high performance 25W PowerAmp

It was proposed to use a magic 5.1k unicorn resistor to stabilize the amplifier,
No!
however that resistor has a negative effect on THD.
Wrong conclusion /view!


Nevertheless,
well done Bernhard 🍭

Let's have a beer together (I' ll pay),
HBt.
:cheers:


#
Have you tested your suggestion with a jump and oscilloscoped its response? Do that!
 
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And what´s that?

I did AC analysis with the magic unicorn by the way and used the slider to see the impact of it.
The question of the meaning of the 5k1 should now be clear even to the most nagging questioner; this placeholder and reminder stands (among other things) for the final clarification of the question of stability. Without considering the Bode plot, one is unfortunately blind in this eye - or without the time domain.

5k1 -> transformed or morphed into [100Ohm+j(1/ Omega * 10nF)] - clear from the beginning.
for better illustration purpose only


with
1719045988828.png


&
without
1719046873917.png
 
None of this is a problem for the last unicorn, let's take a closer look at the first original working diagram ..!

1719476598999.png


At first glance, it is noticeable that the simulation results of MC12 differ significantly from those of my old Spice - could this be due to the models used?
Anyway, above we see the 5k1 representative with a real infinite number of ohms.

1719477617624.png


In fact, you are absolutely right, as we can see it - from 100kOhm to 100Ohm.



#
And now let's look at the case where the said fiend moves within the limits of 10kOhm to 5kOhm:

1719477971397.png

Oh dear,
from this perspective, the interjection seems to be nothing more than nitpicking (to put it kindly!).

Now let's connect a small ceramic 22pF capacitor in parallel to the 100kOhm feedback resistor and thus limit the band! I'm already very excited and looking forward to MC12's result. The tension is deadly :eek:.

1719478559453.png


Checkmate!
 
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1719478862991.png

Overview with Ck=22pF.

1719478989135.png


Dear Bernhard,
could you please take my advice and stop being so opinionated.

There's no point at all. But if it helps in any way, I absolutely agree with you in principle - let's look at the limiting cases of infinity and zero:
as soon as your zero can be regarded as decisive in relation to infinity, i.e. is practically zero with n ohms (always in relation to infinity), you are 100% right. Only in the applied context /task are you talking rubbish.


I'm sorry, but that's the way it is - by the way, we're definitely talking past each other.
As an aside: I don't jump back and forth between different dimensions and component selections in every simulation, but you seem to prefer to do this - which makes any comparability and illumination of your theses impossible.


Bye, bye,
HBt.
 
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Does MC12 use correlate with the frequency of disputes? One might have the impression.

#
It was quite clear that the opposing party would pounce on the unicorn - and not only fall into the trap (that they have set up themselves), but also completely banish the basic analog circuit of an adder using an operational amplifier (as a synonym) from their minds.


But the bottom line is: trust your reasoning and build a test circuit, measure and determine all relevant parameters!

What's more, since MC12 often deviates significantly from PSpice in some places - whether this is important or nothing more than the parameterization and the models ... who cares ?
 
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🧙‍♂️

@Bernhard

Basically, I think a pertinent and well-founded exchange of ideas among experts is great, but I often find it difficult to understand your motivation and commitment in this and other threads, especially since you actually have no interest in this circuit and topology (as you yourself wrote here).


In plain language, this means that you will not dare to do a test setup.


Would you like to give us, little magicians who believe in unicorns, an insight into your art, your SuperDuper - reveal the schematic of your already (through other threads, spun ...) real existing, domestic amplifier?


(Suddenly)
I feel very small right now,
HBt.

🦄
 
In my simulation, the phase looks very different,
I know; Bernhard, I think the origin probably lies in your *.cir back and forth.
can you post the .cir ?
I'm not sitting at the computer in question at the moment, but basically it's the cir you originally provided, I just worked with it, nothing more.
Maybe I changed models, it's possible. While at home I use the models from Bob Cordell, Zetex, Siemens, Philips and OrCAD ... etc.

I'll be back in a week, but is it really that important? The solution is always obvious and you sit down together at the PC and use the tool of your choice.
And because, logically, we can't do that, that's where the problem lies - at least most of the time. I have experienced and observed this phenomenon countless times in my professional life.

Don't you agree? Or is narrow-mindedness and the know-it-all attitude more plausible?

That would be a shame and an absolute waste of time, but I don't want to have to assume that.

PM is possible at any time, only this time you have to unlock the channel (open a chat), I have deleted and blocked all channels open from my side.
So, if you no longer want to reject this option, it's up to you. Or publicly, with the tutorial option /thread I have activated, the ball is in your court.

Although the whistle had already been blown.

best regards,
HBt.
 
A little foretaste - quick pictures of the test panel /pcb


The drill was blunt, as you can easily see, but the snot is installed - components . Soldering will be done tomorrow and then the test will start slowly.


Experimental archiological greetings from the excavation site,
HBt.
:wiz:🍭
(let's see which BJT burns out first?, I have a suspicion!)
 

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hbtaudio - I had thought this was just a simulator exercise, but now I am impressed that you are building the amplifier.

In addition to the ripple sensitivity, I see two more problems:

* The bias current depends on the Is of six transistors and two diodes. Some means of adjustment will be needed.

* Removal of the shunt capacitors means that the amplifier is entirely dependent on transistor junction capacitances to bring down the loop gain. Capacitors may still be needed.

Be careful and good luck!
Ed
 
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