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Old 6th April 2013, 07:21 PM   #71
Tazzz is offline Tazzz
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Here is another long dead citation 12 that's in the process of coming back to life with complimentary mosfet outputs.
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Old 6th April 2013, 07:33 PM   #72
nrg2009 is offline nrg2009  United States
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Tazzz, where did you find that board?
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Old 6th April 2013, 07:35 PM   #73
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I made them. =)
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Old 6th April 2013, 10:56 PM   #74
nrg2009 is offline nrg2009  United States
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Awesome! Care to sell any spare boards?
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Old 8th April 2013, 09:39 PM   #75
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Seems to work!
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Old 8th April 2013, 09:41 PM   #76
nrg2009 is offline nrg2009  United States
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Those numbers are better than awesome! Great job. Thanks for sharing those pictures. A masterpiece and revival of a classic design.
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Old 21st April 2013, 11:02 AM   #77
Tazzz is offline Tazzz
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I strongly advice Replacing R1 with a current source for the input diff pair.

Its obvious now when you look at the schematic that the input diff pair cannot control the VAS when the voltage across R1 is less then half the supply voltage, due the resistive load R2 (sized to split the current equally in the diff pair at normal operation)

Simply put when the supply voltage bellow about half the supply voltage Q3 is turned off and R3 and R4 acts as pull up on the Q6 putting what is left in the reservoir caps across the speakers...
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Old 21st April 2013, 11:15 AM   #78
Cobra2 is offline Cobra2  Norway
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citation 12 mos fet citation 12 mos fet
Quote:
Originally Posted by Tazzz View Post
I made them. =)
Would like a pair too!

Arne K
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Don't believe everything you think...
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Old 21st April 2013, 03:19 PM   #79
nrg2009 is offline nrg2009  United States
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Quote:
Originally Posted by Tazzz View Post
I strongly advice Replacing R1 with a current source for the input diff pair.

Its obvious now when you look at the schematic that the input diff pair cannot control the VAS when the voltage across R1 is less then half the supply voltage, due the resistive load R2 (sized to split the current equally in the diff pair at normal operation)

Simply put when the supply voltage bellow about half the supply voltage Q3 is turned off and R3 and R4 acts as pull up on the Q6 putting what is left in the reservoir caps across the speakers...
Wow, great catch!
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Old 21st April 2013, 04:34 PM   #80
Tazzz is offline Tazzz
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Quote:
Originally Posted by Cobra2 View Post
Would like a pair too!

Arne K
Certainly! I have several boards just shoot me a PM, I can also include curve traced transistors for the input pair (2SA970).
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