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HiFi (Chifi) tube amp build - but my own design.
#53

I finally have some numbers. It took watching a few YouTube videos and measurements to get there, but the tally is in. My scope IS accurate, which I confirmed with my Fluke. With my 1st tests on the 2nd amp, nothing was adding up or making sense. Now I know why. Never would have imagined the G2 resistors would have made that much difference, but they did! So, I corrected that and did some more tests and this time things made sense. My scope showed right around 30VPP, which I divided in half, then X .707, which gave me about 10.6v, then squared and divided by 8. and that gave my right at 14w. I confirmed the RMS voltage with my Fluke at 10.65 and used the same formula. This makes sense since I built the amp to push about 15w. So, it's doing close to what it should. With the 4.7k screen resistors, it was only pushing about 8w! So, no wonder it sounded so lousy when I pushed it. It sounds much better now. The 1st unit pushes 31v, which puts at at 15w. It's kinda hard to get an exact reading because the level control is stepped, but I can also adj the signal generator too. But, it's close, and about what a pair of 6V6s are suppose to put out.

 A note: The PP kit amp put's out about 17w (33vPP). It DOES sound just a little stronger when I push it. It's actually rated at 12w, but I think since our line voltage is higher than 110 that it raises the B+. It could also be under rated.

My scope is just a little hand held unit and it's kinda hard to see things very clear, but I can see when the signal starts clipping. . I've got my eye on a new one with a bigger screen  that I may pull the trigger on. This is still an experiment. More to come.

Edit: Mike, they are on the primary of the OP tranny. I think the lower B+ on the 2nd amp build is cutting my wattage slightly. The output across the load is in the 10.6-11v range A/C or 30-31v PP

If I could find the place called "Somewhere", I could find "Anything" Icon_confused

Tim

Jesus cried out and said, "Whoever believes in me , believes not in me but in him who sent me" John 12:44


Messages In This Thread
462ron - by 462ron - 10-15-2024, 09:07 AM
RE: HiFi (Chifi) tube amp build - but my own design. - by TV MAN - 12-21-2024, 02:55 PM



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