XPost: sci.electronics.design   
   From: sophi.2@invalid.org   
      
   On 3/3/2011 12:04 AM, John Larkin wrote:   
   > On Wed, 02 Mar 2011 22:45:48 -0600, John - KD5YI   
   > wrote:   
   >   
   >> On 3/2/2011 10:24 PM, John Larkin wrote:   
   >>> On Wed, 02 Mar 2011 22:06:41 -0600, John - KD5YI   
   >>> wrote:   
   >>>   
   >>>> On 3/2/2011 8:52 PM, John Larkin wrote:   
   >>>>> On Wed, 02 Mar 2011 20:40:27 -0600, John - KD5YI   
   >>>>> wrote:   
   >>>>>   
   >>>>>> On 3/2/2011 8:32 PM, John Larkin wrote:   
   >>>>>>> On Wed, 2 Mar 2011 17:59:58 -0800 (PST), Bill Sloman   
   >>>>>>>      wrote:   
   >>>>>>>   
   >>>>>>>> On Mar 3, 2:11 am, John Larkin   
   >>>>>>>>      wrote:   
   >>>>>>>>> On Wed, 02 Mar 2011 18:36:25 -0600, John Fields   
   >>>>>>>>>   
   >>>>>>>>>   
   >>>>>>>>>   
   >>>>>>>>>      wrote:   
   >>>>>>>>>> On Wed, 02 Mar 2011 08:40:42 -0800, John Larkin   
   >>>>>>>>>>      wrote:   
   >>>>>>>>>   
   >>>>>>>>>>> I've always sort of liked the classic "GE" tape head/mic preamp   
   >>>>>>>>>>> circuit:   
   >>>>>>>>>   
   >>>>>>>>>>> ftp://jjlarkin.lmi.net/GEcircuit.jpg   
   >>>>>>>>>   
   >>>>>>>>>>> but it occurred to me that it might also make a nice headphone   
   amp...   
   >>>>>>>>>   
   >>>>>>>>>>> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG   
   >>>>>>>>>   
   >>>>>>>>>>> Audio tends to be nonsense, but at least the audio guys have fun   
   >>>>>>>>>>> playing with circuits, whether they make a lot of sense or not.   
   >>>>>>>>>   
   >>>>>>>>>>> John   
   >>>>>>>>>   
   >>>>>>>>>> ---   
   >>>>>>>>>> Even though you scorn and ridicule audio, there's nothing wrong with   
   >>>>>>>>>> anyone seeking perfection there, just as there's nothing wrong with   
   >>>>>>>>>> your search for perfection in the genre which pleases _you_ to   
   pursue.   
   >>>>>>>>>> So, speaking of fun, why don't you do a complete design and assign   
   >>>>>>>>>> values to the circuit components and identify the semiconductors?   
   >>>>>>>>>   
   >>>>>>>>> You're not playing the game. You are sitting in the henhouse,   
   clucking   
   >>>>>>>>> about the people who do.   
   >>>>>>>>   
   >>>>>>>> He's not playing your game, which involves telling John Larkin how   
   >>>>>>>> cute his circuits are.   
   >>>>>>>   
   >>>>>>> He's not designing circuits, which is what this newsgroup is about.   
   >>>>>>>   
   >>>>>>> You aren't either. Both of you start to cluck and peck when people do   
   >>>>>>> design circuits. No surprise.   
   >>>>>>>   
   >>>>>>>   
   >>>>>>>>   
   >>>>>>>>>> Or is that legwork _we're_ supposed to do in order to flesh out your   
   >>>>>>>>>> divine revelation?   
   >>>>>>>>>   
   >>>>>>>>> Chickenleg work!   
   >>>>>>>>   
   >>>>>>>> It's half the story - a few component values make it a lot easier to   
   >>>>>>>> work out what a circuit is doing.   
   >>>>>>>   
   >>>>>>> You can't look at a circuit this simple and see what it's doing? OK,   
   >>>>>>> no surprise.   
   >>>>>>>   
   >>>>>>> John   
   >>>>>>   
   >>>>>> Well, I thought designing a circuit included supplying component values.   
   >>>>>> No?   
   >>>>>   
   >>>>> I posted topologies. Values can be scaled to the application, but you   
   >>>>> need a topology first. If I were actually going to build this, for   
   >>>>> money, of course I'd have to define specs and then compute values.   
   >>>>> That's just grunt work.   
   >>>>>   
   >>>>> John   
   >>>>   
   >>>> Not really. I have a few circuits I could throw out and claim that they   
   >>>> are topologies and you would not be able to use them without values.   
   >>>> Granted, mine are more complex than the one being discussed, but I'm   
   >>>> hoping to make a point.   
   >>>>   
   >>>> John (not Larkin)   
   >>>>   
   >>>   
   >>> I think circuit topologies are fun to play with. Lots of textbooks   
   >>> show, and discuss, circuits without explicit values. Once you have a   
   >>> topology, then you can proceed to specs and component values.   
   >>>   
   >>> If you think all circuits should be posted with values, post some.   
   >>>   
   >>> John   
   >>   
   >> You are correct, John. Now you have a topology. Please post the   
   >> component values.   
   >>   
   >> Thanks,   
   >> John   
   >   
   > Given i/o specs, the DC analysis is simple. But there are two AC   
   > aspects that are sort of interesting: the lf response, and loop   
   > stability. I'm sort of disappointed that nobody has commented on   
   > either.   
   >   
   > As I'm disappointed in how many people want to whine and cluck about   
   > personalities, and avoid actually discussing electronics.   
   >   
   > John   
      
   Okay, I put some values to it. It looks like a nice circuit, I admit.   
   Good gain, low distortion, reasonable input impedance. Mind you, I   
   didn't try to optimize it. I did notice that the feedback took higher   
   than expected resistance and I was a bit surprised that the emitter   
   capacitor of the output stage made the response do a camel hump at the   
   beginning if too high.   
      
   So, critique away. I might learn something.   
      
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