*This is intended more as a one stop shop for general information on the amps and will be slowly added to.
*Amp 2, Amp 4 and Amp 4S are supposedly discontinued.
A useful comparison quick look chart by Mike-Wl on head-fi.org (reproduced with permission).
Also check out Twister6 excellent reviews of a few of the amps:
Average Play Time: 7.5 hours.
The play time varies with different sample rate/bit rates, and headphone/IEM loads.
1. +/-8V voltage swing, equal to 32V voltage swing when compared to single ended. This significantly improves the dynamics and headroom.
2. Patented balanced amplification circuit, that retains all the benefits of a balanced design, such as higher output voltage and lower crosstalk. At the same time, our Patented design has even harmonics that keeps the sound full and musical. *
3. Topology utilizing voltage feedback and current feedback, utilizing the benefits of both types of feedback.
4. OPAMP+BUF architecture, optimized for both high voltage demand and high output current demand monitors.
* With the traditional balanced amplification circuit design, there is a positive signal and a negative signal. They together reduce the harmonics, including both of the odd harmonics and even harmonics. On this amplification design, even though sound is more powerful, the sound is often flat and less musical, as even harmonics are reduced. On the iBasso balanced amplification design, we successfully reduce the odd harmonic, while retaining the even harmonics, thus keeping the sound full and as musical as single ended but with the added benefits of a balanced signal.“-