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@@StealthParrot Thanks for watching and commenting. The first transistors were alloy junction devices. Dopants were bonded to germanium which formed the junctions. Not a very effective way to do it but easy. Now it’s usually done via diffusion of vaporized dopants at high temperature in a vacuum chamber. Hard to explain in a comment but maybe one day I’ll try to get back to the facility at Penn State and do a nice video on this. If all my contacts haven’t retired by then!! 👍🏻

@rlibby404 thanks! Yeah, I need to mic the amp and get higher fidelity with the sound. I’ll work on that. The analysis methods are detailed in the videos right before this one. If you go back to video 60 that’s where I start introducing triodes. Between there and here I cover all the basics of triode and pentode circuit design and analysis.

@@ChaseNoStraighter thanks!! I will give that a try next time I do another video like this. I’m pretty much not experienced at video production at all so I’m figuring this out as I go. Thanks for watching! 👍🏻

@ you are doing fine. You are doing the experiment that I have wanted to do for a long time. You could also look in close at the side bands as there maybe some 120Hz AM which may actually sound good.

@@bradatherton9369 that would be interesting. Maybe one of these days… Thanks for watching! 👍🏻

@@PorchBass you’re welcome! Thanks for the feedback 👍🏻

@@petertimp5416 thanks for watching! 👍🏻

I’ve done this analysis a few times, with h different tubes (for example, I did one on the Facebook page for Electronics for Guitarists” and got the same results. I will talk more about this topic again soon. Thanks for watching! 👍🏻

@@zazamarco235 thanks for watching! Yes, the screen grid can be used to form a VCA. Eventually I plan on doing some videos on VCAs and amplitude modulation principles in general. That was one of my favorite topics to cover when I was teaching. I will get to it so hope you’ll stick around. 👍🏻

@@jimgibson9811 Roger that! 👍🏻

You are welcome! Thanks for tuning in! 👍🏻

I will try to address this one of these days. There are so many topics I’d love to cover more deeply. Hopefully I’ll get to them all eventually. 👍🏻

@@beebeangelmovies thank you! I plan to do several amplifier design/build videos eventually.

@@yqz318 PSpice

I use good old Microsoft Paint. I created all of the symbols years ago for illustrations for textbooks I was writing so most of the hard work is already done. It’s not the most efficient way to do schematics but they look 100x better than the crap that typical schematic editors (PSpice, etc.) produce. I’m sure there’s a better program I could work with, but at this point it’s not really worth the effort to change.

@@longduonghoang9512 you’re welcome!! 👍🏻

Unfortunately there aren’t many good references explaining this stuff. I explain how the characteristic curves can be used to estimate gm, rp and mu in Video 68. I might do something on deriving curves in more detail sometime but that will be a ton of work and I’m not sure how many people would watch it. The best solution would be to run curves on a curve tracer like a Tektronix 570. But unfortunately those are almost impossible to find these days. Anyway thanks for watching and hopefully I will address some of the topics you would like to see in upcoming videos 👍🏻

@@sahhaf1234 not this time. I’ll be covering negative feedback explicitly later in the series, particularly when I get to op amps.

Thanks for the compliment! I hope you enjoy the rest of the videos 👍🏻

Thanks!! I will be covering op amp theory when I finish vacuum tube amplifier stuff. Hope you’ll stick around until then. It will be worth the wait 👍🏻

@@Linguae_Music 👍🏻

@@petersfatbelly I wish I could post schematics in the comments. When I eventually get back into solid state circuits again I’ll post some related circuits which should help. Thanks for watching 👍🏻

@@You_T_Channel thanks! 👍🏻

Those were the good old days! Thanks for checking out my videos 👍🏻

@@mrobson6052 👍🏻👍🏻👍🏻

Thanks! I’ve got several more in the works 👍🏻

Thanks. Glad you found the information useful 👍🏻

@@davidluther3955 roughly the same as for the usual common cathode and cathode followers.

Thanks!! I know I get pretty deep into the weeds with the math and more advanced circuit analysis, so I appreciate you hanging in there with me. My most recent videos are well into tube amp analysis and design which I think is some very cool material. Hope you continue to watch and find it worthwhile 👍🏻

@ I actually appreciate a lot the fact you go deep in maths. I’m currently studying sound engineering, specializing in audio electronics and signal processing, your videos have been helping me a lot in understanding better all of this and you can be sure I will see them all! Hahaha Greetings from Chile my friend, and thanks again for your work😄

In the context of typical amplifier applications, a small signal is a signal that allows us to use the linearized behavioral model of the device (BJT, FET, tube or whatever). We assume that device parameters are constant and things like clipping don’t occur. A large signal is one that causes the amplifier to behave nonlinearly- usually in the form of clipping. If we are dealing with circuits that are inherently nonlinear (log amps, analog multipliers etc) then we make other assumptions.

Yes, Vg = 0 V because Ig=0. But VGK is negative: K is positive with respect to G, because of the drop Ip*Rk.

Vpp is modern notation for the positive DC supply rail. The old school notation would be B+. The notation I use corresponds to that used in BJT and FET circuits (Vcc, Vee, Vss, etc).

@@davidluther3955 not sure what you mean. These are basically the same equations we used for BJT and FET amplifiers.

@@leandrocarg it would reduce mu and it increases response to power supply ripple. Distortion will increase because screen current varies with plate current, but variation in screen voltage causes changes in mu, gm, rp which results in intermodulation distortion. Bypassing the screen reduces this effect.

@@Electronics4Guitar So you are saying distortion rises because of poor PSRR? Shouldn't this contribute to hum instead of distortion? It's noise after all. I know that this NFB would reduce mu and rp, lower rp means more PS hum drop on Rp!!RL (a simple voltage divider), but I don't get why should the distortion figure be affected.

@@leandrocarg if you change the voltage on the screen the gain is affected and not only that, the level of distortion changes, eventually reaching very easy to hear levels - but you can measure it before it can be heard as I did easily provided the equipment. It starts as negative feedback as you say. But it isn't a linear phenomenon. So, yes, it affects distortion, in both directions, depending on the entity of the ripple and starting voltage.

I haven’t seen much detailed information on supply sag, it it is a popular topic in guitar gear forums. Using relatively high value resistors in the pi filter can cause sag, but it also depends a lot on the amplifier topology. Class-A amplifiers have a nearly constant current drain regardless of volume level so sag isn’t really a possibility. Amps with class-B output stages are more likely to induce sag. I’ll cover this topic in detail in a future video.

@@georgetrax9922 I’ll be doing pentodes soon 👍🏻

@@SpinStar1956 thanks! I like to present circuit analysis and design succinctly, with all the gritty details and as little hand waving as possible, and without childish antics (like some content creators that I won’t mention by name). Also, you are right. I should expand my resistor assortment for the experimental circuits (just ordered some on Amazon). I do order precision resistors when I build amps, effects, etc. though. Anyway, thanks again for the feedback and hopefully you’re subscribed 👍🏻

Yes. The negative sign just indicates that the gain is inverting. I will probably present the solutions to the problem in the next video. Hopefully in a week or so.

They’re hard to read even at full size. The best thing to do is print some out from the PDFs online and work along with the video. I am working on cleaning them up but it’s going to take a while.

@@peterbulanyi1708 several factors. In most applications we want the Q-point centered on the AC load line for maximum unclipped output. In a guitar amp we might choose this location or a location that produces asymmetrical clipping. As long as the load line is within the SOA it’s all good. There are subtle things to consider too but I’ll get to that in a few videos.

Pentodes are on the menu!

@@davidluther3955 probably sometime after I finish all of the audio related stuff. I will get into tuned circuits, basic RF amps, etc eventually but it won’t be for a while.

Thanks!! Yeah, sometimes just using a general principle like this is really helpful. I try to present these ideas and rules of thumb, and also show how they are derived. Thanks for watching and I hope you like the rest of the videos too 👍🏻