The Headamp

An integrated Amplifier sounds bad, doesnt it?
No ! Not if you use a high speed, high current buffer, the BUF634.
This device is a buffer amp (gain=0,99) with a BW of above 100MHz and a SR of 2000V/µs.
Also it delivers 350mA (peak) into ANY Load, starting with 600 Ohm lines downto short circuit!

This buffer is in a feedback loop with OPA 27 and moderate gain of  2.

Supply rails are bypassed by 4x100µF and 1x1000µF each.
The supply for the OpAmps are bypass and filtered by 100µH coils and 100nF (SMD, not seen on Photo, but don't forgot them !)

Output Power (RMS) LOAD
 45mW 1 Ohm  (0.25A2*1Ohm)/ sqrt(2)
180mW 4 Ohm  (0.25A2*4Ohm)/ sqrt(2)
360mW 8 Ohm  (0.25A2*8Ohm)/ sqrt(2)
1,4 W 32 Ohm  (0.25A2*32Ohm)/ sqrt(2)
2,2 W 50 Ohm  (0.25A2*50Ohm)/ sqrt(2)

Maximum output voltage is +/- 12V (if not limited by current)