A re-working of a familiar theme suitable for 25-0-25V transformers...

which again withstands updating (PDF) for 30-0-30V transformers (below).

A compact (PCB = 120 x 76mm) fast high-end design that is worth looking at although, for its' size, considered too complex for some.

Of the three designs presented here personal preference would opt for the first.

Be mindful that supersonic power bandwidths can be wasteful, damaging and unnecessary giving rise to distortion when the output and load are dissipating energy unrelated to the music being played. Quite often an upper limit of 30kHz can be sufficient.

A pre-amplifier design (low-noise, wide-band, no eq/filtering) by Giesberts ('Battery-operated pre-amplifier', elektor, 1/97 p14 and 2/97 p36) offers interesting solutions. Match this with the 'AF input module' (elektor, 7-8/97 p80) and 'AF input selection' (p103) although mechanical switch contacts can disappoint.

For a high-power (1kW+) Giesberts design, see the Titan 2000 (elektor, Feb '99, p60).