Package include
1. DIY Kit based on Marantz 7C Tube Preamplifier (Stereo)
2. Toroidal Power Transformer T30L
3. Assembled Dale 23 Step Ladder Type Attenuator 100K for Volume Control (Stereo)
4. Assembly Manual

 

Introduction
Circuit design is with reference to the classical Marantz 7C. It produces sweet and detail sound. Capacitors in audio grade are used for high voltage filtering and AC signal coupling. Low voltage dropout regulator LT1085 is employed in regulating power supply for tubes filament, which gives a maximum output driving current of the IC is 3A which is far enough for filament power supply. To enhance the performance of the power supply unit, the lengths of power routing path and signal paths are minimized so as to minimize the total path impedances. The placement of the components of the built-in rectifying and regulating circuits are packaged closely together and are far from the amplifier core. Also the R14 and R30 are provided for an alternate the biasing at second amplifying stage.

 

Features
1. Circuit design reference to Walt Jung of American Audio Amateur Magazine.
2. Three Shuguang 12AX7B.
3. Use of WIMA MPK10 capacitors, Nichicon Audio capacitors, BHC Averox capacitors, and Dale resistors.
4. Dedicated power and ground rails for tube power and tube filaments.
5. Symmetry in layout design for both channels.
6. Power requirement: 110-115V AC/220-240V AC 50/60Hz
7. PCB dimension: 110mmx200mm, thickness 2.5mm and 2oz copper, two layers.