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Old 3rd September 2011, 04:14 PM   #2621
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Yes, sure, this is more or less the quintessential com.diff. structure. I would use the laterals at the output driving the speaker with the drains though. You will observe better stability with a speaker load. Lazy Cat mentioned that in his thread at the beginning when his amp was still simple. I mentioned that several times too but it went unrecognized.
What i really need is a little 25W class A amp so we could open a thread " Simple Class A amp with laterals in common source configuration ". What do you think.
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Old 3rd September 2011, 04:41 PM   #2622
MiiB is offline MiiB  Denmark
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I think that the simple lazy-cat is already there...

I have made PCB's for a scaled version..with Transistor current dumping ala Adyton for the output...plan on running it at 56 V rails, Get 10 PCB's this coming week.....could be possible to tweak the PCB a bit.. and cut off the current dumping part..Then your 30 W is there...

but driving from the drain is surely interesting..

Last edited by MiiB; 3rd September 2011 at 04:51 PM.
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Old 3rd September 2011, 04:44 PM   #2623
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Fine, you are a busy man. That could be something for me. Could you post the circuit diagram again here ? That other thread got me confused.
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Old 3rd September 2011, 06:05 PM   #2624
MiiB is offline MiiB  Denmark
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Give me a day or two, then I'll post a couple of schematics.
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Old 3rd September 2011, 06:17 PM   #2625
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Thanks Michael, you are really in the groove.
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Old 5th September 2011, 12:57 AM   #2626
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Tonight i put the PEN circuit in my system. The only thing i can say is that it plays music and it is low noise. I can listen only quiet at this time in the night and after a lot of component swapping i have some trouble on one channel of my resident MM phono stage.
I will sort it out tomorrow.
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Old 5th September 2011, 03:27 AM   #2627
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I found a power amp circuit that is a blueprint of some of my phono circuits i published here.
Scary ? no
Attached Images
File Type: jpg current feedback amp.jpg (51.3 KB, 299 views)
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Old 5th September 2011, 09:03 AM   #2628
MiiB is offline MiiB  Denmark
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Hi Joachim.. Been fiddling around with the drain tapped poweramp...an can't seem to get i working properly...well it seems like all working points are looking nice.. current in the output fully adjustable..running a nice current (5mA) in the input cascode....But performance is really bad with 2.5% distortion even at low swings...

Will have to look more into this.. Why do you want to take the signal off the Drain..??
I mean the speaker return currents has other ways into the amplifier than though the internal mosfet-diodes...here it runs right into the feedback network..
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Old 5th September 2011, 11:29 AM   #2629
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Maybe this idea to go out the drains does not work with Lazy Cats input stage. I would prefer that connection because of simplicity. Also a lateral Fet is a very good constant current source. I am concerned about the stability of the amp into a complex load. I see here many amps that have THD of less then 0.001% simulated or measured on a dummy load so this problem is solved. For example the TMC blameless that was published in Linear Audio 1. It uses only a few parts and is cheep to make. So why should we design another amplifier ? Self is the champion on low TDH versus cost already. Connected to a real speaker things are not so rosy any more. Anyway Michael, go ahead and design something that works for you. I am curious to investigate it.
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Old 5th September 2011, 02:36 PM   #2630
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The PEN circuit is now working in Stereo. I had an offset problem on one channel of my MM stage. It was caused by a small uninsulated copper wire that was conecting Pin 4 to Pin 3 of my JG-Self MM. The PEN is quiet. I will do more listening today.
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