Rane MA6 Multichannel Amplifier

In 1988, Rane released the MA6, a quality 6-channel power amplifier. There are six discrete power modules packed into a 3U chassis, each capable of 100W into 8Ω, 150W into 4Ω and 300W into 8Ω when in Mono-Bridge. Best of all, the transistors used are very high grade, like the Sanken MT-200 2SC3858 and 2SA1494. These power transistors are normally seen in High-End amplifiers. For a commercial amplifier like the MA6 to sport them indicates the designer is sound conscious.

Fig 1 – Rane MA6 Amplifier

Fig 1 is the circuit of the MA6. At first glance, she looks very similar to the Peavey CS800 of 1976. The outputs are in Full-complementary instead of the CS800 Quasi. Apart from that, the typology is the same.

The front end is an op-amp which drives a transistor at her output (Red line). This transistor has a 1kΩ resistor at her collector. This can be construed as one-half of an input differential. The amplified signal is fed to the next stage, the VAS. In this stage, two 2.4kΩ resistors at the top determine the standing current. Together with a 470uF capacitor, they form what is known as a bootstrap constant current source. The VAS output is fed to a Driver which in turn powers the output transistor.

Fig 2 – Rane MA6 Amplifier Modules

Fig 2 shows the six power modules inside the chassis. There is one large heatsink at the bottom that all the power transistors from the six channels are mounted to. In the module at the right, the Sanken MT-200 2SC3858 and 2SA1494 are clearly visible. For cooling, there’s a fan that’s located at the rear of the chassis

Summary

Even though the Rane MA6 started out as a multichannel amplifier for the commercial market, she is ideally suited for Home Theater use. 100W into 8Ω is plenty power for domestic applications. The only weakness I can see is there’s only two pieces of 10,000uF/80V filter capacitors in the PSU serving all six channels. Ideally, I would prefer 20,000uF per channel. That would mean a total of 120,000uF.

That’s impractical for a commercial product as cost being a major factor. Furthermore, buyers will not appreciate the value of more capacitors. Nonetheless, it doesn’t distract from the fact that the MA6 is a very well made amplifier and is good value for money.