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In Reply to: Re: interesting posted by Henry Pasternack on April 13, 2004 at 11:20:59:
Henry wrote::::The output stage is symmetrical, even if the drive isn't.:::
if the "drive" (depending on how we define "drive") is not symmetrical... how pray tell would the output be "symmetrical"....
and everyone is using the term "symmetrical" as if it's an "all or nothing" proposition....
for istance the basic concepts of the 'compact' amp (advanced versions NOT.... NOT..... NOT.... the favorite whipping boy that was publshed in 1961) are practically the same as Henry's fave design he referred to earlier with the exception that his favorite is much more complex than an advanced compact design...
but back to symmetrical.... read the words written by Paul Joppa earlier in this thread..... in the box below....
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The idea of using a large shared cathode impedance to force differential currents is very old; I don't know when the long-tailed pair was first described but I'd expect it to be in the twenties.
Today, with very high impedance current sources, it is possible to force differential behavior to great precision, probably 0.1% or better. Whether you call it super-deep Class A or differential or whatever....
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the compact with a stiff impedance source in the cathode circuit does promote or acheive a very high degree of balance in the phase inversion....perhaps we should measure the phase inversion and the balance instead of hypothesizing...
again... anyone interested I would go to Yeo's site and check out ALL the compact pages... or check out several of the other posts in this thread where folks have built the amp....
and argue the semantics of what is or isn't a differential... but... such arguments appear to me to be semantical and to quote Joppa once again,
:::Hard to tell the apples from the oranges here.::::
too bad Norman crowhurst isn't around... or maybe he did write something on this... as he had one piece as I recall that was devoted to exploring several of the various phase splitting schemas...sorry, henry, but there is no clarity being added or obtained in this discussion at this point....
MSL
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Follow Ups
- Re: interesting - MQracing 14:15:49 04/13/04 (7)
- Re: interesting - Henry Pasternack 16:11:56 04/13/04 (3)
- Re: interesting - MQracing 18:04:41 04/13/04 (2)
- Re: interesting - Henry Pasternack 20:37:06 04/13/04 (1)
- Re: interesting - arend-jan 00:42:18 04/14/04 (0)
- Paul, please correct me if I'm wrong... - Scholl 14:46:07 04/13/04 (2)
- Re: Paul, please correct me if I'm wrong... - MQracing 15:27:04 04/13/04 (1)
- Some preliminary tests - Scholl 08:01:58 04/15/04 (0)
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