Find out how to adjust the bias.
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There is a guy named John "something" I believe which is in california, or was a couple years back that was a threshold designer, and he would convert all these amps to pure class A for a small fee.. He would replace some power supply stuff like rectifiers, and up the beef on the caps etc and do it with newer parts and reliability.
He did all the fortes as well and highly recommended going class A if you can.. I owned a sweet little forte that was mint and got stupid selling it due to moving out of a place and not having a system for a while, but well worth it.. Look up "Threshold Repair services" on google or something and you should be able to find him and his small mod company if its still around, I am sorry I just don't remember all the details.
He can do a bunch of mods to these things, and a big one if I remember correcly is actually removing those out of date monster caps by replacing them with custom boards that actually takes many smaller caps that are faster, higher end, and more reliable, basically taking banks of good new caps and upping the capacity of the values as well as adding several more for higher current, faster, sweeter, more reliable sound.
Of course who knows today, doinga all this at a price you might just by some new Class A mono's and be done with it! At least contacting him he could maybe give you the basic rundown if its possible to do yourself with the existing design.
Yes, Jon Soderberg is unquestionably the guru with Thresholds & Forte. I have corresponded with him, and I'm considering sending the amp to him. $530.00, though, not including shipping from east coast to west coast & back. I'm a pretty handy guy, and I'm wondering if I can make the conversion myself. Any advice out there?? Thanks.
"Any advice out there?? "
I think you answered your own question, he would be able to tell you! I doubt he witholds much info just because you don't send it to him, he would know all the pitfalls you can encounter, and if this can be a simple enough conversion with the existing parts and no upgrades. Beyond that I am sure he will tell you "Yeah you can do this, this, and this and get it to the basic Class A operation" if in fact this is possible without changing anything.. Other than that I am also sure he could sell you the correct parts if you plan to push the entire upgrade yourself. Nobody else here can give you better advice on this subject for sure so call him up, hell even a 50 dollar consultation fee would be better getting it directly from him. He probably has or can write up a simple conversion technique or compatable schematics, tell you the milli amps to bias each channel too etc
That's a pretty good idea. I haven't asked Jon if he could give me instructions, because I know he does this for a living. Offering him a consultation fee would make me feel better and hopefully make it worth his time. I know I would get more satisfaction if I could do it myself. I'll drop him a line. No harm in "fishing around" for others' experience, though. Anyone out there made this conversion before? Thanks.
When you say you are handy, does that include working around high voltages, soldering, using a VOM. etc. I don't think this is a simple as swapping out a couple of parts. I could be wrong. also be sure your physical set up can handle the high heat load. FWIW, the 50 watt Forte Class A amps were honeys, but I think you can probably buy one for $500> Of course your "newly modded" one would presumably have all new caps which at the age of the Fortes are likely to require replacement on any used one you would buy.