John Curl's Blowtorch preamplifier part II

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diyAudio Member RIP
Joined 2005
Attached is one designers jfet/ne5534 implementation?
I posted it one time in a diyaudio thread and one person commented that it can't be any good for audio, it is only good for a THD analyzer use :)
One day I will lay it out in smt to give it a try. It so hard to judge the differences between these low THD designs.
Good luck getting the JFETs.
 

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diyAudio Member RIP
Joined 2005
I've had obsolescence on my mind of late. I no sooner tell a contract manufacturer how much I hate single-sourced components than the options evaporate.
And I really should have said discontinuance, not obsolescence. The latter means something is no longer desired, which is not the case most of the time with electronic parts --- unless it applies to the decision-makers at the parts houses.
 
Attached is one designers jfet/ne5534 implementation?
I posted it one time in a diyaudio thread and one person commented that it can't be any good for audio, it is only good for a THD analyzer use :)
One day I will lay it out in smt to give it a try. It so hard to judge the differences between these low THD designs.

http://www.richardhess.com/manuals/Amber3501.pdf

The rest of the manual (on a quick look) is also not bad for theory of operation.
 
why resurrect these circuits - recent op amps have much better output stages with faster, better matched complementary Q

show discrete fet input with something from only the last 20 years, please

yes you don't have as many options today to cut off/bypass the input in the following op amp - but many can be had so many times faster that you wouldn't need to to exceed a 5534 composite circuit
 
awkward wording on my part - I was trying to ask why don't people show discrete fet inputs with modern op amp following them

trying to point out that the modern op could be selected to be so much faster than a 5543 with disabled input replaced by discrete fets that you could still compensate the discrete fet+series modern op amp multiloop to give a faster composite amp than the fet+5534 despite not being able to bypass the modern part's input stage, having to accept the "extra" stage in series

get the discrete fet noise - and modern op amp output
 
I meant my comment originally to mildly take a jab at the 5532 haters. Of course, updating these old circuits with modern, high speed opamps would be prudent, even without bypassing the input pair. The biggest benefit I could imagine is stability (distortion/etc has got to be beyond audible).
 
why resurrect these circuits
Certainly provides me with some entertainment :) in my retirement.
I was trying to ask why don't people show discrete fet inputs with modern op amp following them
As Bob Cordell documented in the lsk489 app note. More circuits for me to try out. pcbway has the $13 per 100x100mm pcb special for 2 layer, how cheap is that to make some toys to play with!!
 
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