This pair of F-4 Clone Boards use the same circuit as the Nelson Pass / Firstwatt F-4 model.
The F4 is a Push-Pull, Class-A, Mosfet power amplifier. It is unique in that all of the active devices (transistors) are connected in a 'source-follower' configuration, which makes the amp add very little sonic coloration to the signal, less coloration than most other arrangements.
It sounds very, very good, and is extremely versatile, as each channel can be used separately, or a stereo amp can be run balanced for high power. This is a current source amplifier - it can run any normal speaker, but the F4 needs a preamp that has voltage gain - a passive preamp or buffer will not drive an F4. This amp has no voltage gain so works best when paired with an active preamp that has reasonable gain. Most preamp circuits from the 50's - 80's will have enough, and there are a number of DIY designs made specifically for the F4 as well. It can also be used on the output of a "flea-powered" tube power amp, keeping the tone of the tubes, but adding power enough to run normal speakers. The sonic signature of the F4 is as close to completely transparent as can be built - the tone of whatever you use to drive the F4 will pass though without any alteration.
Please read the Firstwatt F4 manual for more explanation on configurations and use, availiable at www.firstwatt.com
Populate these boards with your own components, then add your own power supply, chassis and heat sinks to complete the amplifier. These generously sized, high quality boards spread the six output MOSFETS for efficient cooling. The mounting hole spacing is the same as all other diyAudio Version 2 UMS boards.
- Running as a stereo amplifier from a single-ended source, 25WPC into 8ohms
- A stereo amp, running as a Monoblock from single-ended source, 50W into 8ohms
- A stereo amp, running as a Monoblock from balanced source, 100W into 8ohms
Power supply requirements
A Bipolar power supply of (+/- 24V) is required. This will require an 18V+18V (or 36V Center Tapped) transformer from 300-500VA, and PSU capacitance of 60,000uF per rail or more. The PSU for the F4, F5, and Aleph J are all essentially identical. See the F5 build guide for details. (F4 guide coming soon!)
The 4U Deluxe Amplifier Chassis makes a great home for this amplifier, and has pre-tapped holes that match the circuit board and transistor mounting positions. The diyAudio "Universal Mounting Spec" (UMS) is a common mounting pattern between the amplifier PCB and the heatsinks. If you utilize the UMS on your heatsinks or use one of the pre-drilled chassis from diyAudio, you will be able to quickly and easily mount different amplifier boards in the same chassis. For example, a 4U 'Jack of all Chassis' with a 400VA, 18V+18V transformer and PSU board, will give you a power supply and chassis where you could try the F4, F5, F5C, Aleph J, and other Pass/Firstwatt amps in the future merely by swapping the amp PCB. The investment in Chassis and PSU needs only be made once.
An Illustrated build guide showing all sorts of useful information on how to build your F4 can be found here: F4 Build Guide.
Please see the F4 thread in the store support forum for any questions you might have and a definitive list of relevant links and resources.
|Dimensions||250mm x 50mm|
|Mounting holes||UMS Heatsink Compatible|
|Number of boards included||2|
I've built a bunch of stuffs starting more than 40 years ago. An with these pass projects things just keep getting better and better. And easier and easier. I don't want to miss lead you, I build tube stuff too, and really love them. They are awesome beautiful art works, elegant and unique. Instruments of music, not reproduction. They make music. Sand amps though, - they are different, and you gotta accept this, but then guys like Allen Wright and Nelson Pass come along, and they've change everything, - for the better, more artful. And this is the accomplishment of our time, to bring back art to this increasingly artifical man-made world. And the more of it we make the not so always better. Man, the times I was born into, guys in the bowery were throwing shit on canvas and calling it art. Well we changed that, now its a wonder to see and hear also again. I've seen art, real art become Ordinary, and I've looked on as we become more artful, and creative without animus, with pathos or love or our collective identity in mind. It makes me wonder if Barack Obama is really John the Baptist. IF so the man is on the way, let the trumpets roars, the Man is on his way. Anyway when I am listen to these amps, the F4's I can think of these thing and ideas together. I can wonder and dream, and can also think the thoughts that can recreate the dream on earth. Both ways are valid and in the right frame of mind together they are a bit of heaven on earth.
fast and as expected.
The quality of PCB is excellent
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