Now With More Gain!
Updated schematic added, see the last page...
Plus, it's low-voltage--no more than 13V, so it's perfectly safe for "tube neophytes" to build. No high-voltage dangers with this one. It can even be powered with a 9V battery (but read the step on "Powering Options.")
With only a few inexpensive parts and a simple circuit, this should be an easy first-time tube project!
I didn't use a video cam mic, so the "youtube" audio is halfway-decent quality. But the mp3 file (look below, beneath the pictures) is much better...it's same audio track.
Step 1: Background
Matsumin's project uses 12AU7 tubes, and is a very worthy build. This build, the ValveLiTzer, uses a slightly more oddball tube: the 12FQ8. Why use a weird tube? Because I have about 25 of 'em, and no guitar amps or stompboxes use them. So why not build something?
But the 12FQ8 isn't a typical audio tube. It's a twin-triode, but with 4 plates, and a single shared cathode. Would it even work as an audio amplifier? Only one way to find out...
Why the name ValveLiTzer? These tubes came from the tone generator in a defunct WurliTzer organ.
There are a few web comments (re: are 12FQ8's appropriate for guitar amp use?) but no one to my knowledge actually has to date. Certainly more complex applications are possible.
See they next page for info on procuring the tube (unless you find an old WurliTzer...)