Changed the cap last night and it didn't help any. So i thought about what i had done to change things, as this amp was working before going in its new case. THe only thing that was changed was the inputs/outputs and PSU umbilical chord. I am goign to strip it down and rewire. I hooked up the pre to the other output and all is fine from a DC standpoint. Will check AC soon.
Figured out myproblem, or more precisely, my problems. I had both a ground loop issue and an oscillatio issue. The ground loop was being caused by a speaker terminal making making contact on the interior of the hole. After finding and fixing this, i still had a drop in bias on output stage, but it did not stay steady but varied, showing that the amp was indeed oscillating. I changed the 150R gate stoppers to a generous 332R. Apparently the laterals needed more than the verticals. I need to read up on why. Before i said i could not tell a difference between the verts and lats, but iwas wrong. I now feel like the laterals offer a little quieter background and a little more body than the verticals. They give up a little in soundstage depth, but i find this is more room dependant than most parameters. Oh yeah, Merry Xmas, not Happy Holidays. 
Special thanks to mighty ZM for help.
Special thanks to mighty ZM for help.
I have done a lot of listening and it has led to some questions. I like the IRF outputs for the better soundstage and bass i get from them, but they can't beat the Renasas when it comes to dynamics, imaging, detail, and most importantly, tone. The thing that puzzles me is the cause of the difference. I can see how the IRF fets would have better low end because of the higher gM and greater dampening. Current is the same through both sets, so this seems to be the seperation factor. What i cannot understand is why the Renasas, with all their strengths, seem to pull away fro the listening position and move behind the speakers. Is this a result of lower distortion? Is it the difference in harmonic distribution? It seems the lower the distortion and noise in a system, the more focused the sound is and the less presence and in your face feel you get. ANy comments appreciated. I plan to try both FAirchild parts as well as the fets from the EUVL F5x buy and see how they sound. Right now, I think I a going to stick with the laterals. Maybe i can get some of the bloom or presence back with Salas' 6v6 linestage.
Side note:
If testing a fet for its sweet spot, is it safe to assume that the results you obtain as an individual fet in a circuit will be repeatable in a multi device output? Testing equipment is next purchase.
Side note:
If testing a fet for its sweet spot, is it safe to assume that the results you obtain as an individual fet in a circuit will be repeatable in a multi device output? Testing equipment is next purchase.
Yes and I like them more than the FQA!
But maybe because the speakers are Lowther and my room is very small, so a bit "distance" is good for me....
And the crippled F4 is still more charming...
If you could more specify your question I would send an email to Mr. Pass, so you can be sure he answers (always to me), maybe longer or shorter....
But maybe because the speakers are Lowther and my room is very small, so a bit "distance" is good for me....
And the crippled F4 is still more charming...
If you could more specify your question I would send an email to Mr. Pass, so you can be sure he answers (always to me), maybe longer or shorter....
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