hardware internet tech

A 3.3 V Tube Preamp Without An Inverter

If you’ve ever labored with vacuum tubes, you’ll most probably have a wholesome appreciation for prime voltage energy provides. These elements require upper potentials to get the ones electrons transferring, or so we’re informed. It’s now not the entire fact even though, as [Albert van Dalen] demonstrates along with his tube preamplifier operating from best 3.3 V. If your first concept is that he should have made a flyback converter to step that voltage as much as one thing extra helpful then you definately’re in for a wonder, since the unmarried 6J6 pentode truly does run from simply 3.3 volts. Even its heater, typically provided with 6.3 V, takes the decrease voltage.

The circuit seems to start with sight to be a standard single-ended design, however nearer exam finds a grid bias circuit extra paying homage to a bipolar transistor. This leads to a favorable grid voltage moderately than the extra same old adverse, and an surprisingly top 0.3 mA grid present. The cathode present is best  0.15 mA, however the preamplifier delivers a 3.5x achieve. There is extra element on his site.

It can be attention-grabbing to topic this circuit to a complete audio research and comparability with a extra typical design. As with such a lot on this planet of audio there’s some smoke and mirrors round what constitutes the so-called “valve sound”, and it’s a query whether or not the delight comes in the course of the sound itself or the bragging rights of getting a unit with a vacuum tube on display.  Still, this can be a easy sufficient design which takes few assets to construct, so we look ahead to seeing additional experimentation. Careful even though – down the vacuum audio path can lie folly.