As opposed to discrete designs, the IA502 uses an IC to drive the power stages. The entire power amplifier circuitry for 2-channels are squeezed into a tiny TDA7250 10-pin IC. All that's required are four power darlingtons and some passive components to complete a high performance stereo amplifier. No biasing is required as the IC auto biases the output transistors. The IA502 lends itself well to multi-channel amplification. A 6~8 channel power amplifier can easily be constructed even by beginners.

The TDA7250cfp This 2-channel hybrid IC is normally configured with TIP142/147 power darlingtons for its' output. For those who prefer to use power transistors instead, the TDA7250 can easily be converted. All that is required are a few transistors, 4 additional resistors and some rewiring. This conversion centers mainly on changing the output section to a Sziklai. Sziklai Output In our IA502 on the right, drivers Q1,Q2 are 2SC2238 and 2SA968, and outputs Q5,Q6 are 2SA1216 and 2SC2922 respectively. No instability problems were encountered from this conversion. After a period of run-in, the amplifier remained thermally stable. Is this version worth the extra cost and effort? If one is only interested in something basic, the TIP version would be sufficient. But if one is after sonic performance, I would recommend this version.