In my post entitled “Jaguar Reference Systems – circa 2010” I talk a lot about my modified F5 clone amplifier, which uses the circuit of the First Watt F5 (refer back to that post for more description of the sound). I’ve made a lot of modifications to amplifier. My First Watt F3 had been soldered by the hands of Nelson Pass himself, so making mods to that amp would have been a crime. However, tinkering with a clone is no big deal and right now I can’t think of much else to do to this amp.
Note: The link below shows an illustrated guide to building an F5 yourself. This is a relatively simple project. You will find several other posts on the site about the project, including information about where to buy circuit boards.
http://www.diyaudio.com/forums/pass-labs/188691-illustrated-guide-building-f5.html
After I bought this amp I traded the wimpy stock transformer for an oversized Plitron transformer, replaced the diodes (next to the transformer) with Schottky fast-switching diodes, replaced the cheap electrolytic caps with exorbitantly expensive Jensen 4-pole caps, stripped out the wiring and replaced with Acrolink 7-nines pure copper wire, replaced the IEC with an upgraded Furutech part, replaced the wiring to the RCA input jacks with silver-plated copper in Teflon and traded the stock fuse for a Synergy HiFi fuse in the fuse holder. To top it all off, the entire circuit was cryo treated (see the post about Cryo, for a cautionary tale). I also have an Audio Magic Pulse Gen ZX module installed between the caps and transformer (not pictured).
In total I spent an additional $1,500 modding this unit. I have no idea how it compares to a standard clone or a real First Watt F5. None of the mods seemed to make a major difference by themselves, but I’m fairly happy with the overall sound. My friend, who is very experienced with electronics helped me with the tougher jobs, like installing the caps and the Acrolink wire. I made a big mistake by using 10 gauge Acrolink wire (instead of 12 or 14 gauge), because it was way to large for the holes in the circuit boards and had to be modified to fit. We spent about 10hrs on the upgrades and I could never have done the job without his skills and equipment, but I learned quite a bit.