This Vacuum Tube Preamplifier Features a Nixie Tube Display and Motorized Volume Knob

Justin Scott's PH-16 vacuum tube preamp includes a two-digit Nixie tube volume display and a motorized volume knob with remote control.

Cameron Coward
4 years agoMusic / Retro Tech

If you really care about the sound quality of your music, you aren’t going to be happy with the tinny sound of a cheap Bluetooth speaker or TV sound bar. Audiophiles can easily spend thousands of dollars on their home stereo systems. But, even among those enthusiasts, there is a lot of debate about which equipment is best. Do you want absolutely clean audio that reproduces the recording with perfect accuracy, or a system that adds a bit of warmth? Justin Scott was going for the latter, and constructed a vacuum tube preamplifier with a built-in Nixie tube display and motorized volume knob.

As far as the general public is concerned, vacuum tubes are obsolete technological components. But for guitarists and audiophiles looking for a particular kind of sound, vacuum tube amplifiers are ideal. Technically, the “warm” sound of a vacuum tube amp is the result of minor distortion from the tubes, but it is pleasant enough to be desirable. Scott's build started with a high-end PH-16 phone preamplifier kit from tubes4hifi.com. A complete PH-16 kit costs more than $700 after shipping, but the quality is quite good. Even so, the PH-16 is a “no frills” design without any controls other than a power switch. Scott's modifications dramatically improve on that design.

Scott designed the improved PH-16 enclosure in OnShape CAD software and created technical drawings to send to his father-in-law who does carpentry. A few weeks letter, he got back a beautiful cherry wood enclosure. Scott then added to the new components. Those include a two-digit Nixie tube volume display, a motorized volume knob with remote control, five selectable inputs, two selectable outputs, and a tone control to reduce bass when necessary. The motorized volume control was a prebuilt unit sourced from the eBay, and the Nixie tubes are controlled by an Arduino Nano board. The result is a fantastic vacuum tube preamplifier that looks better and is more convenient to use than the standard PH-16. It’s just one piece of Scott's stereo system, but it is an important one.

Cameron Coward
Writer for Hackster News. Proud husband and dog dad. Maker and serial hobbyist. Check out my YouTube channel: Serial Hobbyism
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