[TV MAN]

I just finished some more power testing, and also used those testers on the sides of my head. Soooo - I tried several different sets of speakers and my PAT preamp. They both sounded about the same, pretty quiet and clean ... than is, until I really cranked it. Now bear in mind, even tho I'm an old timer (kinda), I like to feel my music as well as really hear it. That said, this should explain why I've blown a lot of foam speaker surrounds and tweeters. Sooo - back to the test. The 1st amp built sounded pretty OK up to clipping. That's where I backed off just a bit. The 2nd build, well, it lacked after just a shade over what I call 'cranked'. In fact, it sounded awful and fell totally flat!

Soooo - back on the bench! On my scope, I could only get about 21vPP before it clipped. I checked the other and it didn't clip until about 31v. I also tested my kit amp using the 6P1 version of the 6BQ5/6V6. and it peaked at about 33v before clipping. Woah! What?

So, then I remembered I'd left the 4.7K screen resistors on there, which is about the only difference I could think of. So I swapped for 100R. Powered back up and the output raised to about 28vPP before clipping. Then I jumped them, and that brought it up to about 29.5VPP before clipping. So, those screen resistors DO make a difference, even if idle voltages aren't much lower. A couple things that could also attribute to slightly different power output (very minimal) is that the tubes in the 2nd amp are very slightly lower emission, and a little farther apart concerning matching, where the 1st amp tubes are dead on matched. The other thing is for some reason my B+ is very slightly lower on the 2nd amp. The 1st is 330v on the 6V6 plates, and the 2nd is about 318 on the plates. The 1st kit is a little older, purchased in '22, and the 2nd is purchased within the last couple months. The Power trans might be slightly different. I'll do some more checking.

I also checked the signal at the grid of the inverter tube just to see how much and where it clips. Well, it is solid up to about the 90% setting, which is well below the setting where it clips on the output. I didn't check the output grids tho. Later.

I'm not sure how accurate my PP readings are on my scope, but I did note that the freq response was pretty flat from about -25hz to 15k (which is the highest I went), so as of right now, I'm not sure about the power output. I do know they sound good now.