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VSSA Lateral MosFet Amplifier

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sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Lazy Cat said:
SSA is completely different situation. :yes:

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 ... :cool:
Click to expand...

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.
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Lazy Cat said:
SSA is completely different situation. :yes:

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 ... :cool:
Click to expand...

Bjt + jfet CCS will dynamicly have a zout of >1meg compared to 15k for the resistors . So dynamicly less bias current modulation.
 
Lazy Cat

Lazy Cat

Member
Joined 2007
As you know SSA has very capable CCS installed and overal performance is on top level. :cool:

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. :yes:

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. :wiz:
 
T

tinitus

Ex-Moderator R.I.P.
Joined 2005
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 ?
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Lazy Cat said:
As you know SSA has very capable CCS installed and overal performance is on top level. :cool:

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. :yes:

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. :wiz:
Click to expand...

Which resistors are thinking of when you say injection?

It is going to be a busy night.
 
Lazy Cat

Lazy Cat

Member
Joined 2007
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. :eek:
 
Lazy Cat

Lazy Cat

Member
Joined 2007
sonnya said:
Which resistors are thinking of when you say injection?

It is going to be a busy night.
Click to expand...

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.
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
tinitus said:
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 ?
Click to expand...

What i mention has no impact on steady State values tinitus. This means that you Can still hardwire it with a resistor instead ;)
 
sonnya

sonnya

Member
Joined 2001
mirand-audio.dk/?post_type=product
Lazy Cat said:
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.
Click to expand...

Know i see it. Correct the currentsource with the 15k is grounded and in the SSA and TSSA this currentsource is coupled Direct to the emitter and modulated.

There Will only be a small benefit of changing it to a ccs. Biggest advantage would be a constant current source regardless of supply voltage.

Nothing more to say on this matter.
 
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