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Old 8th May 2012, 12:02 PM   #551
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LC i think "Lazy Cat" is absolutly not appropiate, "Crazy Cat" fit you as a surgeon glove on a hand....

Marc
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Old 8th May 2012, 12:26 PM   #552
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Did a simple sim of the initial basic schematics and it showed in the ballpark of 2ohm with 1302/0281 and 557/547. But you seem to have a little higher openloop gain now.

So basically this is a transconductance amp that relies on NFB only for lowering Zout?
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Old 8th May 2012, 01:39 PM   #553
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The front act as an current source in this case and cannot feed enough current to the output BJT's. But add a output driver and the output impedance will Fall.
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Old 8th May 2012, 02:19 PM   #554
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You are so right, I should maybe have used MOSFET output device when I copied one of the too far simplified schematics.
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Old 8th May 2012, 08:01 PM   #555
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Hi LC, i plane to install a switchable input cap. What will be the best value for?

Marc
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Old 8th May 2012, 08:06 PM   #556
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by revintage View Post
You are so right, I should maybe have used MOSFET output device when I copied one of the too far simplified schematics.
Actually, the bjt set with predriver and 0.1R emitter resistor Will give you lower distortion because of higher transconductance.
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Old 8th May 2012, 09:51 PM   #557
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Quote:
Originally Posted by Idefixes View Post
Hi LC, i plane to install a switchable input cap. What will be the best value for?

Marc
At 10 kOhm input impedance I suggest to use 22 uF or vice versa 10 uF at 22 kOhm (have to change) input resistor, to get 4,5 Hz/-4dB high pass roll off. Also you need to have input side of the capacitor connected to GND via 1 MOhm resistor to define zero DC potential and to have no clicks by switching AC/DC coupling.
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Old 9th May 2012, 08:45 AM   #558
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Quote:
Originally Posted by Joachim Gerhard View Post
When the transistors are ok the circuit in post 1 works right away.
Hi Gerhard

I own you a great apology not to come to your booth at High End, the reasons are combined (bunch of crazy audiophiles lost orientation sense in a "playground", tight time schedule - one transport ...) and not completely justified I know. Please forgive and hopefully we'll stay cooperative as we were before.

Kind regards Andrej
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Old 9th May 2012, 08:48 AM   #559
sonnya is offline sonnya  Denmark
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Gerhard, what did you display??
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Old 9th May 2012, 09:47 AM   #560
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No problem LC, i was not always at the booth anyway.
I designed a phono amp with tone controls for Fast Audio. The name is Tanzmusik.
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