Juergen Grau located in Rohrbach, Germany has
designed and created a new STC Super Triode connection power amplifier Mk II
Bausatz which has this week launched by a Kickstarter to raise the required
funds it needs to make the jump into protection. With pledges available from
€ 329 or £ 288 the project is hoping to raise just € 4,500 over the next 30 days.
The special feedback circuitry results in: 1st: The
triode now “sees” the limited frequency response and distortions due to the
modulated Anode voltage of the Pentode. The feedback circuitry adds these
errors to the audio signal. Due to the 180° phase shift of the inverting power
amplifier stage (negative feedback) these distortions will be eliminated and
the frequency response is flattened.
In a way, the Triode “supervises” the
Pentode power amplifier stage. 2nd: Normally the feedback path is connected to
the Triodes Grid but in this case it’s connected to the Anode so the Triode
“sees” only the Pentode’s distortions (and eliminates it) but not its own
harmonic distortions.”
