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Old 27th April 2012, 07:05 PM   #131
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Originally Posted by homemodder View Post
The biggest problem here is the simulators, these always show baxandalls as oscillating, but in real life they can be stabilized. When you look at for example the thread you mention youll see every comment there is based on simulators, why didnt anyone actually go and build it. Does anyone really believe yamaha sell amps that are oscillating ?? I too have used traditional baxandalls with success in some circuits, theres another member here providing diy power amp schematics with baxandalls for builds, and none of his builders have mentioned any problems as yet, from what I gather 87 builds so far. Yamaha are still using them and many more recent Analog Devices opamps are full of them, look at AD quadcore technology.
Hi homemodder,

But if they can be stabilized in real life, then that same stabilization that is used in real life should be applied in the simulation. Then it had better be stable. I would never ever build a circuit that simulated in any reasonable simulation. I do know of cases where designers depend on real-life parasitics that may not be modeled in the simulation to have a stable circuit (either knowingly or not), but this is an unreliable practice.

We should not generally depend on real-world "imperfections" for a circuit to behave. Another example is building a circuit that is not happy if transistor beta is too high; just not a good idea.

At the same time, we must of course be cautious with simulators. For example, unless you go out of your way, all of the same type of transistor in your simulator will be perfectly matched. Some circuits might like this and work fine in simulation, but work poorly in simulation.

Finally, there are some circuits that legitimately will not work in a simulator unless coaxed to do so, and which depend on real-life "imperfactions". Multivibrators and some other classes of oscillators come to mind. In a simulator, you can stand a pencil on its end indefinitely, but you usually cannot do that in the real world.

Cheers,
Bob
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Old 27th April 2012, 07:30 PM   #132
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Default Multivibrators

Amen. BTW, this thread is about the super TIS and certainly not about minor and irrelevant details.
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Old 27th April 2012, 09:45 PM   #133
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Originally Posted by Edmond Stuart View Post
To all,

Regarding the circuit as shown below, I like to know whether anyone has seen this front-end before. If so, I'm curious to learn more about it and how it behaves in real life. More details can be found here.
(BTW, I'm still editing and updating that page, so it's not yet finished)

Cheers,
E.
Not due to you Edmond old chap...
This front end has been done before by Shinichi Kamijo here:

Evolve Power Amplifiers

Last edited by michaelkiwanuka; 27th April 2012 at 09:54 PM.
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Old 27th April 2012, 09:51 PM   #134
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Apparently, the author has never heard of an 'input-inclusive-compensation '. .
Actually, contrary to D. Self, there is no such thing.
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Old 27th April 2012, 10:00 PM   #135
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Originally Posted by michaelkiwanuka View Post
Not due to you Edmond old chap...
This front end has been done before by Shinichi Kamijo here:
Evolve Power Amplifiers
Great!
Please, provide a link to the schematic.
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Old 27th April 2012, 10:05 PM   #136
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Originally Posted by michaelkiwanuka View Post
Actually, contrary to D. Self, there is no such thing.
Do you mean 'input-inclusive-compensation ' is a misnomer?
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Old 27th April 2012, 10:20 PM   #137
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Great!
Please, provide a link to the schematic.
2SJ554/2SK2955 classAB SEPP power amplifier
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Old 27th April 2012, 10:22 PM   #138
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Do you mean 'input-inclusive-compensation ' is a misnomer?
Yes. The compensation described as input inclusive compensation by Self in linear audio is simply phase lead compensation with the output stage excluded.

Last edited by michaelkiwanuka; 27th April 2012 at 10:27 PM.
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Old 27th April 2012, 10:49 PM   #139
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Originally Posted by michaelkiwanuka View Post
Thanks Michael!
By now it's a bit late. So tomorrow I'll have a closer look to it.

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Originally Posted by michaelkiwanuka View Post
Yes. The compensation described as input inclusive compensation by Self in linear audio is simply phase lead compensation with the output stage excluded.
I already expected you would call it 'lead compensation' (I still remember the discussion about the compensation of Bob's HEC amp), but what's wrong with calling it 'input-inclusive-compensation'? In fact, the compensation loop does encompass the inverting input of the IPS. So.....

PS: Given the context of post 123, I think it was more than appropriate to use D.Self's own terminology.
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Last edited by Edmond Stuart; 27th April 2012 at 11:01 PM.
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Old 27th April 2012, 11:15 PM   #140
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Originally Posted by Edmond Stuart View Post
Thanks Michael!
By now it's a bit late. So tomorrow I'll have a closer look to it.



I already expected you would call it 'lead compensation' (I still remember the discussion about the compensation of Bob's HEC amp), but what's wrong with calling it 'input-inclusive-compensation'? In fact, the compensation loop does encompass the inverting input of the IPS. So.....

PS: Given the context of post 123, I think it was more than appropriate to use D.Self's own terminology.
Actually, I termed it Miller Input Compensation. So-called input compensation has been around forever, and has always had the property that it did not impair slew rate. I employed MIC in the early 1980s because it also does not impair slew rate and it does not reference either side of the compensation capacitor to the supply rail.

It is wrong to describe MIC as lead compensation, as Edmond has explained. MIC is fairly well-described in my book.

Cheers,
Bob
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