that analysis is really cool. I build a similar amp (2F2A basically a champ with added tone, which I also added a presence on the feedback loop and a grid resistor to the power tube). One question I asked myself if the circuit is designed to work at 286V nominal, does that mean the voltage swing can go close to ~600V on the positive side? (thinking about cap rating to use), or am I not seeing it right and 286V is the peak on the positive side (the tube chart do stops at 400V)? Was the circuit actually designed to drive the tube into saturation or was it a 'happy accident' and it was intended to be operating nominally without driving the tubes into pretty harmonics? (can the harmonic saturation 'quality' be measured other than an FFT showing order peaks?) Finally, can we get even more harmonic saturation by tweaking the circuit even further (or is it worth it)? I'm an ME with interest in audio circuits, so these videos are a golden mine!
AARON, Can you make a video lesson about "Tweed Mixers" they are called other terms but fender amplifiers use them but using either 1 halve of the 12AX7 or using both plates that get tied to a tweed mixer. This causes signal to noise ratio issues because when you tie two different gain stages of plates to the same DC voltage node it creates noise because that two plates are from different gain stages. You will see this often in 80s and 90's fender amplifiers I'm guessing because of bad engineering but when tieing two different 12AX7 plates together to the same DC voltage node will cause noise issues causing the signal to noise to get worse which I'm not sure why that is but I think this is why they used "Tweed Mixers" which they are called.
The plate current extrapolation trick is nice, but I wonder how close you would get by just linear extrapolation starting from 200 V and 250 V if you want to reach 286 V? Not sure if you had multiple data points to start from in all cases though, then that extrapolation trick is definitely useful.
I love all of your videos they are so helpful
Thank you for your kind words!
that analysis is really cool. I build a similar amp (2F2A basically a champ with added tone, which I also added a presence on the feedback loop and a grid resistor to the power tube). One question I asked myself if the circuit is designed to work at 286V nominal, does that mean the voltage swing can go close to ~600V on the positive side? (thinking about cap rating to use), or am I not seeing it right and 286V is the peak on the positive side (the tube chart do stops at 400V)? Was the circuit actually designed to drive the tube into saturation or was it a 'happy accident' and it was intended to be operating nominally without driving the tubes into pretty harmonics? (can the harmonic saturation 'quality' be measured other than an FFT showing order peaks?) Finally, can we get even more harmonic saturation by tweaking the circuit even further (or is it worth it)? I'm an ME with interest in audio circuits, so these videos are a golden mine!
AARON, Can you make a video lesson about "Tweed Mixers" they are called other terms but fender amplifiers use them but using either 1 halve of the 12AX7 or using both plates that get tied to a tweed mixer. This causes signal to noise ratio issues because when you tie two different gain stages of plates to the same DC voltage node it creates noise because that two plates are from different gain stages. You will see this often in 80s and 90's fender amplifiers I'm guessing because of bad engineering but when tieing two different 12AX7 plates together to the same DC voltage node will cause noise issues causing the signal to noise to get worse which I'm not sure why that is but I think this is why they used "Tweed Mixers" which they are called.
I recommend checking out Richard Kuehnel's book on the Fender Deluxe (well, its many variations).
The plate current extrapolation trick is nice, but I wonder how close you would get by just linear extrapolation starting from 200 V and 250 V if you want to reach 286 V? Not sure if you had multiple data points to start from in all cases though, then that extrapolation trick is definitely useful.