How to choose a Topology

[Bakeacake08]

I have been re-reading @Teemuk's book "Solid-state Guitar Amplifiers," and it makes a lot more sense the second time around. Well, a lot more makes sense, that is. I don't have much time for projects, but I've been thinking of putting another one on the back burner: making a solid-state amp. I've been playing around with LTspice to test my understanding of theory, and it seems to be going pretty well (things mostly do what I expected them to do).

Anyway, the issue facing me right now is that I don't know how complex I should/need to go. After learning basic topologies, all the articles I read start talking about how to improve them, and it gets pretty complicated pretty quickly. I'm not against having difficult circuits to build, but what I'm wondering is at what point does it become so elaborate that it would make sense to just use an op-amp circuit instead? Or how simple can a circuit be made that is still serviceable? Put in different terms, if I were looking to build myself a car, I could make a hot rod and optimize the entire engine, but my '88 Tercel has all the basics and gets me around just fine. (And it got GREAT gas mileage. Too bad it was totaled a few years ago . . . )

I hope you understand what I'm getting at with my question. It seems that with tube amps (which is what I've been looking into mostly before now), there are only so many options, making it a little easier on beginners, but with solid-state designs, there are a thousand different ideas on how to put it all together, so I can't figure out what the "introductory" method might be.

And again, I can't recommend Teemuk's book enough. It's been a tremendous help so far on this journey, and I haven't begun to understand even half of it yet.

[Bakeacake08]

For instance, I've been playing around with this circuit this afternoon. It's three basic common-emitter stages with negative feedback. I basically copied a textbook example three times and added feedback. Neglecting tone controls and such, would this be good enough to drive an output stage? What problems might arise from this set up in real life (as opposed to the perfect linearity from the simulation)? These are the kinds of questions my mind is circling around right now. I'm also working on a simple long-tailed pair circuit, but dishes don't clean themselves (yet?), so that one will have to wait.

[Enzo]

get in there and make something.  Don't worry about developing it before it even exists.

Do you already solder well?  have you made other things?  If you want to get some idea of how the basic circuits work, make a little one or two transistor booster.   Your three transistor thing ought to at least amplify, so knock it out and see what it does.


If you wanted to build a car, you would not start by building a Tercel.  In fact you wouldn;t start by building a hot rod most likely.  You might start fiddling with a lawn mower to get used to tools.   My opinion only, but a whole amp doesn't sound like a first project. Preamp and power amp can be separate projects.

[Roly]

Oh I do agree - start out simple.  :dbtu:   (It is actually somewhat easier to make a circuit complex, but it's simplicity for the same result that is hard.)

Amps consist of stages and it is quite possible to sneak up on a full amplifier by building and testing a bunch of "Lego (tm) brick" stage modules then putting them all together.

Just a point about your fed-back preamp and tone controls.  You can't just slap a tonestack in the middle of this circuit because tone controls don't just alter the amplitude response, they also alter the phase response, and if you stick a tonestack in the middle of this preamp you may well find that it oscillates at extreme tone settings because the "negative" feedback becomes positive overall due to the added phase shift in the tonestack.


{having just done the washing up  }