost of the project was £25, about $43 US. To learn more about how tube amplifiers work, check out this Retrotechtacular from earlier in the year.

Tube amp monitor

Sparkfun contributor [Pete] really loves tube amps, but he’s a very safety-conscious guy who doesn’t like being electrocuted. This is a problem, since tube amps are usually very high voltage, and a small mistake can be fatal. To deal with this voltage issue, he built a tube amp with a control system built around a 6DOF v3 controller board. The control system is there mainly in case of a failure, automatically shutting off the high voltage transformer in any such event. It has the added benefit of filtering any 60Hz noise from getting into the audio, which happened before he installed the control system.

In addition to regulating power, the controller board also monitors bias points in the output tubes and displays its diagnostics on an LCD. Aside from getting great sound from the tube amp, [Pete] made it look great too, installing colored LEDs under the tubes. We love his design: just because safety comes first it doesn’t mean cool-factor can’t come in a close second.