[TV MAN]

In my 1st build of the same project I used couplers that I got from AES - some white ones, and that amp sounded pretty good. The 2nd one has been difficult from the start. For some reason I only ordered 2 of the white caps to "try", then couldn't get more when I tried to order, so I stuck the yellow caps in that came with the kit - generic China ones. Thought cap was cap. Noope! I had all sorts of weird problems and didn't sound that great either. I ordered those brown ones, thinking they were like Orange drops from AES, but still 'lacked something' in sound quality. I don't have any scope comparisons, but I ordered IC caps from AES for my EL34 builds and tried those and - yes, there was a difference. Much cleaner more transparent sound. So, there is a difference and I can sense it. Worth going out and buying $100 x2 caps? Naaaah! But def something quality like Solen, Sprague or IC. And value matters too, go too big and they sound muddy, too small and they sound tinny and lack bass. Seems .1 to .25 is about right.

It's kinda weird how things work out sometimes, I just threw my 1st amp together doing about what seemed right at the time figuring I'd end up redoing about half or all of it for tweaks and changes. That one worked flawlessly! Aside from a few tube swaps, I haven't done anything to it. The 2nd amp I revised and neated up. Figured I'd redo the 1st the same way. Yes, it looks much neater - but I've had that thing apart and together more times than I care to mention, changing everything from caps to tube sockets! I finally did get it working good, but they still don't sound quite the same. I am going to try some different output trannys and feedback settings.

On the scope reading, I'd found a bad NOS 6GH8a tube that was also causing weirdness, so I switched to a JAN 6U8a and that solved a lot of oscillations and intermittent stuff going on. Honestly, once I learn a little more about my scope and how things interact, I can do some tweaking in the driver stage to improve. I also have a new signal gen since that above post which helps. 

One thing I noted that might or might not be contributing to the weirdness is the power transformers. I ordered the kits at different times, and while the specs are the same on both transformers, the 2nd trans has slightly lower voltage out, by about 10-15v B+ I recall. As a result, I cannot get quite the same power output from both amps, the 1st is 15w and the 2nd is 14w. Anyway, I'm no super expert and cannot go into theory like some of those guys over at AK, but I can cut and paste, tweak and usually get something sounding about right. Anyway, stay tuned. I am still learning.