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Old 5th June 2005, 07:06 PM   #1
vAD is offline vAD  Russian Federation
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Default Please comments

Hello, people, i'm a rookie here . So don't be cruel to me. Let me show my diy amplifier.
I Will be very grateful if you'll send some comments, especially on values.
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Old 5th June 2005, 07:39 PM   #2
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Well, wheres the amp? We're pretty smart here but cannot read your mind......
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Old 5th June 2005, 08:14 PM   #3
vAD is offline vAD  Russian Federation
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Default Please comments

Hello, people, i'm a rookie here . So don't be cruel to me. Let me show my diy amplifier.
I Will be very grateful if you'll send some comments, especially on values.
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Old 5th June 2005, 11:31 PM   #4
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Just some really quick thoughts....

It looks to me like your volume control isnt wired correctly. It shorts the output of the opamp.

Your Q1 to Q4 looks interesting. I never see a topology like that. Do you have a reference about it?

I know that some mosfet amps have just a resistor for bias but they really do have +ve temp coeff at low current. You probably do need a Vbe multiplier there.

You have lots of stages. Each stage contributes at least a HF pole which means your HF response gets really complicated. This can make an amp hard to stabilise but I dont know for sure.

Doug
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Old 5th June 2005, 11:31 PM   #5
vAD is offline vAD  Russian Federation
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And one more, very simple amp.[IMG]http://[/IMG]
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Old 6th June 2005, 03:21 AM   #6
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Your Q1 to Q4 looks interesting. I never see a topology like that. Do you have a reference about it?

I saw that topology in use with a vacuum tube implementation. Unforch, I can't seem to find it again.
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Old 7th June 2005, 05:35 AM   #7
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i think i have seen such a schematic (something alike) in LT1166 applications

Gajanan Phadte
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Old 7th June 2005, 06:55 AM   #8
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Default deleveld

Yes volume control wired correct also works without increase DC output.
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Old 7th June 2005, 06:55 AM   #9
vAD is offline vAD  Russian Federation
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No! On question Q1 to Q4, references are not present, it has turned out after perusal of magazines about audo etc., many thanks to Nelson Pass, the first amplifier which has earned the second was ZEN, Citation12.
I am sorry for the English I write with the translator.
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Old 7th June 2005, 07:56 AM   #10
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Hallo vAD
I advise to change the 'diamond' Q1-Q4. I mean to NOT connect collectors of previous stage with emitters of the next stage.
This may cause higher offset and power supply noise.
I would connect collectors dirctly with rails. Another things:
-I think you don't need R55/56
-if you modify diamond as I said probably you won't need offsset pot
-maybe higher idle current in driver stage?
-probably you will need frequency compensation: maybe a small (say:100p) capacitor from bias pot to the ground
-small resitor on q1/2 emitters would be a voltage devider to prevent next stage from working in class (a)b

overal it look pretty nice to me-topology is OK!!!
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