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Old 17th December 2004, 12:48 AM   #11
thanh is offline thanh  Viet Nam
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mikeb! your ltp use two resistor load but geiirin only uses one resistor load
do the result become better ?
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Old 17th December 2004, 05:49 AM   #12
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Hi, GEirin,

Nice idea. Whats the concept of using double bootstrap in the first place? What do you wanto to achieve?
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Old 17th December 2004, 09:23 AM   #13
MikeB is offline MikeB  Germany
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Hi thanh !

With the 2 resistors in LTP the RC is doubleeffective, in theory...
I think 100p from vas to -input is way too much, try 10p...
You also need caps from vas to gnd. (best with RC)
And it seems, in real world bjts are much slower than in sims, and
capacities between wires changes a lot...

Mike
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Old 17th December 2004, 11:31 PM   #14
thanh is offline thanh  Viet Nam
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thank mikeb!
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Old 18th December 2004, 09:27 AM   #15
GEirin is offline GEirin  Argentina
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Hi all.
Thanks.

MikeB.
My amplifier is very old (1974?), quasi-complementary desing. The sound is good. I need to improve. Recenty, I look Aksa, P3 and other amplifiers, ( no constant current source) and i think, my amplifier is good?.
Ok. Yes, is quasi-complemtary. And i think in complementary. Also in class AB.
My amplifier had no miller cap, is good?
My amplifier had two bootstrap, is good?
What is your opinion?

Lumanauw
I am Industrial Designer, no electronic engineering. I believe that the amplifier is original Philips design.
My amplifier had: 50W, +/- 35V. T11 and T12 2N3055.
My idea is to change output transistors.
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Old 18th December 2004, 09:45 AM   #16
GEirin is offline GEirin  Argentina
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Hello Thanh.

R13, R11,C7 and R7, R8, C8 are double bootstrapping.
R24, R17, D3, D4, T5,6,7,8 are protections circuit.

Guillermo Eirin
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Old 18th December 2004, 12:13 PM   #17
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Hi, GEirin,

I also found out that bootstrap sounds better than CCS. Is this why you want to make it double bootstrap?
I have "suspicion" that double bootstrap that you draw cannot make positive signal well. Negative is no problem, since it is drawn by VAS transistor. But how about up positively?
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Old 19th December 2004, 10:32 AM   #18
GEirin is offline GEirin  Argentina
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Hello Lumanauw.
Many amplifers has single bootstrapping. I want to learm why my amplifier has double bootstrapping. Pros and cons.
Guillermo Eirín.
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Old 21st December 2004, 08:27 AM   #19
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hi GEirin
first impressions are nice as I look on schematic
I don't think you need a miller cap; C6/R1/R4 circuit seems nice way to keep the amp stable, also R2/C2 is useful, so you can have no oscilations at all
But i would skip R9/C9 - unneeded phase distortion is never good.
About the second bootstraping cap- I don't see a point in using it as voltage-amplifying transistor is opened and can give much current. The compensating cap is useful, when this transistor is nearly 'closed' (sorry for my english). But maybe this makes the situation better.

As your main question was about copying this or not:
my answer is: yes, after some changes you will have much fun, good sound and SATISFACTION of having self-designed amp.

What I would change:
skip R9/C9 as mentioned before
use non polar 1u good quality C1
use complementary output with some modern bjts
mirror T1,T2,T3- two complementary dirrirential stages with double bootstrap....may be interesting, don't you think?

regards
cheers
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Old 21st December 2004, 02:06 PM   #20
GEirin is offline GEirin  Argentina
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Hi Darkfenriz.

Thank you for the explanation. What is your opinion the C5?

Thank you for the recommendations. But think to improve the transistors, and to change quasi-complemtary for complementary design.
Now, I think other new amplifier. A symmetrical amplifier with double bootstrap? humm.....

Guillermo Eirín
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