This Tube Preamp Has A Nixie Volume Display

The pursuit of audiophile hi-fi is one upon which many superlatives and perhaps a little too much money are lavished. But it’s also a field in which the self-builder can produce their own equipment that is as good or often better than that which can be bought, so it provides plenty of interesting projects along the way. [Justin Scott]’s tube preamplifier is a great example, with its novel use of a pair of Nixie tubes to indicate the volume to which it has been set.

The audio side of the preamp comes courtesy of a four-tube kit from tubes 4 hi-fi, in which we notice another tube as power supply rectifier. The case is a beautifully made wooden affair with a professional front panel, but it’s the Nixies which make it a bit special. A high quality motorised potentiometer is used as a volume control, one of its multiple outputs is used as a simple potential divider to provide a voltage. This is read by an Arduino, which in turn drives the Nixies via a BCD-to-decimal decoder. The attention to detail in the whole project is at a very high level, and though he’s not shred any of its audio measurements with us, we’d expect it to sound as good as it looks.

If tube amplifiers interest you, we’ve delved into their design in the past, and it’s worth directing you to Justin’s matching amplifier, as well.

15 thoughts on “This Tube Preamp Has A Nixie Volume Display

  1. Absolutely awesome! Pulled the same nixies out of old cash register displays in the late 70s and had planned to use them in a headphone amp … as a volume indicator. Knowing little about electronics at that time let alone microcontrollers, I envisioned a stack of PCB disks driven by the attenuator shaft to switch the cathodes LOL!

  2. Why do the tubes stick out the top? Nice solid case like that, and the tubes are on the outside. Idgi. I like tubes, just don’t understand imperilling them like that, just to bonk everyone over the head with “hey look, tubes”

    1. It’s just for the “hey look, tubes” factor. Definitely not about heat dissipation, naw. Back when most amps had tubes, they put ’em inside the case 100% of the time and it worked great. If anything, it’s just making them more vulnerable to microphonics. And smashing, as you say. Maybe a cat licking a top-cap anode every now and then and getting a shock.

      1. I’ve known cats that would use them for zeroing in their new bombsight by using them as the aiming point for the china ornaments they’re shoving off the shelf above.

      2. Qwert—Have you ever seen a tube power amp? Especially a vintage one? Tubes were on the outside especially for heat dissipation. Let’s look at three of the best tube amps ever made—McIntosh Mc275, Quad II, Marantz 8b, and the most common tube amp ever the Dynaco ST-70. All have external tubes–generally with a removable cage to protect kids and cats from burning themselves.

    2. Hi, I am the creator of this amp. qwert has it right: I just think tubes look cool. In my experience people who grew up with tubes are generally mystified by amp designers putting them on display. I grew up with tubes only existing in boutique guitar amplifiers and audiophile equipment. I think there’s more cool vibes associated with them for me than for someone who remembers when every electronic device had them, they were constantly burning out and being replaced, and you could buy/test them at the local hardware store.

  3. Sorry, but yuck. A microprocessor is the last thing in the world I would want in a tube preamp. And nixie tubes? This to me not only falls under the concept of gratuitous electronics but most likely detrimental gratuitous electronics.

    A lot of people like bells and whistles over substance, but it turns me off.

  4. Like the old ‘go fast’ paint stripes down the bonnet (hood) of a car, looks good but doesn’t make the car go any faster
    Same with the nixies, looks good but doesn’t improve the audio quality.

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