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Old 25th December 2012, 09:15 PM   #141
sonnya is offline sonnya  Denmark
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Originally Posted by Lazy Cat View Post
SSA is completely different situation.

You have to read post #80 in this thread where I explained all three different possibilities to inject input bias current at this CFB topology. VSSA is different because current injection resistor is in between two AC grounds, so AC voltage drop on it is zero. DC voltage drop is high and almost constant so current is therefore constant as it would be CSS. See the idea ...
Yes i know. But it is basicly the same, the path is the same and only difference is that the emitter feedback resistors are ac versus dc coupled.

But what sounded Best on the ssa??? Dig into your memory and notes , Then you know what you should do.

I am know what i would do. The TSSA performs very Well with the ccs.
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Old 25th December 2012, 09:28 PM   #142
sonnya is offline sonnya  Denmark
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Originally Posted by Lazy Cat View Post
SSA is completely different situation.

You have to read post #80 in this thread where I explained all three different possibilities to inject input bias current at this CFB topology. VSSA is different because current injection resistor is in between two AC grounds, so AC voltage drop on it is zero. DC voltage drop is high and almost constant so current is therefore constant as it would be CSS. See the idea ...
Bjt + jfet CCS will dynamicly have a zout of >1meg compared to 15k for the resistors . So dynamicly less bias current modulation.
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Old 25th December 2012, 09:29 PM   #143
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As you know SSA has very capable CCS installed and overal performance is on top level.

TSSA has AC voltage drop on injection resistor which is as high as input voltage or as divided feedback voltage, so injection current is far from being constant. CCS is essential in TSSA.

VSSA has zero AC voltage drop on injection resistor.

I really decided to explore this basic CFB topology to the extreme, all combinations, all versions build, tested and listened to.
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Old 25th December 2012, 09:30 PM   #144
tinitus is offline tinitus  Europe
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hey, we are happy with anything that works well
going for the best is a different story
we know how that goes...it never ends
I personally hope it will be kept close to the present state where proto board and hardwire is still possible

any chance to use available drivers, instead of 'obsolete' devices ?
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Old 25th December 2012, 09:30 PM   #145
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Originally Posted by sonnya View Post
So dynamicly less bias current modulation.
If AC voltage drop on resistor is zero, where's current modulation than?
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Old 25th December 2012, 09:33 PM   #146
sonnya is offline sonnya  Denmark
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Originally Posted by Lazy Cat View Post
As you know SSA has very capable CCS installed and overal performance is on top level.

TSSA has AC voltage drop on injection resistor which is as high as input voltage or as divided feedback voltage, so injection current is far from being constant. CCS is essential in TSSA.

VSSA has zero AC voltage drop on injection resistor.

I really decided to explore this basic CFB topology to the extreme, all combinations, all versions build, tested and listened to.
Which resistors are thinking of when you say injection?

It is going to be a busy night.
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Old 25th December 2012, 09:38 PM   #147
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No AC on resistor means no current modulation. Why do you think all SIM-s at the beginnig of this thread showed H2 -100dB with current injection resistor only? No AC - no modulation - constant current. Resistor only makes it, just imagine what would happen if we go complex on VSSA. CCS would rocketed performance to -130dB and less.
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Old 25th December 2012, 09:42 PM   #148
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Which resistors are thinking of when you say injection?

It is going to be a busy night.
In VSSA sch both 15k are input stage's current injection resistors, located between two AC grounds. Feedback AC ground enabled with 10uF plus 2,2mF, rails AC ground enabled with all capacitors to GND, ripple in front-end set to minimum as we use resistor-diode-capacitor-GND serial link.
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Old 25th December 2012, 09:45 PM   #149
sonnya is offline sonnya  Denmark
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Originally Posted by tinitus View Post
hey, we are happy with anything that works well
going for the best is a different story
we know how that goes...it never ends
I personally hope it will be kept close to the present state where proto board and hardwire is still possible

any chance to use available drivers, instead of 'obsolete' devices ?
What i mention has no impact on steady State values tinitus. This means that you Can still hardwire it with a resistor instead
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Old 25th December 2012, 09:53 PM   #150
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Originally Posted by tinitus View Post
any chance to use available drivers, instead of 'obsolete' devices ?
Yes, if they're capable as the ones from sch. Not so easy task these days.
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