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#371 |
diyAudio Member
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Something like this,Hugh?
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#372 |
diyAudio Member
Join Date: Sep 2001
Location: Melbourne, Australia
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Precisely, Pavel.
Revealed to me now in sims, at last, I have something to hang my hat upon. Hugh |
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#373 |
diyAudio Member
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And,
the harmonic profile has some dependency on signal amplitude and on frequency, another property of tubes I believe. All in all, done very nicely, the hallmark of a great amp.
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"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig. |
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#374 | |
diyAudio Member
Join Date: Dec 2008
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IE the customers are happy with the ending. And that is the main thing. |
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#375 | |
diyAudio Member
Join Date: May 2007
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Just because an amplifier cct does not have a CC or Current mirror, does not invalidate its performance..Consider this scenario, even if you match very closely a differential I/P pair you will still have a common mode difference which in the typical diff pair is complicated because it is across two different transistors and the assumption is that what is fed back via the feedback loop is identical to what is fed into its I/P but for the phase difference, unfortunately because the loudspeaker produces an impedance variation, which in turn is also fed back to the diff pair albeit in reduced amplitude, it is assumed that this is all somehow balanced out alas this is not quite true because the impedance plot of the loudspeaker represents a changing phase which is fed to the feedback side of the diff pair, now the diff pair has to cope with this factor plus the common mode errors, now in the Bailey cct the I/P and the feedback is applied to a single transistor, so there is no common mode error, the control is also instant being in the same electron stream and this may account for some of the perceived accuracy of this topography, Dr Bailey who also designed the Bailey line transmission line back in the 60's, originally conceived this amp as a 30watt job using rather slow transistors by todays standards but after resolving a bad case of early effect in the main driver transistor was eventually able to produce a square wave at 50khz with little error he was using an RCA 40362 in the driver transistor for low cob and small early effect.. Of course there are better devices today..You can have a good amp with a CCS and current mirror if you remember to design for very high damping factors as this will reduce the amount of loudspeaker impedance variations getting back into the feedback loop.Meridian did much work on this reflected impedance over 25 years ago to deal with this type of problem..Its all well known..and it may be why some people like amps with no overall neg feedback..its all about proper design..Also J.Linsley Hood's class A amps of 15watts to 30watts also used a single I/P transistor and it was well thought of for its clarity.. In its day the Bailey amp was highly regarded although it was a class B, despite which its distortion at full power and throughout the freq range was well under 0.1% regards Humble |
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#376 |
diyAudio Member
Join Date: May 2008
Location: Smoky Mountains , Tennessee
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Or like this... This topology can go ALL the way.
OS
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