The Push-Pull circuit for the final loudspeaker amplifier stage as proposed by Sven @ Rigert Forum provides several important advantages. He particularly confirms the following ones:
- Significantly lower power consumption,
- Higher volume (at a given power consumption level),
- Less distortion.
Since these are very important characteristics, I built the circuit myself as well and could confirm these properties. Thus, I decided to design a small 3x3 circuit board to contain the whole circuit so that it could replace the standard BC238 transistor audio end-stage, including feedback resistor and coupling capacitor. As a consequence, some extra advantages emerge:
- Less Philips EE board space required as compared to the original audio end stage,
- Allows any speaker with an impedance of 8 Ohm of higher to be used, so the audio transformer in the later versions of EE2000 and in the EE3000 series is not required anymore,
- It can be used directly in both EE1000/2000 and EE2001 series.
which makes this a highly recommended application. Here below follows all design data needed to make your own board from standard stripboard material:
A picture of the design (an slightly earlier version lacking the decoupling input capacitor):
The corresponding electrical circuit:
The upper and lower (copper trace) sides of the board:
The below two photo's show how the bare stripboad looks like when the four holes are made (with a Dremel tool or similar) and how (with small pieces of blank wire and solder) the four contact pads around the holes can be created:
And finally a link to the sticker file which includes the top design as well (click on the picture for the information link to the design file, the design is on the third ppt-sheet):