Insane frequency response!? Or just my mistake...?

[keantoken]

I have to blame this design on mikeB, of who's SymAsym design I have been obsessed with for quite some time and can reproduce it perfectly from memory!

It happened quite strangely... I was dinking around on an OPamp idea. I had removed a feedback path and freaked when I saw the AC plot. Almost perfect from 0Hz-100kHz! The phase wasn't too bad either - -10deg offset @ 100kHz! I am not quite sure about the arrangement of Q3-Q6, but it helped the frequency response and didn't choke anything so I left it in there (immature - I know, but please bear with me as I would like an explanation as to what this does).

The output from 0.01V input was around -1.5db. The FFT wasn't horrible @ 1kHz, and I believe that there usually wouldn't be much a difference in distortion if there are no frequency filters and the response is as perfect as the AC graph implies.

I tried adding a few RF filtering caps but it didn't affect the response much at all. The only explicit filter cap is in the input arrangement.

I have attached a ZIP file containing all of the models used as
well as the netlist and .asc (for LTSpice) and a few screenshots.

The output pair I believe is a waste of power, but they were the only ones that I knew could handle it (yes, my knowledge of the transistor varieties is very limited...). Any suggestions?

Here is the zip:

[Elvee]

Hi

It is essentially a load of ********, but at least it shows one interesting thing: improper or misunderstood use of simulations can give weird results.
LV

[MikeB]

Keantoken, -1.5db output from 0.01v input is just a gain of ~84, not much compared to the original 32000...
I do not see any sense in q3-q6. Try to explain the voltage at the bases of q4/q6.

Mike

[ilimzn]

Still cluelessly throwing components at a simulator, I see... keep it up and you'll be a high-end audio guru for sure

What is the purpose of Q3, Q4, Q5, Q6, R1, R2, R5, R6, R7, R8?

What is the purpose of R23 and R24?

The roblem with the output stage is not your choice of transistors but your choice of topology, what is it designed to accomplish? (Currently it's only wasting amazing amounts of power)

[keantoken]

Never mind...

I thought the idea for the output stage was interesting because it makes sense to me that if there were a reactive load on the emitters of the transistors, or in some way a fluctuating load, then the biasing would be affected by not just the input signal.
This is why I chose the output to be emitter-follower. That way, if you have an unstable load, the output pairs still have a somewhat stable bias. Maybe I'm wrong. Maybe every single thing I've learned about electronics up to this point is wrong. Maybe Q3-Q6 work as negative feedback. Maybe I'm wrong again.

You may conclude from this post that I just don't care, or that I don't want to listen to anybody, or that I just like to see wavy lines on my computer screen. If so, maybe your right. I have taken tons of discrimination from other kids at school, certain family members, and have had teachers go cold on me because I just lack the social skills. Everybody seems to think that I don't care or that I hate everybody else or something like that. Maybe their right. Maybe I'm a horrible person trying to stay in my own little world where everything works like I want it to. Maybe this is because I never tried to talk to anyone and never tried to fit in with everybody else.

But during this whole time, my family stayed with me. Even though I mortified them sometimes, they didn't stop trying to help me and didn't try to push me away when I needed them the most. My brother hit me sometimes, and me and my mother were always at each other's throats, but they stayed with me and still keep me going to this day. I believe that this is the sole reason that I am not trying to rip my hair out right now or hurt someone, or quit out of DIYAudio. The one thing I do know is that I won't give up because almost everybody is derogatory at me. I have gone through rough times and know by now that nobody else's decision can affect my life as much as mine. Maybe I have made a bad decision somewhere. Maybe I should just stop trying to be more than what others see me to be. But I won't. I don't know how to give up, at least I hope so. Because I know that giving up could just be my second worst mistake. I try not to let what others say affect me so much, but there is only so much I can do to bottle it up inside, and eventually, it all has to come out. This is why I am speaking now, and not deciding with my feet later.

And now, despite the unsettling ongoings of my recent discovery, I will wish you all a Merry Christmas, because you are all annoyed for a good reason anyways.

Merry Christmas!



- keantoken

[darkfenriz]

keantoken

Keep on, man !

One has to make mistakes on his own and draw his own conclusions.
If you walk your own paths, you can end up with something great.

There's nothing bad in learning or having yet insufficient knowledge, but that's good to see peculiarity (but not misanthropy) and perseverance!

Reading a book or two wouldn't harm though

cheers

[keantoken]

Thanks, Dark.

About books, I'm hoping to get one as a Christmas present. There isn't really a technical bookstore around and we don't have a credit card that we aren't afraid to use. I suppose online resources might be enough, but they just don't beat a good book.

- keantoken

[rephil]

Hi keantoken,

let us look at it in the positive way : simulated circuits don't smoke, explode or destroy costing components. Thus all is OK !


Keep on man.

Merry Christmas to you!

[MikeB]

Keantoken, don't get depressed, just learn how to use electronics, try to understand it.

Mike

[ilimzn]

Originally posted by keantoken
Never mind...

OK, let me re-arrange this a bit:

You may conclude from this post that I just don't care, or that I don't want to listen to anybody, or that I just like to see wavy lines on my computer screen. If so, maybe your right. I have taken tons of discrimination from other kids at school, certain family members, and have had teachers go cold on me because I just lack the social skills. Everybody seems to think that I don't care or that I hate everybody else or something like that. Maybe their right. Maybe I'm a horrible person trying to stay in my own little world where everything works like I want it to. Maybe this is because I never tried to talk to anyone and never tried to fit in with everybody else.
But during this whole time, my family stayed with me. Even though I mortified them sometimes, they didn't stop trying to help me and didn't try to push me away when I needed them the most. My brother hit me sometimes, and me and my mother were always at each other's throats, but they stayed with me and still keep me going to this day. I believe that this is the sole reason that I am not trying to rip my hair out right now or hurt someone, or quit out of DIYAudio.

Oh please DO get over yourself. Life is not a walk in the park, and i think most of the people here on this forum could say the same you did of their younger years. In other words: welcome to the club.
no-one that has posted in your threads is trying to make you quit, not even the persons with the less than favorable comments. I will spell out why your posts are frustrating a bit later on, so that there is no more confusion.

Maybe I'm wrong. Maybe every single thing I've learned about electronics up to this point is wrong. Maybe Q3-Q6 work as negative feedback. Maybe I'm wrong again.

I would suggest that you read carefully, once again, what I have written, and try to answer, carefully, and sincerely, at least one of the questions in my post. Not for me, but for yourself.
Then tell me: do you put together circuits to MAYBE work, or do you throw together parts in hopes of figuring out what it will do (which, i admit, can be fun), or do you actually have a purpose in mind beforehand?
You mention Mike's symasym, and knowing it by heart. I would point your attention to a nugget attributed to one Albert Einstein, who also came from a disadvantaged background, and was made fun of: 'Every fool can know, the point is to understand'.

And you know what the frustrating thing is about your posts? Well, there was a whole thread where many of the regulars on this forum practically bent backwards trying to make you understand the basic concepts, so that you could leap forward, without doing it head first into concrete. Yet, over and over, we get posts from you with complex circuits that have parts put together without a discernible purpose (or are we all really stupid - as you would say, maybe we are), but never a post with the simplest circuit properly biassed. So, our considerable efforts seem to continue to be for nothing. Proof? Well here it is:

This is why I chose the output to be emitter-follower.

An emitter follower is in it's simplest form A SINGLE TRANSISTOR. Yet, you have not managed to do even that right, because, guess what, the output in your schematics IS NOT AN EMITTER FOLLOWER!!!

So stop whining and complaining, do your homework, and, eventually, try to build a SIMPLE circuit, just to see how well it will fit with the simulator. BTW there is a TON of stuff on the net (which you seem perfectly capable of accessing!), and there IS a reason they start with the simple stuff.
In other words, no-one wants you to stop. But we do want you to start properly.