Please comments

vAD · 5th June 2005, 07:06 PM

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.

deleveld · 5th June 2005, 07:39 PM

Well, wheres the amp? We're pretty smart here but cannot read your mind......

vAD · 5th June 2005, 08:14 PM

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.

deleveld · 5th June 2005, 11:31 PM

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

vAD · 5th June 2005, 11:31 PM

And one more, very simple amp.[IMG]http://[/IMG]

Miles Prower · 6th June 2005, 03:21 AM

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.

gmphadte · 7th June 2005, 05:35 AM

i think i have seen such a schematic (something alike) in LT1166 applications

Gajanan Phadte

vAD · 7th June 2005, 06:55 AM

Yes volume control wired correct also works without increase DC output.

vAD · 7th June 2005, 06:55 AM

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.

darkfenriz · 7th June 2005, 07:56 AM

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!!!

6th June 2005, 03:21 AM	#6
Miles Prower diyAudio Member Join Date: May 2005 Location: USA Blog Entries: 2	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. __________________ There are no foxes in atheistholes www.dolphin-hsl.com

7th June 2005, 06:55 AM	#8
vAD diyAudio Member Join Date: Apr 2005 Location: Russia	deleveld Yes volume control wired correct also works without increase DC output.

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5th June 2005, 07:39 PM	#2
deleveld diyAudio Member Join Date: Apr 2002	Well, wheres the amp? We're pretty smart here but cannot read your mind......

5th June 2005, 11:31 PM	#4
deleveld diyAudio Member Join Date: Apr 2002	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

7th June 2005, 05:35 AM	#7
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	i think i have seen such a schematic (something alike) in LT1166 applications Gajanan Phadte

7th June 2005, 07:56 AM	#10
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	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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