Yes yes ! Have to dig all over the net..lol

You got it!

Thanks!!

@@SkunkieDesignsElectronics, any given time

Yes, thank you

Glad it was helpful!

⁠@@SkunkieDesignsElectronicsStephe, that was absolutely brilliant - not just helpful. It wasn’t too technical at all (especially as you watch it back over a few times if you get stuck on the theory or the practical implementation). This is exactly what we would need to do whether designing or checking a a design for ourselves, so I’m really grateful. I’ve read worked examples of working out load lines plenty of times. but I’ve never designed any circuits - so that was all just theory for me in the past which makes it hard to remember. This was super interesting and useful, especially after following along to understand why this amp was performing as it was to begin with. One quick question if I may - When you re-worked the load line, using the 33k plate resistor for the driver tube, to get the bias current raised to where the tube is performing both in a more linear region of the curves, and also where the signal voltage swing (at 4Vpp, 1.4VRMS) becomes symmetrical (as it should be). Did I miss something, but the original bias point was at 6V, then on the revised load line you went from a bias voltage of 4V (at 08:49 in the video), so the signal swings down to -2V and up to -6V instead. Was that a small oversight, or did the other changes you had worked out also shift the bias point down from 6V to 4V? Or would we now need to make changes to the bias resistor to change it to 4V instead? I suppose where the load line ended up, swinging from 6V down to -4 and up to -8V would still have been symmetrical anyways, so no problem either way I guess, but it would be helpful for my understanding to just sanity check that please. Thanks again, Steve 👍 [Edit: Just watched it back again and I think I’ve messed up - the voltage on the Cathode is/was at 6V, so the bias point must be slightly more negative than that shouldn’t it? So maybe the first load line signal spread should have been from a bias point less than 6V? It’s late and I’m confused 🤯😂 - So if you could just clear this up please that would be a great help 🤞. Thanks again]

I easily could has said one phrase wrong. The original bias point was -6V and so the input grid would swing from -4 to -8. The revised bias point is -4 and would swing from -2 to -6. The plate load resistor moved the load line up out of the "heel" of the curves, the cathode resistor changes the bias point to a more linear part of the load line. Hope than clears this up.

Hi Stephe, No you didn’t say the wrong thing at all - It was just me having one of those ‘brain fart’ moments! 😂 I watched it all again and of course it makes total sense to shift the bias point down slightly from 6V to 4V to get a 1.4VRMS signal right where it needs to be where the swing each way will give a symmetrical output - which was of course the whole point - Doh! 🤯 Silly me. It was a bit late on a night when I first watched this and I kinda got all muddled up in my head and fixated on the wrong principle. Thank you again for clarifying and all your hard work 🙌

It's pretty complex stuff but once it clicks it's like "Ah ok, NOW I get it!!" And there is a little trial and error to find the ideal spot plus these curve charts are a guideline, sometimes in practice you have to play around some to get the voltages where they need to be.

Reisong A10/A12 was much easier to mod and the results are really spectacular. I think you can find a second hand for 200-250

Glad you enjoy it!

I recently did a video on output tube load lines. Honestly there is an easier way to figure out what output transformer to use etc. I'll go over that with this amp. Honestly, I'm still learning how to deal with PP stuff, not something I fully grasp fine tuning yet.

lol yes, thank you MP for making a mediocre product lol

Thank you!

These honestly aren't that small, they are the same size core as the 15W Edcor transformers. The only reason they would saturate is if they are defectively designed. Remember they advertise 15Hz - 30KHz frequency response.

@@SkunkieDesignsElectronics Well, that range sure appears rather fanciful, but maybe it's at +/- 20db :)

Glad you enjoyed it!

That sounds harder to me!

That is NOT the final changes, I say this multiple times. I have some other projects and reviews as you have seen being published, plus have some parts ordered. PLEASE be patient!

Looking forward to it Steph.