1. Grounded Grid Plus Tube Preamplifier DIY Kit (Stereo)
2. Variable High Voltage BJT Regulator (2 Set)
3. Assembly Manual
Introduction This Grounded Grid Plus preamplifier provides enhanced performance out of the original Grounded Grid design. This new design adapted a feature like using beta-elminiated BJT current sources to act as constant current sources to bias the differential pairs of the channels separately, whereas only resistors are found in the original design for the current source, which are noise suspectible and voltage dependent. The power rectifier and regulator circuitry is redesigned to support full-wave rectification which is provided as another kit. A lowpass filter with an inductor option is incorporated after the full-wave rectified voltage. There are two independent output voltages (B+: 200-400V DC/100mA) and one independent filament ouput voltage (0-30V DC/3A); they can be fine trimmed by the variable resistors.
1. Three vacuum tube 12AU7 for amplification.
2. Use of WIMA MPK10 capacitors, Nichicon Audio capacitors, BHC Averox capacitors, and Dale resistors.
3. Dedicated power and ground rails for tube power and tube filaments.
4. Symmetry in layout design for both channels.
5. Power requirement: one 200V DC (100mA), one -200V DC (100mA) and one 12.6V DC (1A).
6. PCB dimension: 98mm x 155mm, thickness 2.5mm and 2oz copper, two layers.
Also, it can be easily to reconfigure it to the original Grounded Grid preamplifier. Fore more detail, please refer to the assembly manual.