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Old 14th January 2009, 05:32 PM   #141
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Hi,
I would not make the voltage amplifying section complementary symmetrical.
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Old 14th January 2009, 05:41 PM   #142
catalin is offline catalin  Romania
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Quote:
Originally posted by AndrewT
C32 is too small.
It needs to be >= 22k/680r * sqrt(2) * 4u7F >= 215uF. Use 220uF.

C42 seems a bit big @ 47pF
R = 150 at output also seems big, only 8mA passing Q60 & 51.

Does the mirror load on the LTPs work when you have dual complementary VAS?

The 100 uF(still think that 47u is good) comes from low frequency ~5hz(not audible) => f=1/(2*3.14*R*C) ;= 0.16/(680*C);;;C=0.16/(f*R)=0.16/(680*47u)=5 hz.

C42 is calculated to minimise the noise band > pole at 154khz.(0.16/(22k*f)
Q60 and q51 working at 1mA ! not 8 . 2sc5171/1930 is working at 8-10ma. big input impedance for not oveloading vas => small thd . about the mirror ltp ...look at stochino's amp !
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Old 14th January 2009, 05:46 PM   #143
catalin is offline catalin  Romania
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Quote:
Originally posted by roender


Catalin,

May I suggest you to not reference CCS's biasing resistors to ground?
Try to make the input stage + VAS as much as possible a constant current compound stage.
Keep the ground as clean as possible and use a separated PSU for output stage, and for inputs stages a good ccs+shunt feedbackless PSU

Regards,
Mihai
An capacitor + another R to ground will be better ? or do you want to say something else ?
Thanks !
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Old 14th January 2009, 05:48 PM   #144
catalin is offline catalin  Romania
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Quote:
Originally posted by Lumba Ogir
Hi,
I would not make the voltage amplifying section complementary symmetrical.

Can you explain why?
Thank you
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Old 14th January 2009, 05:52 PM   #145
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Catalin, you are absolutely right about stochinos amp, but look more carefully and youll see why his vas looks the way it does. He was clever and found a way to define the vas current, try define it on your design.

In your case the mirror you hae there will help but i dont think it will overcome the problem completly
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Old 14th January 2009, 06:10 PM   #146
catalin is offline catalin  Romania
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"output offset will be all over the place,"
Explain pls
Thank you
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Old 14th January 2009, 06:27 PM   #147
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catalin,
for a more favorable distortion pattern. Then I would use the resources to linearize the open-loop.
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Old 14th January 2009, 06:32 PM   #148
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Here is some info by members with much more theory knowledge than me and some diffrent ways to look at the problem. Theres many more threads I can refer to. The Jlh solution works but it has some flaws too, read the whole thread.

Unstable VAS current in amp from Slone book
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Old 14th January 2009, 06:34 PM   #149
catalin is offline catalin  Romania
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Quote:
Originally posted by Lumba Ogir
catalin,
for a more favorable distortion pattern. Then I would use the resources to linearize the open-loop.

I think that distortion is less(crossover,pozitive and negative rail have their way,etc,) with complementary design and a lot other advantages .
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Old 14th January 2009, 06:46 PM   #150
catalin is offline catalin  Romania
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Quote:
Originally posted by homemodder
Here is some info by members with much more theory knowledge than me and some diffrent ways to look at the problem. Theres many more threads I can refer to. The Jlh solution works but it has some flaws too, read the whole thread.

Unstable VAS current in amp from Slone book

It' not like his problems.
In that design the current vas don't change with the vcc.just one aspect
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