Valve Preamplifier (2)
In the first part of this article, we described all of the circuit boards. Now it’s time to look at how they fit together. We first describe the mechanical construction, after which we turn our attention to wiring the entire assembly. We conclude with a brief look at the specifications and performance.An important factor with this type of equipment is the enclosure. For the prototype, we selected a standard model from the Conrad line. It consists of black top and bottom covers made from robust 1.5-mm sheet steel and two 1-mm aluminium face panels. The top and bottom covers have ventilation openings. The edges of the face panels are bent at right angles to form lips, to which the top and bottom covers are fastened using four self-tapping screws. The face panels have a brushed matte finish and protective cover foils. For the sake of simplicity, we call the face panel at the front the ‘front panel’ and the other face panel the ‘rear panel’.
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CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.
– Two-section steel enclosure, 300x200x110 mm (wxdxh), Conrad Electronics # 520489*
– IEC appliance socket with internal filter
– Ventilator 40 x 40 mm, 20mm thick, 12VDC
– 2 ABS gearwheels 50.M0.5, Conrad Electronics # 237850*
– S1 = rotary switch, 6 positions, 2 poles, break before make, Conrad Electronics 709751*
– S2 = mains switch
– F2 = fuse 250 mAT (slow), with holder
– LED signal lamp, 12 VDC
– 4 black buttons, 21mm
– 4 button caps, red, with line, 21mm
– 1 button, 28mm
– 1 button cap, red, 28mm