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Stewart Pinkerton wrote:
On Mon, 14 Mar 2005 00:49:21 -0600, (John Byrns) wrote:
In article , Stewart Pinkerton
wrote:
On Sun, 13 Mar 2005 01:57:31 -0500, Jon Yaeger
wrote:
in article , John Byrns
at wrote on 3/12/05 8:17 PM:
I have scored the three current entrants in the KISS amp design
competition
The competition to see if a reasonable solid state facsimile of Andre's
300B KISS amp could be designed.
What 'competition' is this?
And who elected you judge?
Everyone else took a step backwards, so I was elected. Somebody had to
compare the various designs, your comments/criticisms on my judging are
welcome.
For scoring purposes I considered NFB to exist only if two or more stages
were enclosed in a NFB loop, local NFB as in a triode tube or transistor
emitter follower, was not counted as NFB. Stewart's KISASS design failed
the NFB test because two stages, Tr1 & Tr2 were enclosed in the single NFB
loop formed by R7.
That is incorrect.
How so? Are you saying that my judging criterion relative to NFB around
two or more stages is incorrect, or that your KISASS design doesn't have
NFB around two stages?
KISASS doesn't have feedback around two stages.
Tr1 & Tr2 constitute a two stage amplifier with the load consisting of the
150 Ohm resistor R5 paralleled with the input of the output stage.
Yes.
The
load current flows through the 24 Ohm resistor R7 in the emitter circuit
of Tr2, R7 is also in series with the input signal driving the base
emitter circuit of Tr1. This constitutes and obvious case of a NFB loop
encompassing more than a single stage.
What? That's madness! Besides, Tr1 is only there to provide a
conventionally high input impedance. If you have a CD player with a
decent output stage, Tr1 can be removed.
Why not use a j-fet?
Patrick Turner.
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Stewart Pinkerton | Music is Art - Audio is Engineering
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