Alchemist Forseti APD15A RC Integrated amplifier

We recently had a customer present this faulty Alchemist Forseti integrated amp for repair – I’d guess this dates from the 1990’s and has been well looked after. It’s a bit of a bruiser as you can see from the extensive heatsinking!Alchemist Forseti APD15A RC Integrated amplifier

Unfortunately it developed a DC fault on the loudspeaker outputs and destroyed the customers speakers, so it’s now in the naughty corner awaiting surgery.

Access to the internal circuitry is via the top panel, which is secured by 13 cap head screws.

There are 13 screws to remove in total, an allen key is needed.

The rear panel has good connectivity for analogue sources (all line level, no phono input  but there are two pre-outputs to drive extra power amps should you need even more power.

Once the top panel is removed, this is the view of the printed circuit boards and power supplies – it’s very nicely laid out.

The Forseti is constructed as a dual mono design, which should give better channel separation and therefore improved stereo image – here is one channel’s output stage which employs two pairs of output transistors per channel – 2SA1302 are the PNP transistors and 2SC3281 are the NPN making a class B push pull output stage.

Each amplifier channel is fed power from it’s own dedicated power supply comprising 200VA toroidal mains transformer, bridge rectifier and four 10000uF/ 50V resevoir capacitors.Alchemist Forseti APD15A RC Integrated amplifier schematich

All of the the inputs are electronically switched by relay to keep signal paths extremely short for best possible sound quality.

The Forseti is a very well constructed amplifier which promises excellent performance – we will have to wait to hear this until we have diagosed and fixed any issues.



For more detail: Alchemist Forseti APD15A RC Integrated amplifier

About The Author

Ibrar Ayyub

I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough research and presenting information in a structured and logical format.

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