Tuesday, May 5, 2020

Pass F5 turbo extreme build







I was commissioned to build this F5 Turbo for another. The kit is from Diyaudio shop and comprises a 5U extra heavy enclosure with steel subchassis, two 300VA trannies and double PSs. This allows the construction of a dual mono amp. There is a total 192,000uf of filtering audio grade caps and 16 dual high performance diode bridges all on their own heat sinks. Each diode bridge is capable of 15As.

The F5 boards looked first class. The components were all high-end and selected by the owner. Riedon resistors featured strongly and a few other resistors were beefed up to bring the amp to turbo specs. Also large power thermistors are placed on both legs of the mains to allow for a soft start. Matched power FETs and matched high performance driver FETs were also chosen.

To push the amp to turbo the idle current is raised to 1.6A across each power FET. Though the heat sinks are massive they still get to 50c and can only be touch briefly. This high current mode was requested by the owner. Bias is fiddley and a little vague but with persistence you can get the current up and the DC offset down.

The amp is extremely quiet and has no sound at all when on. It is beyond any of the quietest amps I have ever built. It has a dead back background. From this back hole of nothingness leaps extreme dynamics with a sweet and detailed mid and treble. Bass is deep and swings a little to the bloomy side but not unpleasantly so. This is amp is to drive 100db sensitive Zu Druids. I wish I could be there to hear it. In my system is was an expensive but extreme giant killer. May build one myself. 




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