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Stee 25th June 2011 10:00 PM

Common base VAS
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this amplifier is a modification of a-680
is an inverting amplifier
so don't need current mirror
I have connected jfet source on GROUND as tube's design
that works very fine:p

DIYGene - Electronics DIY, Hi Fi , amplifier

CBS240 26th June 2011 02:22 AM

If you take away the summing node and make it gnd, the diff amp is no longer a diff amp. You have two common source amplifiers, with different transfer characteristics and distortion spectrum. If it works it works, but it is nothing particularly special. Symmetrical folded cascode VAS. Is there a different perception of the sound after swapping the input stage?

Stee 26th June 2011 09:17 AM

yes of course
2 Attachment(s)
never listening a better amplifier :):):)
probably because don't have differential stage
or because have ground reference like triode (not so easy to found)
also because I have simulate internal balanced power supply
with two transformers in input
one of these do an inverting phase
and the same again in output polarity:cool:

in other words

to get the advantage of balanced sound
without risk of adding errors
just take a power transformer as input converter

you can simulate the natural balance of power supply like true balanced AMP
inverting a channel input (secondary polarity) and output (loudspeaker)

Stee 26th June 2011 03:43 PM

see a ZOOM
1 Attachment(s)
of input and VAS stages

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