I'm just discovering your channel and it's really great! I went through the 10 first videos redoing calculus and playing with LTSPICE. This is absolutely perfect. Very well explained. So a great thanks for sharing .. I will continue to go through your videos.
I'm glad to hear that! Your feedback is greatly appreciated, sadly later I've been super busy with work so I'm unable to do more videos for a while, but comments like yours push me to continue doing my best to share as much knowledge as I can. Thanks!
Dude, this is absolutely priceless playlist , thanks a lot. Please explain jlh 1969 design in one of your videos, really can't wrap my brain around it. Pls ,pretty pls
First of all, loved your videos! I learned a ton! THANK YOU I have a question: Why do you not take the feedback for the common emitter stage from its output like you did in your introduction videos, but rather you take it from the output of the Emitter Follower? What would change if I connected R8 to the output of the CE instead? Cheers!
Sorry for taking so long to reply. I'm really happy that you've enjoyed the series and learned a lot from the videos. That's the idea behind this channel. About your question: The idea behind using feedback is to linearize the circuit in order to reduce distortion and improve the output impedance, since the feedback network will make sure that any changes in the output that are "different" from the input get nulled out. Taking that into consideration you'll always want to make sure that you take the feedback from the "furthest" node possible, that way the feedback circuitry will attempt to linearize all of your stages. If you had connected the feedback network to the output of the CE it would still work, since the next stage is just a buffer, but you wouldn't get all of the benefits of the feedback since the buffer will introduce a bit (very little) of distortion, but most importantly it'll have a slightly higher output impedance without it, which may increase distortion when used with some headphones.
i think you could improve your THD on highs using a inductor in parallel with a resistor on exit (accordingly with my trusty free app cellphone inductor calculator, 2uH inductor with a 10R). i noticed you removed the oscilation by making a filter to transistor base but didn't filtered at exit... btw, i've never get why they use this inductor//resistor on output stage. in theory i get it, but i didnt learned it. what a upset tweeter you will have XD
That would indeed help with the oscillation problem, but that in conjunction with the Zobel network at the output would be a bit of overkill, also the a capacitor is easier to source than an inductor, so it's preferable to use the capacitor. Those types of filtering are usually more suited for higher power amplifiers, which need every extra bit of filtering in order to help taming their highly reactive loads.
Dear i want to build similer circuit but in the end of video you said its THD Is 0.065 for mobile hand frees now i am confused that should i build it or not and what will be the sound quality on hand free
Not on this one, but I'll be using them in a future project that involves lighting, I'll probably start on it as soon as I finish this one, since it's a simpler project it'll probably be a "shorter" series of videos.
You'd have to adjust R5 to balance back a 12V midpoint at Q4 Emitter, probably near 13k. You'd have to double R4 to bring back the Q2 current generator to 2mA, near 20k. You'd have to double R10 to bring back the Q7 current generator to 70mA, near 9k. And you'd have to mount those output transistors Q6,Q7 on some kind of heat sink to dissipate the extra heat due to increased power consumption. Other than that, I see no reason why it shouldn't work at 24V.
