Based on the Mitsumin Valvecaster circuit, this simple design is a 12AU7 preamp running on a mere 9V DC. I’ve found this thing to be useful for guitar, synth, and samplers giving a warm, lively edge to any small signal. It features Volume, Tone, and Gain controls. High gain results in a warm vacuum tube break-up while lower gain provide sonic color and texture.
Here are two audio samples of the triode. The first is made with two synthesizers (a Korg DW-6000 and a Novation Xiosynth) while the second is for guitar (a Johnson Telecopy). The first is recorded direct with no signal processing added except for a 6dB signal boost in the clean signal of the last set. The guitar samples were recorded on a Tascam DR-07 with a Bulgera 333 amp. Each section features a clean section followed by an effected section and so on. Each effected section adds more gain and volume each time through starting in the middle ranges and increasing to higher range. Maximum tone roll-off is demonstrated on the second variation of both demos.