Building Compact F5 Amplifier (Part 4 Final) It's Sound Great

This F5 project is continued once my order of 2SJ74 from Spancer arrived last week. As you can read from part 1, part 2, and part 3 this F5 amp is almost finish. I have tested one channel and working very well. This amp works without hum, noise, or any pop noise. I can say it is a dead quiet amp.

Some member in my local online forum providing me the information related the very rare J74 and ZTX transistor. One of them providing me the ZTX transistor and the other suggesting me to go to fetaudio.com to buy the J74.

And this is the package from Spencer. It takes a month for shipping.

And this how I done for both channel. It is very compact and neat.

I am aware about the size of the heat sink is smaller than the recommendation, that is why I only setup the bias for less than 500 mV per channel. It is bellow as the recommendation. During testing, the heat rises quickly but still tolerable. I could hold my hand on the heat sink for more than 6 second. Now lets see the DC offset at the output. The value is under 10 mV and mostly at zero DC offset. It is perfect!

And this is how it sound: wonderful! The depth and resolution of the music is open wide. The micro detail of each instruments are pronounce very clear. I have listening to my Gainclone for years and I could tell this F5 is a jump to enter the true hi-fi amp. I love how Gainclone sound but this F5 is much better in many ways.

I've read people claim about weak bass from this F5 amp, which I could tell that they are very wrong. The bass level are correct and frequency response can go even lower with this F5 amp. One thing I highlighting this amp is the heat. It is a common for every class A amp. I play this amp for an hour and the heat could cooked an egg. I am using additional fan to directly blow this amp. This fan help a lot to cooling down this amp during operation and now the temperature at moderate level which my hand could barely touch it for so long.

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