Quote:
Originally Posted by Jaybird
After playing my amp a while today, I decided that I like it better stock, so I reverted all the mods. I was never able to get that NFB resistor to function properly, The 25uf cap "leglift" just made the amp sound spotty and gargley, so now everything is stock except I left in the .1 coupling caps, I am really likeing the amp again. I sort of ABed it with my new 5F1 and they both are pretty sweet. I must say that I believe the 5F1 is a little richer sounding though. This is a great thread with some good ideas and timely responses.
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Originally Posted by specialty guitars
"Yours is a unique one for sure. I can't imagine lifting that 25uF cap would make it sound "spotty and gargley", when all it does is reduce gain. NFB can be a tricky issue. I do wonder if the .1uF caps made it unstable. Yours is the only one that's had those problems (that we know of), and it's the only one with different value coupling caps. Amp circuits are kind of a "balancing act"."
Strange stuff. While switching from an 8 ohm speaker in the 8 ohm input, to a 4 ohm speaker into the RCA input, my amp developed a case of very low power and volume. I must have spent the better part of 2 days checking out what might be wrong. As it turned out, the 4 ohm tap on my OT appears to not work, while when I use the 8 ohm tap, the amp is as loud and clear as ever. Is that possible?
In the process, I discovered (after removing the board from the chassis) that the wire from pin #3 to the cathode resistor, was hooked up to the bypass cap, not the resistor. That is why when I tried the mod of lifting the bypass cap leg, my amp sounded like it was in a can. After looking at various pics from this thread, I confirmed my suspicion that the wire should be connected differently. I drilled a hole in the board , ran the wire through and connected it to its proper home on the cathode resistor. So while wired this way (by a human at the factory) the amp worked, after a modification as in this thread, the amp would not function. My guess is that it was misswired. Easy enough to wire to the wrong spot from the underside. On my amp the underwires are soldered to the turrets from below, not run through holes and wired from above, where mistakes are easier to spot. Possibly why they started drilling holes in the chassis for this purpose.
I am not sure if I am going to do the mods at this point. I have another project to do, and need to take a break from this amp and just play it a bit.