What is a Valvecaster?

But how does a Valvecaster work?



This is an awful sketch of the first Valvecaster, composing the "green" channel or the booster for the "red" channel.

It is built around the 12AT7 tube system, composed of two triodes packaged together, each of which amplified its input signal. The circuit is very easy to follow, at least in its basic functioning. The input signal is fed into the first stage, dubbed 12AT7(a), via a decoupling input filter (to prevent DC components and low-frequency hum). This stage amplifies the signal with a gain controlled by the variable resistor VR1. Subsequently, this amplified signal is injected into the 12AT7(b) stage, held at the maximum gain. A decoupling filter is in order since we just want the alternating signal (music) and not the DC bias applied to the anode. The output from this stage is again decoupled. A simple voltage control is provided with a partitioning VR2 resistor.

There it is! Neat and effective!