This amplifier design really excels in simplicity and robustness, thanks to the
use of the TDA2030 or TDA2040 “power op amps”, The power supply of the amplifier is built with bridge rectifier and elcap capacitor. Further stabilization is not necessary because of the high supply voltage ripple rejection (50dB).
Here are some features :
The speakers are from the high-end series of Tonsil , good drivers built with conventional technique.The passive filter is second order (12dB/oct) and has a cross-over frequency of about 2.5 kHz.A pcb is not necessary, the filter components can be “hard wired”, all parts can be secured in the case with silicone.source
The Chu Moy Pocket Headphone Amplifier is a very simple, yet, quite good sounding amplifier. As the name says, it is intended for use with headphones. This little amp can be very effective in combination with a discman for example. You could put the discman volume at a very low level, thus using less battery power. The amplifier only needs a minimum number of parts and can be build as small as the 9v battery it needs for power. However, it’s not possible to convert that layout into a PCBsource
The PPA is a high-end headphone amplifier that works for both stationary and “transportable” amplifiers. There is a high-capacity fast-charging NiMH battery supply available, allowing excellent sonics without sacrificing run time despite the PPA amp’s hunger for power. While only the most dedicated audiophile would take it jogging with their iPod, this combination makes for a fine travel amplifier.
This is one of the stronger amps based on LM3886 application note. It supports stand-by and mute modes. The schematic is rather complicated, because there are some additional devices in the feedback and there are filters both on the input and on the output.The application note contains two alternative topologies: the first one is simple, the second one contains output DC error correction using a servo feedback. The funny thing is, there’s not just a single servo per channel – there are four of them, one for each power IC.source